Researchers at Yale University have discovered that children are better immunized against chicken pox if they are given two doses of the vaccine.
The results of their study were published in February’s Journal of Infectious Diseases and finds that almost all (98.3 per cent) of the children who were vaccinated a second time between the ages of 4 to 6 did not develop the disease.
In 1995, the American Centers for Disease Control and Prevention (CDC) recommended a single dose of chicken pox vaccine for children ages 1 to 13. Although the infection rate dropped drastically, studies showed the vaccine was only effective on 86 per cent of children.
In 2006, the CDC changed the policy to include a second dose for children ages 4 to 6. Lead author of the study, Dr Eugene Shapiro and his team of researchers found that the second vaccination increased efficiency to 98.3 per cent.
Researchers observed 71 children in Connecticut, aged 4 and older, who had contracted chicken pox. In this group, none had received the two-dose regimen, 66 (93 per cent) had been vaccinated only once, and five (7 per cent) had received no vaccine.
"We weren’t surprised to find that two doses of varicella vaccine are highly effective and are more likely to prevent varicella than a singe dose," said Shapiro. "The findings confirm that, at least in the short term, the policy of routinely administering two rather than one dose of varicella vaccine is sensible. Other countries that are routinely immunizing children with varicella vaccine may consider changing to a two-dose regimen."