Two-dose varicella vaccinations were more effective and resulted in decreased risk of varicella severity and some disease characteristics than did one-dose varicella vaccinations, in a case-control study of children living in two communities in the United States.
Two doses of the vaccine were 93.6% effective against all clinically diagnosed varicella and 97.9% effective against moderate to severe varicella, compared with children receiving no vaccine, among subjects aged 4 years and older. A single dose of the vaccine was 75.6% effective against all clinically diagnosed varicella and 78.1% effective against moderate or severe disease, compared with no vaccine.
Cases of varicella in patients who had two doses of the vaccine were more likely to involve rashes that resolved in less than 1 week (P = .01) and were less likely to involve vesicular rashes (P = .01), among breakthrough cases in patients aged 4 years and older, reported Dana Perella of the Philadelphia Department of Public Health, and her colleagues. They investigated 125 clinically diagnosed cases of varicella and 408 matched controls from May 2009 through June 2011. The study participants, aged 1-18 years, were residents of West Philadelphia and the Antelope Valley are of Northern Los Angeles.
“With superior protection provided by the two-dose varicella vaccination, compared with the one-dose regimen as demonstrated in our study and others, it will be important to expand school immunization requirements to include two-dose varicella vaccination,” the researchers wrote.
Read the study in Pediatrics (doi: 10.1542/peds.2015-2802).