Coronavirus Resource Center

As coronavirus continues to spread, many questions and answers

The continuing, rapid spread of the SARS-CoV-2 virus has sparked alarm worldwide. Countries around the world are grappling with surges in confirmed cases, hospitalizations, and deaths. Preventive measures such as physical distancing and masks to slow the spread of coronavirus have created a new normal in many places. Health care workers and hospitals have once again ramped up capabilities to care for large numbers of people made seriously ill by COVID-19.

Meanwhile, scientists continue to explore potential treatments and prevention strategies. In December 2020, the FDA granted emergency authorization to two COVID-19 vaccines. At least two other vaccine candidates are close behind. The first vaccines were given in mid-December, with healthcare workers and residents of long-term care facilities among the first to receive the injections.

Below, you'll find answers to common questions all of us are asking. We will be adding new questions and updating answers as reliable information becomes available. Also see our blog posts featuring experts discussing coronavirus and COVID-19 and our glossary for relevant terms.

New questions and answers

What side effects can I expect from the COVID vaccine?

Minor side effects are common after COVID-19 vaccination. Almost everyone experiences arm pain at the injection site. Other symptoms can include low grade fever, body ache, chills, fatigue, and headache.

You can expect to feel better within 24 to 48 hours. Some people feel too unwell to go to work or perform their usually daily activities during this period. Contact your doctor if your symptoms have not improved by the third day.

Moving your sore arm around may help to relieve discomfort. If you have a fever, drink plenty of fluids. Over the counter pain relievers like ibuprofen or acetaminophen can also help with fever, pain, and other discomfort. However, it's best to not take a pain reliever right before getting your shot, because there is a chance this could blunt your immune response.

The good news: These side effects are a sign that the vaccine is working and that your body is building an antibody response. The currently available vaccines require two shots, and side effects are more likely to occur after the second shot.

Will the COVID-19 mRNA vaccines work against the new coronavirus variants?

Early evidence suggests that the Pfizer/BioNTech mRNA vaccine is effective against the new coronavirus variants. Testing of the Moderna mRNA vaccine against the new variants is underway.

The two new variants are more contagious than previous SARS-CoV-2 variants, but they do not appear to be deadlier. One, called B.1.1.7, was first detected in the United Kingdom. The other, called B.1.351, originated in South Africa. Both variants have now been detected in countries around the globe.

Both variants contain mutations on the virus's spike protein. Spike proteins on the surface of the SARS-CoV-2 virus bind to and allow the virus to enter human cells. Interestingly, both variants share a key mutation (called N501Y) on the spike protein, which allows the virus to bind more tightly to human cells. This mutation makes the new variants more contagious than previous SARS-CoV-2 variants.

To test the effectiveness of the Pfizer/BioNTech mRNA vaccine against the new variants, researchers created a virus with the N501Y mutation. They then took blood samples from 20 participants enrolled in their vaccine trial and exposed the samples to the mutated virus. The participants' blood contained human cells as well as antibodies made in response to the Pfizer/BioNTech vaccine. They found that the antibodies blocked the mutated virus from infecting human cells as effectively as it blocked the virus without the mutation.

More study is needed to see if these results hold up in real world conditions. It's also not known how long this protection may last, and whether the vaccines will work against other mutations found in these variants.

Should I get the COVID-19 vaccine if I already had COVID-19?

Even people who have already gotten sick with COVID-19 may benefit from the vaccine, according to the CDC.

Here's what we know. COVID-19 can lead to serious illness and long-term complications, even in younger people and those without underlying medical conditions. We also know that it's possible for someone who has already had COVID-19 to be re-infected, though this is not common.

On the other hand, we don't know how long natural immunity to COVID-19 — the protection that results from having been sick — lasts. It's not clear if the strength or duration of natural immunity varies based on the severity of the initial illness. We also don't know how long immunity conferred by vaccines lasts.

During the initial deployment of the vaccine to front line workers and people in long-term care facilities like nursing homes, people eligible for the vaccine will get it regardless of whether or not they were previously infected. They are not being tested for antibodies prior to vaccination.

As scientists learn more about natural immunity after COVID illness, vaccination criteria based on the presence of antibodies may play a role in the future.

Once I get the COVID-19 vaccine, can I stop taking other precautions?

The vaccine will protect you from getting sick, but it may not prevent you from infecting others. That's why, at least for now, you should continue wearing a mask and physically distancing from others, even after you get your shot.

Clinical trials of the Pfizer/BioNTech and Moderna vaccines found that both do a good job preventing symptomatic COVID-19 disease, including severe COVID-19. However, the trials did not measure whether a person who is vaccinated is less likely to spread the virus to someone else.

It's possible that the vaccines protect against COVID-19 disease by preventing a person from becoming infected. However, it's also possible that the vaccine protects a person from getting sick but does not prevent the virus from replicating in that person's nose and throat.

Does that mean there's enough virus in your nose and throat to infect someone else? Not necessarily. But we need more research to know for sure.

Where does that leave us? If you're among the first groups of people to get vaccinated, it's best to continue wearing masks and maintaining physical distance in order to protect others who haven't yet gotten the vaccine.

What do we know about the Moderna COVID-19 vaccine that the FDA has authorized for emergency use?

On December 18, 2020, the FDA granted emergency use authorization (EUA) to an mRNA COVID-19 vaccine developed by Moderna in collaboration with scientists from the NIH. The vaccine is approved for use in people 18 years and older. This is the second COVID-19 vaccine authorized for use in the US. (The Pfizer/BioNTech vaccine received EUA during the prior week.)

The FDA granted EUA based on their own analysis of efficacy and safety data as well as on the recommendation made by the Vaccines and Related Biological Products Advisory Committee (VRBPAC). VRBPAC is a group of outside experts in infectious disease, vaccinology, microbiology, immunology, and other related fields.

In briefing documents submitted to the FDA, the Moderna vaccine showed an overall efficacy of 94.1% in preventing COVID-19. This study enrolled 30,400 adults; half received the vaccine, half received a saltwater placebo shot. There were 196 infections among the study participants. Of these, 185 were in the placebo group and 11 were in the vaccine group. All 30 cases of severe COVID occurred in the placebo group, strongly suggesting indicating that the vaccine reduces risk of severe illness.

The vaccine was similarly effective in people older and younger than 65, in men and women, in people with and without medical conditions that put them at high risk for severe illness, and in different racial and ethnic groups.

The most common vaccine side effects were pain at the injection site, fatigue, headache, muscle pain, joint pain, and chills.

This vaccine requires two doses, spaced four weeks apart. We do not yet know how long immunity from this vaccine will last.

The Moderna vaccine contains synthetic messenger RNA (mRNA), genetic material that enters human cells and instructs them to produce the spike protein found on the surface of the SARS-CoV-2 virus. The body recognizes the spike protein as an invader and produces antibodies against it. Soon after, the cell breaks down the mRNA into harmless pieces. If the antibodies later encounter the actual virus, they are ready to recognize and destroy it before it causes illness.

Unlike the Pfizer vaccine, which requires ultracold storage, the Moderna vaccine can be stored at normal freezer temperatures. This may allow for wider distribution to pharmacies and other facilities that are not equipped for ultracold storage.

Will the COVID vaccine prevent me from infecting others?

The answer is, we don't know.

Clinical trials of the Pfizer/BioNTech and Moderna vaccines found that both do a good job preventing symptomatic COVID-19 disease, including severe COVID-19. However, the trials did not measure whether a person who is vaccinated is less likely to spread the virus to someone else.

It's possible that the vaccines protect against COVID-19 disease by preventing a person from becoming infected in the first place. However, it's also possible that the vaccine protects a person from COVID-19 illness, but does not prevent a person from becoming infected. In other words, a vaccinated person may have replicating virus in their nose and throat even if they are protected from becoming sick.

But does that mean that you have enough virus in your nose and throat to infect someone else? Not necessarily. It's possible that the immune response triggered by the vaccine, which protects you from becoming sick, also reduces the amount of virus in your nose and throat to a point where you are unlikely to spread it to someone else. But we need more research to know for sure.

The bottom line? If you're among the first groups of people to get vaccinated, it's best to continue wearing masks and maintaining physical distance in order to protect others who haven't yet gotten the vaccine.

Could an mRNA vaccine change my DNA?

An mRNA vaccine — the first COVID-19 vaccine to be granted emergency use authorization (EUA) by the FDA — cannot change your DNA.

mRNA, or messenger RNA, is genetic material that contains instructions for making proteins. mRNA vaccines for COVID-19 contain man-made mRNA. Inside the body, the mRNA enters human cells and instructs them to produce the "spike" protein found on the surface of the COVID-19 virus. Soon after a cell makes the spike protein, the cell breaks down the mRNA into harmless pieces. At no point does the mRNA enter the cell's nucleus, which is where our genetic material (DNA) lives.

The immune system recognizes the spike protein as an invader and produces antibodies against it. If the antibodies later encounter the actual virus, they are ready to recognize and destroy it before it causes illness.

What do we know about the Pfizer/BioNTech COVID-19 vaccine that the FDA has authorized for emergency use?

On December 11, 2020, the FDA granted emergency use authorization (EUA) to an mRNA COVID-19 vaccine developed by Pfizer and BioNTech. The vaccine is approved for use in people 16 years and older. This is the first COVID-19 vaccine authorized for use in the US.

The FDA granted EUA based on their own analysis of efficacy and safety data as well as on the recommendation made by the Vaccines and Related Biological Products Advisory Committee (VRBPAC) on December 10th. VRBPAC is a group of outside experts in infectious disease, vaccinology, microbiology, immunology, and other related fields.

Results from the Pfizer/BioNTech vaccine trial were published in the New England Journal of Medicine. The data showed that the vaccine reduced the risk of COVID-19 by 95%. The trial enrolled nearly 44,000 adults, each of whom got two shots, spaced three weeks apart; half received the vaccine and half got a placebo (a shot of saltwater). Of the 170 cases of COVID-19 that developed in the study participants, 162 were in the placebo group and eight were in the vaccine group. Nine of the 10 severe COVID cases occurred in the placebo group, suggesting that the vaccine reduced risk of both mild and severe COVID.

According to the NEJM article, the vaccine was similarly effective in study participants of different races and ethnicities, body weight categories, presence or absence of coexisting medical conditions, and ages (younger and older than 65). It's worth noting that the FDA felt comfortable authorizing the vaccine for 16- and 17-year-olds, even though the number of teens enrolled in the study was small.

None of the study participants experienced serious side effects. However, most did have pain at the injection site. Also, about half of those receiving the vaccine reported mild to moderate fatigue or headache or both. Chills and fever were also fairly common. Symptoms almost always resolved within 24 to 48 hours.

This vaccine requires two doses, spaced three weeks apart. Although the vaccine appears to provide reasonable protection after the first dose, it provides stronger protection after two doses. We do not yet know how long immunity from this vaccine will last.

The Pfizer/BioNTech vaccine is an mRNA vaccine. The vaccine contains synthetic messenger RNA (mRNA), genetic material that contains instructions for making proteins. Inside the body, the mRNA enters human cells and instructs them to produce a single component of the SARS-CoV-2 virus — the "spike" protein found on the virus's surface. The body recognizes the spike protein as an invader and produces antibodies against it. If the antibodies later encounter the actual virus, they are ready to recognize and destroy it before it causes illness. mRNA vaccines must be stored at very cold temperatures; improperly stored vaccines can become inactive.

Healthcare workers and residents and staff of long-term care facilities will be the first to get the vaccine.

Who will get the first COVID-19 vaccines and who is next?

In mid-December, healthcare workers and residents and staff of long-term care facilities became the first group in the US to start getting the COVID-19 vaccine. The CDC has recommended that adults age 75 years and older and frontline essential workers be vaccinated next. They will be followed by adults aged 65 to 74, people aged 16 to 64 with medical conditions that put them at high risk for severe COVID-19, and remaining essential workers.

State and local authorities are not obligated to follow the CDC's recommendations; they may reprioritize the order in which they distribute the vaccines at their discretion.

There are about 21 million healthcare workers in the US, doing a variety of jobs in hospitals and outpatient clinics, pharmacies, emergency medical services, and public health. Another three million people reside or work in long-term care facilities, which include nursing homes, assisted-living facilities, and residential care facilities. COVID-19 has taken a heavy toll on residents of long-term care facilities. Frontline essential workers are those who cannot work from home and who may not be able to physically distance while working. They include first responders such as firefighters and police, teachers and day care workers, postal workers, and people who work in grocery stores.

The CDC's guidance is based on a recommendation from the Advisory Committee on Immunization Practices (ACIP), made up of experts in vaccinology, immunology, virology, public health, and other related fields. Their work is not limited to the COVID-19 vaccine; they broadly advise the CDC on vaccinations and immunization schedules.

What are adenovirus vaccines? What do we know about adenovirus vaccines that are being developed for COVID-19?

Adenoviruses can cause a variety of illnesses, including the common cold. They are being used in two leading COVID-19 vaccine candidates as capsules (the scientific term is vectors) to deliver the coronavirus spike protein into the body. The spike protein prompts the immune system to produce antibodies against it, preparing the body to attack the SARS-CoV-2 virus if it later infects the body.

In December 2020, AstraZeneca published promising results of an adenovirus-based vaccine that it developed with researchers at the University of Oxford. The study was published in the journal The Lancet.

The Lancet analysis of vaccine efficacy was based on 11,636 adult study participants. Of these, 4,440 participants received a full dose of the coronavirus vaccine, followed four weeks later by another full dose. Nearly 1,400 participants received a half dose of the coronavirus vaccine, followed four weeks later by a full dose. The control group received a meningitis vaccine, followed by a second meningitis vaccine or a placebo (a salt water shot). There were 131 documented cases of COVID-19, all of which occurred at least two weeks after the second shot.

The coronavirus vaccine reduced the risk of COVID-19 by an average of 70.4%, compared to the control group. Surprisingly, the half dose/full dose vaccine combination was more effective, reducing risk of COVID-19 by 90%. The full dose combination reduced risk by 62%. None of the participants who received the coronavirus vaccine developed severe COVID-19 or had to be hospitalized. There was also a reduction in asymptomatic cases.

Most study participants were between the ages of 18 and 55, and white. In addition, the study participants were healthy or had stable underlying medical conditions. More data is needed to understand how effective this vaccine is in people older than 55, people of color, and people with underlying medical conditions. This vaccine is in clinical trials around the world, including the US. But this analysis was based on data from the United Kingdom and Brazil.

The adenovirus used in the AstraZeneca/University of Oxford vaccine is a weakened, harmless form of a chimpanzee common-cold adenovirus. This vaccine can be safely refrigerated for several months.

What are mRNA vaccines and how do they work to help prevent COVID-19?

mRNA, or messenger RNA, is genetic material that contains instructions for making proteins. mRNA vaccines for COVID-19 contain synthetic mRNA. Inside the body, the mRNA enters human cells and instructs them to produce the "spike" protein found on the surface of SARS-CoV-2, the virus that causes COVID-19. The body recognizes the spike protein as an invader, and starts producing antibodies against it. Soon after, the cell breaks down the mRNA into harmless pieces If the antibodies later encounter the actual virus, they are ready to recognize and destroy it before it causes illness.

Two mRNA vaccines, one created by Pfizer and BioNTech and another developed by Moderna, were granted emergency use authorization (EUA) by the FDA in December 2020.

Click here for more new questions and answers.


Symptoms, spread, and other essential information

What is coronavirus and how does it spread? What is COVID-19 and what are the symptoms? How long does coronavirus live on different surfaces? Take a moment to reacquaint yourself with basic information about this virus and the disease it causes.

Click here to read more about COVID-19 symptoms, spread, and other basic information.


Social distancing, hand washing, and other preventive measures

You've gotten the basics down: you're wearing your mask, avoiding crowds, and keeping your distance from friends and family. How do each of these measures help slow the spread of this virus, and is there anything else you can do?

Click here to read more about what you can do to protect yourself and others from coronavirus infection.


COVID-19 vaccines

Based on strong scientific evidence of safety and effectiveness, the FDA authorized the first COVID-19 vaccines less than one year after the first COVID-19 cases were reported. You may be excited, but cautious. You likely still have questions. How do the vaccines work? Who should get them? How long will protection last? Will the vaccine prevent me from infecting others?

Click here to learn more about COVID-19 vaccines.


If you are at higher risk

Though no one is invulnerable, we've seen that older adults are at increased risk for severe illness or death from COVID-19. Underlying conditions, including heart disease, lung disease, and diabetes, increase risk even further in those who are older. In addition, anyone with an underlying medical condition, regardless of their age, faces increased risk of serious illness.

Click here to read more about what you can do if you are at increased risk for serious illness.


If you've been exposed, are sick, or are caring for someone with COVID-19

Despite your best efforts, you may be exposed to coronavirus and become ill with COVID-19. Or you may be in a position where you are caring for a loved one with the disease. It's important to know what to do if you find yourself in any of these situations. Stock up with medications and health supplies now, and learn the steps you can take to avoid infecting others in your household and to avoid getting sick yourself if you are caring for someone who is ill.

Click here to read more about what to do you if you have been exposed, are sick, or are caring for someone with COVID-19.


Treatments for COVID-19: What helps, what doesn't, and what's in the pipeline

Most people who become ill with COVID-19 can recover at home, and there are things you can do to feel better. The FDA has also authorized treatments that doctors may use to treat hospitalized COVID-19 patients, and to treat COVID-19 patients who are not hospitalized but are at risk for becoming severely ill. Researchers around the globe continue working hard to develop other effective treatments.

Click here to read more about measures that can help.


Coronavirus and kids:

So far, the vast majority of coronavirus infections have afflicted adults. And when kids are infected, they tend to have milder disease. Still, as a parent, you can't help but worry about the safety of your children. Many parents are also trying to find a balance between answering their children's questions about the pandemic and enforcing health-promoting behaviors and social distancing rules without creating an atmosphere of anxiety. Not to mention keeping kids engaged and entertained with schools closed and playdates cancelled.

Click here to read more about kids and the coronavirus outbreak.


Coping with coronavirus:

The news about coronavirus and its impact on our day-to-day lives has been unrelenting. There's reason for concern and it makes good sense to take the pandemic seriously. But it's not good for your mind or your body to be on high alert all the time. Doing so will wear you down emotionally and physically.

Click here to read more about coping with coronavirus.


More New Questions and Answers

Can people without symptoms spread the virus to others?

"Without symptoms" can refer to two groups of people: those who eventually do have symptoms (pre-symptomatic) and those who never go on to have symptoms (asymptomatic). During this pandemic, we have seen that people without symptoms can spread the coronavirus infection to others.

A person with COVID-19 may be contagious 48 hours before starting to experience symptoms. In fact, people without symptoms may be more likely to spread the illness, because they are unlikely to be isolating and may not adopt behaviors designed to prevent spread.

But what about people who never go on to develop symptoms? A study published in JAMA Network Open found that almost one out of every four infections may be transmitted by individuals with asymptomatic infections.

This study provides yet another reason to wear face masks and observe physical distancing. Both measures can help reduce the risk that someone who does not have symptoms will infect others.

I am pregnant and plan to eventually breastfeed my baby. Is it safe for me to get a mRNA COVID-19 vaccine?

The CDC, American College of Obstetrics and Gynecology (ACOG), and Society for Maternal-Fetal Medicine agree that the new mRNA COVID-19 vaccines (Pfizer/BioNTech and Moderna) should be offered to pregnant and breastfeeding individuals. But there is a lot we still do not know about the safety of the vaccines in these populations, and your own doctor is in the best position to advise you based on your personal health risks and preferences.

Here are some factors to consider. First, although the actual risk of severe COVID-19 illness and death among pregnant individuals is very low, it is higher when compared to nonpregnant individuals from the same age group. In addition, research suggests that having COVID-19 might increase risk for premature birth, particularly for those with severe illness. Transmission of the virus from mother to baby during pregnancy is possible, but it appears to be a rare event.

mRNA vaccine trials did not deliberately include pregnant individuals, so our knowledge regarding the safety of mRNA COVID-19 vaccines during pregnancy is limited. In animal studies, mRNA vaccines did not affect fertility or cause any problems with pregnancy. mRNA vaccines do not contain any virus, so they cannot cause COVID-19 in a woman or her baby. And our bodies quickly break down and eliminate mRNA particles used in the vaccine, so they are unlikely to reach or cross the placenta. On the other hand, the immunity that a woman generates from vaccination can cross the placenta, and may help to keep the baby safe after birth.

Experts also believe it is most likely safe to get an mRNA COVID-19 vaccine if you're breastfeeding, although breastfeeding people were not included in the vaccine trials. When a person gets vaccinated while breastfeeding, their immune system develops antibodies that protect against COVID-19. These antibodies can be passed through breast milk to the baby and are likely to help protect against infection.

To what extent have younger adults been impacted by COVID-19?

According to a recent article in JAMA, between March and July 2020, there were almost 12,000 excess deaths in people ages 25 to 44. (Excess deaths refers to the gap between actual deaths and the expected number of death based on historical norms.) Though not all of the excess deaths were due to COVID-19, many were.

It's true that younger adults are less likely than older adults to die of COVID-19: Adults in the 25 to 44 age range account for less than 3% of COVID deaths, compared to 80% for people older than 65.

But younger people can get sick enough from the disease to require hospitalization or to die. And they may be among the long haulers — people who continue to experience fatigue, brain fog, shortness of breath, or other symptoms weeks and months after their illness.

And as is true in other age groups, COVID illness and death has a disproportionate impact on younger adults of color.

Because healthy younger adults are at lower risk than other populations, they are likely to be among the last to be vaccinated. That means it is even more important to continue wearing masks, maintaining physical distance, and avoid gathering in groups.

Has a mutation made it easier for the COVID-19 virus to spread?

Like other viruses, the coronavirus responsible for COVID-19 — SARS-CoV-2 — cannot survive without a living cell in which to reproduce. Once it enters human cells, SARS-CoV-2 churns out copies of itself, which go on to infect other cells. Sometimes, a mistake is made when the virus is replicating. This is called a mutation.

Mutations have led to two new coronavirus variants. One, called B.1.1.7, was first detected in the United Kingdom. The other, called B.1.351, originated in South Africa. Both variants have now been detected in countries around the globe.

Both variants contain mutations on the virus's spike protein. Spike proteins on the surface of the SARS-CoV-2 virus bind to and allow the virus to enter human cells. Interestingly, both variants share a key mutation (called N501Y) on the spike protein, that allows the virus to bind more tightly to human cells. This mutation makes the new variants more contagious than previous SARS-CoV-2 variants. But they do not appear to be deadlier than other variants.

The emergence of these highly transmissible variants is yet another reason why mask wearing, physical distancing, and avoiding crowds continues to be as important as ever.

Is there an over-the-counter, at-home test for COVID-19?

The FDA has granted emergency use authorization (EUA) to the first COVID-19 test that can be obtained without a doctor's prescription and fully performed at home. The Ellume COVID-19 Home Test is approved for use in adults and in children age 2 and older, with or without COVID-19 symptoms.

To take the test, you collect a nasal swab, stir it in a vial of processing fluid, then place a drop of the fluid in an analyzer. The device, which detects coronavirus antigens, delivers a positive or negative test result to your smartphone within 20 minutes.

Like other antigen tests, this test is less accurate than "gold standard" PCR tests, but initial studies suggest the accuracy comes close to PCR testing. Until there is much more real-world experience with this home test, the FDA recommends interpreting any result with caution.

If you have COVID-like symptoms, you should self-isolate and contact your doctor whether your test is positive or negative. Your doctor will likely suggest a PCR test for confirmation. You should also self-isolate and call your doctor if you get a positive test result, even if you don't have symptoms. A negative test if you don't have symptoms makes it very unlikely that you are infected. However, you should continue to follow the standard prevention strategies of physical distancing, avoiding crowds, wearing a mask, and hand washing.

This test will be available in drugstores and is expected to cost about $30.

When can I discontinue my self-quarantine?

A full, 14-day quarantine remains the best way to ensure that you don't spread the virus to others after you've been exposed to someone with COVID-19. However, according to CDC guidelines, you may discontinue quarantine after a minimum of 10 days if you do not have any symptoms, or after a minimum of 7 days if you have a negative COVID test within 48 hours of when you plan to end quarantine.

What are monoclonal antibodies? Can they help treat COVID-19?

The FDA has granted emergency use authorization (EUA) to two new treatments for COVID-19. Both are monoclonal antibodies. And both have been approved to treat non-hospitalized adults and children over age 12 with mild to moderate symptoms who have recently tested positive for COVID-19, and who are at risk for developing severe COVID-19 or being hospitalized for it. This includes people over 65, people with obesity, and those with certain chronic medical conditions.

The FDA granted EUA to the first treatment, a monoclonal antibody called bamlanivimab made by Eli Lilly, based on an interim analysis of results from a well-designed but small clinical trial. The study looked at 465 non-hospitalized adults with mild to moderate COVID-19 symptoms who were at high risk of severe disease. A placebo was given to 156 of these patients. The remaining patients were given one of three different doses of bamlanivimab. Patients treated with the monoclonal antibody had a reduced risk (3% versus 10%) of being hospitalized or visiting the ER within 28 days after treatment, compared to patients given a placebo. This is a single-dose treatment that must be given intravenously and within 10 days of developing symptoms.

The FDA has also granted EUA to a combination therapy consisting of two monoclonal antibodies, casirivimab and imdevimab, made by Regeneron. The EUA was based on results from a clinical trial that enrolled 799 non-hospitalized adults with mild to moderate COVID-19 symptoms. The participants were divided into three groups, two of which received the casirivimab-imdevimab combination but at different doses. The third group received a placebo. For patients at high risk for severe disease, those treated with the monoclonal antibody treatment had a reduced risk (3% versus 9%) of being hospitalized or visiting the ER within 28 days of treatment. This treatment must also be given intravenously in a clinic or hospital.

Monoclonal antibodies are manmade versions of the antibodies that our bodies naturally make to fight invaders, such as the SARS-CoV-2 virus. Both of these FDA-approved therapies attack the coronavirus's spike protein, making it more difficult for the virus to attach to and enter human cells.

These treatments are not authorized for hospitalized COVID-19 patients or those receiving oxygen therapy. They have not shown to benefit these patients and could lead to worse outcomes in these patients.


More about COVID-19


Podcast: Thoughts on COVID-19 during this year's flu season (recorded 10/9/2020)

With the COVID-19 pandemic still ongoing, and the annual flu season fast approaching, what can people expect when these two illnesses collide? Are we at greater risk for getting either virus? And could this encounter change how we approach health care now and in the future? Matthew Solan, executive editor of the Harvard Men's Health Watch, talks to Dr. Amy Sherman, an infectious disease expert with Harvard's Brigham and Women's Hospital, about what we may expect when COVID and the flu season meet. To learn more check out our Harvard Medical School Guide, COVID-19, Flu and Colds.

Podcast: Back to school: It's never been more complicated (recorded 7/30/2020)

Sending kids back to school in the fall is always a hopeful time in America. For most families, school is a vital part of the community. With the surge in coronavirus in many areas of the country, getting kids back in the classroom safely will require a major re-evaluation to reduce transmission rates that can impact people of all ages. We talked to Allan Geller, a senior lecturer in the Department of Social and Behavioral Sciences at Harvard's T.H. Chan School of Public Health. Like it or not, for school teachers and administrators, things are going to be different. Don't expect the traditional.


Reliable resources


Terms to know:

aerosols: infectious viral particles that can float or drift around in the air. Aerosols are emitted by a person infected with coronavirus — even one with no symptoms — when they talk, breathe, cough, or sneeze. Another person can breathe in these aerosols and become infected with the virus. Aerosolized coronavirus can remain in the air for up to three hours. A mask can help prevent that spread.

antibodies: proteins made by the immune system to fight infections. If the antibodies later encounter the same infection, they help prevent illness by recognizing the microbe and preventing it from entering cells.

antibody test: also known as a serologic test, an antibody test is a blood test that looks for antibodies created by your immune system. An antibody test can indicate if you were previously infected but is not a reliable way to determine whether you are currently infected.

antigen: a substance displayed on the surface of a microbe that stimulates the body to produce an immune response.

antigen test: a diagnostic test that detects specific proteins on the surface of the virus.

community spread (community transmission): is said to have occurred when people have been infected without any knowledge of contact with someone who has the same infection

contact tracing: a process that begins with identifying everyone a person diagnosed with a given illness (in this case COVID-19) has been in contact with since they became contagious. The contacts are notified that they are at risk, and may include those who share the person's home, as well as people who were in the same place around the same time as the person with COVID-19 — a school, office, restaurant, or doctor's office, for example. Contacts may be quarantined or asked to isolate themselves if they start to experience symptoms, and are more likely to be tested for coronavirus if they begin to experience symptoms.

containment: refers to limiting the spread of an illness. Because no vaccines exist to prevent COVID-19 and no specific therapies exist to treat it, containment is done using public health interventions. These may include identifying and isolating those who are ill, and tracking down anyone they have had contact with and possibly placing them under quarantine.

diagnostic test: indicates whether you are currently infected with COVID-19. A sample is collected using a swab of your nose, your nose and throat, or your saliva. The sample is then checked for the virus's genetic material (PCR test) or for specific viral proteins (antigen test).

effectiveness: indicates the benefit of a vaccine in the real world.

efficacy: indicates the benefit of a vaccine compared to a placebo in the context of a clinical trial.

epidemic: a disease outbreak in a community or region

flattening the curve: refers to the epidemic curve, a statistical chart used to visualize the number of new cases over a given period of time during a disease outbreak. Flattening the curve is shorthand for implementing mitigation strategies to slow things down, so that fewer new cases develop over a longer period of time. This increases the chances that hospitals and other healthcare facilities will be equipped to handle any influx of patients.

false negative: a test result that mistakenly indicates you are not infected when you are.

false positive: a test result that mistakenly indicates you are infected when you are not.

herd immunity: herd immunity occurs when enough people become immune to a disease to make its spread unlikely. As a result, the entire community is protected, even those who are not themselves immune. Herd immunity is usually achieved through vaccination, but it can also occur through natural infection.

immunity: partial or complete protection from a specific infection because a person has either had that infection previously or has been vaccinated against it.

incubation period: the period of time between exposure to an infection and when symptoms begin

isolation: the separation of people with a contagious disease from people who are not sick

long-haulers: people who have not fully recovered from COVID-19 weeks or even months after first experiencing symptoms.

mitigation: refers to steps taken to limit the impact of an illness. Because no vaccines exist to prevent COVID-19 and no specific therapies exist to treat it, mitigation strategies may include frequent and thorough handwashing, not touching your face, staying away from people who are sick, social distancing, avoiding large gatherings, and regularly cleaning frequently touched surfaces and objects at home, in schools, at work, and in other settings.

monoclonal antibodies: laboratory-produced proteins designed to mimic naturally occurring antibodies that target specific antigens on viruses, bacteria, and cancer cells.

mRNA: short for messenger ribonucleic acid, mRNA is genetic material that contains instructions for making proteins.

mRNA vaccines: mRNA vaccines for COVID-19 contain synthetic mRNA. Inside the body, the mRNA enters human cells and instructs them to produce the "spike" protein found on the surface of the COVID-19 virus. The body recognizes the spike protein as an invader, and produces antibodies against it. If the antibodies later encounter the actual virus, they are ready to recognize and destroy it before it causes illness.

pandemic: a disease outbreak affecting large populations or a whole region, country, or continent

physical distancing: also called social distancing, refers to actions taken to stop or slow down the spread of a contagious disease. For an individual, it refers to maintaining enough physical distance (a minimum of six feet) between yourself and another person to reduce the risk of breathing in droplets or aerosols that are produced when an infected person breathes, talks, coughs, or sneezes.

polymerase chain reaction (PCR) test: a diagnostic test that detects the presence of the virus's genetic material.

post-viral syndrome: the constellation of symptoms experienced by COVID-19 long haulers. These symptoms may include fatigue, brain fog, shortness of breath, chills, body ache, headache, joint pain, chest pain, cough, and lingering loss of taste or smell.

presumptive positive test result: a positive test for the virus that causes COVID-19, performed by a local or state health laboratory, is considered "presumptive" until the result is confirmed by the CDC. While awaiting confirmation, people with a presumptive positive test result will be considered to be infected.

quarantine: separates and restricts the movement of people who have a contagious disease, have symptoms that are consistent with the disease, or were exposed to a contagious disease, to see if they become sick

SARS-CoV-2: short for severe acute respiratory syndrome coronavirus 2, SARS-CoV-2 is the official name for the virus responsible for COVID-19.

social distancing: also called physical distancing, refers to actions taken to stop or slow down the spread of a contagious disease. For an individual, it refers to maintaining enough physical distance (a minimum of six feet) between yourself and another person to reduce the risk of breathing in droplets or aerosols that are produced when an infected person breathes, talks, coughs, or sneezes. It is possible to safely maintain social connections while social distancing, through phone calls, video chats, and social media platforms.

spike protein: a protein on the surface of the SARS-CoV-2 virus that binds to and allows the virus to enter human cells.

vector: a harmless capsule. In a vaccine, a vector may be used to deliver a substance into the body in order to prompt an immune response.

virus: a virus is the smallest of infectious microbes, smaller than bacteria or fungi. A virus consists of a small piece of genetic material (DNA or RNA) surrounded by a protein shell. Viruses cannot survive without a living cell in which to reproduce. Once a virus enters a living cell (the host cell) and takes over a cell's inner workings, the cell cannot carry out its normal life-sustaining tasks. The host cell becomes a virus manufacturing plant, making viral parts that then reassemble into whole viruses and go on to infect other cells. Eventually, the host cell dies.

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Harvard Health Publishing Coronavirus Resource Center Experts

The Harvard Health Publishing team would like to acknowledge the Harvard Medical School experts who have contributed their time and expertise: Steven A. Adelman, MD; Ashwini Bapat, MD; Suzanne Bertisch, MD, MPH; Joseph R. Betancourt, MD, MPH; Barry R. Bloom, PhD; Emeric Bojarski, MD; Melissa Brodrick, MEd; Andrew E. Budson, MD; Stephanie Collier, MD, MPH; Todd Ellerin, MD; Huma Farid, MD; Robert Gabbay, MD, PhD, FACP; Alan Geller, MPH, RN; Ellen S. Glazer, LICSW; Ilona T. Goldfarb, MD, MPH; Peter Grinspoon, MD; Abraar Karan, MD, MPH, DTM&H; Sabra L. Katz-Wise, PhD; Alyson Kelley-Hedgepeth, MD; Anthony Komaroff, MD; Douglas Krakower, MD; Debi LaPlante, PhD; Howard E. LeWine, MD; Dara K. Lee Lewis, MD; Sharon Levy, MD, MPH; Kristina Liu, MD, MHS; Julia Marcus, PhD, MPH; Luana Marques, PhD; Claire McCarthy, MD; Chris McDougle, MD; Babar Memon, MD, MSc; Uma Naidoo, MD; Janelle Nassim, MD; Justin Neiman; Vikram Patel, MBBS, PhD; Edward Phillips, MD; Shiv Pillai, PhD, MBBS; John Ross, MD, FIDSA; Lee H. Schwamm, MD; Catherine Ullman Shade, PhD, MEd; Howard J. Shaffer, PhD, CAS; Roger Shapiro, MD, MPH; John Sharp, MD; Robert H. Shmerling, MD; Jacqueline Sperling, PhD; Fatima Cody Stanford, MD, MPH, MPA, FAAP, FACP, FTOS; Monique Tello, MD, MPH; Robyn Thom, MD; Karen Turner, OTR/L; Rochelle Wallensky, MD, MPH; Janice Ware, PhD; Scott Weiner, MD; Sarah Wilkie, MS; Anna R. Wolfson, MD.

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