None of the youngsters who came down with the illness had received the two-dose course of the vaccine, while 93 percent had received one dose and 7 percent had not been vaccinated.
In further study, Shapiro's team compared children who received two doses of the vaccine to those who received one dose and found that the effectiveness rates were 98.3 percent and 86 percent, respectively.
In other words, "the odds of developing varicella were 95 percent lower in children who had received two doses of the vaccine compared with those who had received only one," Shapiro said in a news release from the Infectious Diseases Society of America. His team believes the study findings support the CDC's recommendation for the two-dose regimen.
Vaccination for varicella is recommended for everyone who has not had chickenpox, and most states require it before children can enter school or daycare. Older people are more likely to get a severe case because of their weaker immune systems, said Lopez.
"Even if you have had chickenpox in the past, it's safe to get vaccinated again," said Lopez, adding that the vaccine "has a very safe profile."
According to the Pediatrics study, the benefits of even the one-dose vaccination program translated not only into less illness and suffering, but monetary savings as well. During 2009, chickenpox vaccination resulted in savings of more than $1 billion in medical and societal costs, mostly because parents did not need to stay home from work to care for sick children, Lopez said.
According to another expert, the one-dose study points to the social benefits of the vaccination program.
"I think people should feel ve
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