Chicken pox is caused by the Varicella-zoster virus. It is usually a mild infection, and not life-threatening. Although children with this virus may be miserable for several days, and miss a week of school or day-care (stranding parents at home), they will likely recover from the 250-500 itchy blisters with nothing more to show for it than a few small scars.
Each year about 200,000 of the millions of people around the world who contract chickenpox become seriously ill with complications such as pneumonia or encephalitis (inflammation of the brain). About 2,000 of these people die.
Adults who get chicken pox usually have a much more severe, prolonged case than children. Pneumonia is common.
The rate of hospitalization for chickenpox is almost 900% higher in adults than in children. Adults are more than 20 times more likely to die from this disease.
Pregnant women face the additional fear of serious, even fatal, damage to the baby developing within.
In the past, multiple re-exposures helped to keep people’s immunity high. Since the vaccine is now standard in the United States, the frequency of the natural disease should decline. Those who have had chickenpox as children will not be re-exposed as often, if at all. Their immunity may wane over time, making shingles and adult chickenpox even more common than they are now.
To date, those who have received the vaccine have a much lower incidence of shingles than those who actually had chickenpox over the same time period. Those who receive the vaccine also have a dramatically decreased risk of scarring.
Studies so far have found the chickenpox vaccine to be highly effective in preventing moderate and severe chickenpox in children (Redbook: Report of the Committee on Infectious Diseases, 2009).
For each individual, the vaccine seems quite safe. Reported adverse effects are generally mild — soreness, swelling, rash (at the injection site), fever, tiredness, or fussiness are the most common. The vaccine is not recommended for immunocompromised people, or for pregnant women.
The American Academy Pediatrics currently recommends two doses of the chickenpox vaccine. Typically, the first dose of the vaccine is given at 12 to 15 months of age and the second at 4 to 6 years of age (at school entry). Older children who have not received two doses of the vaccine can receive their catch up shots 28 days apart.