Varicella susceptibility and validity of history among U.S. Coast Guard recruits: an outbreak-based study

During a varicella outbreak among U.S. Coast Guard recruits, we examined varicella susceptibility serologically and evaluated validity of disease history. Recruits completed a questionnaire to obtain information on demographics, history of varicella disease, and varicella vaccination. Serological testing for varicella-zoster virus immunoglobulin G antibodies was conducted using an enzyme-linked immunosorbant assay. Among 513 recruits, 21 (4.1%) were seronegative to varicella-zoster virus. Recruits born in Puerto Rico were more likely than recruits born in the U.S. states to be susceptible (prevalence ratio, 4.3; 95% confidence interval, 1.4%, 13.1%). A positive disease history was highly predictive of positive serology (99.1%); however, 73% of those with a negative or uncertain history were also immune. Four (19%) susceptible recruits reported a positive varicella history. Although immunity among recruits was high, varicella outbreaks may occur in closed adult settings due to the high risks of exposure and transmission. Varicella vaccination can prevent these costly, disruptive outbreaks.