COVID-19 vaccines for children and teens: What we do — and don't — know

Editor's note: On August 23, 2021, the FDA granted full approval to the Pfizer/BioNTech COVID-19 vaccine for people ages 16 and older. Children ages 12 to 15 can continue to receive this vaccine under emergency use authorization as more data is collected.

Vaccines have been heralded as a key measure to slow the COVID-19 pandemic and one day bring it to an end. Every day, millions of American adults are receiving one of the authorized vaccines proven highly effective at preventing severe illness that might otherwise lead to hospitalizations and deaths. In the US, most people over 65 have now been fully vaccinated, protecting the most vulnerable in our population.

As an infectious disease specialist, my responses to the questions below are based on what we know so far about infection and vaccines in children and teens. We'll need to continue filling in gaps as research is done and our understanding evolves.

What do we know about how COVID-19 affects children and teens?

Most COVID-19 infections in children are mild or cause no obvious symptoms. However, a small percentage of infected children

• develop a serious inflammatory condition called MIS-C in the two to six weeks following COVID-19 infection. This may happen even in children who have mild symptoms or no symptoms.
• get very sick and need hospitalization or intensive care.

Over 400 children have died from COVID-19 infection. That's greater than the number of childhood deaths during the deadliest flu season in the past two decades.

Vaccinating children to prevent these outcomes is one of the most important reasons driving vaccine studies in children. Further, vaccinating children will be critical to achieving a population-wide level of immunity — herd immunity — sufficient to slow the emergence of dangerous variants and bring an end to the pandemic.

What do we know so far about COVID-19 vaccines in teens?

• The Pfizer/BioNTech vaccine is authorized for use in children and teens ages 12 and older.
• The Moderna and Johnson and Johnson vaccines are authorized for use in people ages 18 and older.
• These authorizations were based on data from participants of these ages in randomized, placebo-controlled trials that demonstrated the safety and efficacy of these vaccines. Efficacy measures how well a vaccine works in the controlled circumstances of a study. Effectiveness is how well a vaccine works outside of a study, when people in the community receive it.

As states expand eligibility for COVID-19 vaccines, children and teens 12 and older can receive the appropriate vaccine through the same sources adults have had access to so far. Available vaccine sites may vary by state and where you receive health care. Check the searchable map on VaccineFinder, or your state board of health.

Vaccine research done so far, or now underway, includes the following:

• Pfizer/BioNTech has completed a trial in 12- to 15-year-olds. This trial used the same dose and schedule of the vaccine as is used in adults: two doses given three weeks apart. The vaccine was safe and well tolerated, elicited strong antibody responses, and had 100% efficacy in preventing mild to severe infection in this age group. The FDA has authorized this vaccine for use in this age group after reviewing the study results. Both the CDC and the American Academy of Pediatrics recommend vaccination for children 12 and older.
• Moderna completed enrolling 12-to 17-year-olds in a similar trial using the same dose and schedule as in adults: two doses given four weeks apart. Data from this trial are expected within the next few months.
• Johnson and Johnson has started a trial of its vaccine for a small number of 16-to 17-year-olds. If the vaccine proves to be safe and effective in that age group, the trial will continue with 12-to 15-year-olds.

What about COVID-19 vaccine trials for younger children?

• Pfizer/BioNTech and Moderna have both begun trials in children 6 months to 11 years old.
• These trials will each begin by testing smaller doses than those given to older children, teens, and adults. This allows researchers to determine which dose is well tolerated and still elicits strong antibody results in younger children.
• Once the dose is set, larger numbers of children in these age ranges will be enrolled in placebo-controlled trials to evaluate the efficacy of these vaccines.

All of these steps will take some time so that they can be done without cutting any corners on safety. The earliest vaccines will likely be available for younger children is late 2021, or perhaps early in 2022.

What is not yet known about COVID-19 vaccines in children and teens

• How long vaccine-induced immunity against COVID-19 infection lasts in children will need to be followed over time. Findings from such studies will help experts decide whether children will need boosters of COVID-19 vaccines in the future.
• Researchers will need to evaluate the impact of these vaccines on protecting children from infection with COVID-19 variants. But biologically, there would be no reason to expect differences in vaccine coverage of variants in adults versus children.