New immunizations for adults

For many men, vaccinations are kids' stuff. Indeed, most immunizations are designed for children, and most new vaccines are headed for pediatric offices and clinics; the newly approved rotavirus vaccine, which will prevent many cases of childhood diarrhea, is an example. But infections strike people of all ages, and immunizations are important for adults, too.

Aside from travelers and people with special needs and vulnerabilities, healthy adults have had only three vaccines to keep track of: For everyone over 50, a flu shot every fall; for everyone at age 65, a pneumococcal pneumonia shot; and for all of us, a tetanus-diphtheria (Td) booster every 10 years. But two new vaccines have joined the list.

A vaccine for shingles

Doctors know it as zoster, but up to a million Americans are stricken each year by the infection they call shingles. By either name, it's an unsightly, often painful process that can be prevented by a vaccine that was approved in 2006.

The culprit is varicella-zoster virus (VZV), the same virus that causes chickenpox (varicella in children). The vast majority of children recover completely, but that's not the end of the story. Instead of being killed and eliminated from the body, VZV goes into hibernation, hiding out in the part of the nervous system known as the sensory nerve ganglia. In most people, the virus remains dormant and harmless for life, but in up to 15%, VZV becomes active and causes shingles.

Most patients with shingles are older than 60, and some have weakened immune systems. The virus spreads along the sensory nerve to form a line of blisters on one side of the body. Most patients recover fully, but a few develop serious complications, and up to a third develop long-lasting pain (post-herpetic neuralgia). Antiviral medicines, which are often prescribed with steroids, can reduce the risk of pain.

Chickenpox has become rare in American children, thanks to the varicella vaccine that was licensed in 1995. But 90% of American adults had chickenpox as children, and all of them are at risk for shingles.

Enter the new vaccine. It is similar to the pediatric varicella vaccine, but it contains a much larger dose of the weakened VZV virus than the chickenpox vaccine does.

A major 2005 trial in 38,546 adults age 60 and older found the vaccine safe and effective. It reduced the incidence of shingles by more than 51%, and it lowered the risk of persistent pain by more than 66%. The most common side effect was pain at the injection site, which was usually mild.

The new vaccine, Zostavax, is suggested for people age 60 and older but should not be given to those who have immune systems that have been weakened by certain malignancies, therapy with steroids or other immune-suppressing medications, or HIV infection. Zostavax must be kept frozen until it is used, and it is expensive. Doctors don't yet know how long the vaccine's protection will last or if booster shots will be needed.

A booster for whooping cough

Every American infant should get a series of immunizations against tetanus and diphtheria, usually at 2, 4, 6, and 18 months of age, with a booster at about 5 years. But in addition, the childhood vaccine has a third component to protect against pertussis, or whooping cough. For decades that meant a DTP shot; now it's known as DTaP, since the improved whooping cough component is made from an acellular (a) pertussis (P) vaccine.

The adult Td booster lacked a because, unlike tetanus and diphtheria, whooping cough is a childhood illness — or at least it used to be. In recent years, whooping cough has been on the rise. In 1976, there were just 1,010 cases in the United States; in 2004, more than 25,000 cases were reported, with about a quarter appearing in people older than 20 years of age.

Whooping cough is a very serious illness in infants and young children. In adults and adolescents, it's much more subtle. As in youngsters, it often begins with a runny nose and a low-grade fever. Then the cough starts — and typically continues for 2 weeks to 2 months. Most often, the cough is dry, and fever is mild or absent. Adults don't whoop or vomit the way kids do, nor do they get pneumonia. But the cough can be debilitating. It interferes with daily activities and sleep, and it may be violent enough to crack a rib. Most patients recover fully, even without antibiotics, but they can pass the infection to others in the meantime.

Whooping cough is making a comeback because the childhood vaccine's protection wanes over time. Immunity to tetanus and diphtheria also wears off, which is why doctors advise a booster every 10 years. But until now, boosters for adolescents and adults lacked the because older people were likely to develop fever and other reactions. Fortunately, the new acellular pertussis vaccine is much better tolerated, and to be on the safe side, the adult Tdap vaccine actually contains less P than the DTaP given to infants.

Two brands of the new vaccine are available. Boostrix is licensed for use in 10- to 18-year-olds, and Adacel is approved for ages 11–64. Adolescents should get a Tdap booster 5 years after their last Td shot; adults should get it 10 years after their last Td booster. Tdap is not approved during pregnancy or after age 65, but studies are underway to see if it's safe in these circumstances.

As with the Td booster, the Tdap can produce pain and redness at the injection site, and some people develop a low-grade temperature for a day or two. Nobody likes a sore arm — but nobody likes to cough for three or four weeks, either.

More to come

Scientists are working hard to develop vaccines to protect against the expanding number of infections that threaten us; examples range from anthrax to bird flu to HIV. It takes years to bring a vaccine from the lab to FDA approval, but in addition to the vaccines for shingles and whooping cough, the FDA has approved Gardasil, a vaccine that protects women against the strains of human papilloma virus that cause most cases of cancer of the cervix. That makes 2006 a banner year for immunizations. Let's hope the flag of progress will be hoisted again in the years to come.