Measles vaccination during the respiratory virus season and risk of vaccine failure.

OBJECTIVE

To determine whether measles vaccine failure is more common in persons who were vaccinated during the respiratory virus season, when they were more likely to have had concurrent minor illnesses.

DESIGN

Population-based case series and case-control study.

SETTING

Wisconsin and Ohio.

SUBJECTS: The case series included all 545 of the states' residents who had confirmed measles reported during 1985 through 1990 and a history of receiving a single dose of measles vaccine during 1975 through 1988 at 15 to 59 months of age. In a case-control study restricted to 1984 through 1988 vaccinees, season of vaccination was compared in 170 case children and 6070 control students.

MAIN OUTCOME MEASURE: Risk of clinical vaccine failure after measles vaccination during the respiratory virus season (September through May) or the peak season (November through March) compared with summertime (June through August), after adjustment for age at vaccination and place of residence.

RESULTS

In the case series of persons with vaccine failure, the proportion who had been vaccinated during the respiratory virus season (74.7%) was no greater than expected (September through May = 74.8% of the year). In the case-control study, vaccination during the respiratory virus season (odds ratio, 0.92; 95% confidence interval, 0.66 to 1.30) or the peak season (odds ratio, 0.93) did not increase the risk of vaccine failure.

CONCLUSION

Despite the high and strongly seasonal prevalence of viral respiratory illness in young children, routine childhood measles vaccination during the respiratory virus season does not increase their risk of vaccine failure. Findings provide epidemiologic support for recently strengthened recommendations that measles vaccination not be deferred in children with minor respiratory illnesses.