Sept. 8, 2000 -- A vaccine against chickenpox is effective for healthy adults, and it's protective over several years, according to a presentation made in New Orleans this week at a meeting of the Infectious Diseases Society of America. The vaccine is now highly recommended for adults who have not contracted chickenpox in the past.
Chickenpox is an infection of the varicella-zoster virus that is usually contracted in childhood and causes a blister-like rash all over the body that lasts for 14 to 17 days. Most people who have had it say it felt like their bodies were covered in mosquito bites. The disease is very contagious: 90% of people who have never had the disease themselves and are exposed to someone with it will catch it.
While chickenpox is usually little more than an itchy annoyance, it does have a serious side. Before the vaccine was available, almost everyone living in the U.S. suffered from the condition by the time they reached adulthood, for an estimated four million cases, 11,000 hospitalizations, and 100 deaths each year. Complications of chickenpox include deep infections at the site of a blister, dehydration, and inflammation of the heart. Encephalitis and meningitis can also occur if the virus infects the brain. These complications are especially more common and severe in older adults.
A vaccine against chickenpox, known as Varivax, was first developed in Japan in 1975, and has been approved for use in the U.S. since 1995. It is a recommended vaccine for all children beginning at age one. Since its approval, monitoring stations set up across the country have determined that Varivax is a safe and effective vaccine for children, reducing the incidence of the disease as well as the risk of complications and need for hospitalization.
What remained to be seen was whether the vaccine worked long-term in adults. The data from this presentation suggest that indeed it does.
The vaccine is highly effective in adults, presenter Krow Ampofo, MD, tells WebMD. "Long-term immunity persists. [Moreover], for those who were unfortunate enough to develop chickenpox [despite vaccination], the disease is milder in terms of the number of [blisters], days sick, and recovery time." Ampofo is a fellow in pediatric infectious diseases at Columbia-Presbyterian Hospital in New York City.
Ampofo and his team studied more than 450 adults who were vaccinated against chickenpox and followed them for more than eight years. Overall, 9% of them developed chickenpox. But only about 20% of those exposed to chickenpox actually contracted the disease. The unlucky few who did come down with the disease suffered a relatively mild attack.
Most importantly, the proportion of vaccinated adults who came down with the disease did not increase over time. Furthermore, for those who developed chickenpox despite vaccination, the severity of symptoms did not worsen as the time since vaccination increased. This indicates that the vaccine maintains its protective power for several years.
Side effects of vaccination did sometimes occur but were mild. They included pain at the site of injection and rash that occurred within six weeks of vaccination.
According to Ampofo, the vaccine, "is highly recommended for susceptible adults. That is, adults who haven't had chickenpox before. If they're not sure whether they've had chickenpox in the past, it's possible for their physician to test [them]."