Gender differences in measles incidence rates in a multi-year, pooled analysis, based on national data from seven high income countries

BACKGROUND: Gender differences in a number of infectious diseases have been reported. The evidence for gender differences in clinical measles incidence rates has been variable and poorly documented over age groups, countries and time periods. METHODS: We obtained data on cases of measles by sex and age group over a period of 11–27 years from seven countries. Male to female incidence rate ratios (IRR) were computed for each year, by country and age group. For each age group, we used meta-analytic methods to combine the IRRs. Meta-regression was conducted to the estimate the effects of age, country, and time period on the IRR. RESULTS: In the age groups < 1, 1–4, 5–9, 10–14, 15–44, and 45–64 the pooled IRRs (with 95% CI) were 1.07 (1.02–1.11), 1.10 (1.07–1.14), 1.03 (1.00–1.05), 1.05 (0.99–1.11), 1.08 (0.95–1.23), and 0.82 (0.74–0.92) respectively. The excess incidence rates (IR) from measles in males up to age 45 are remarkably consistent across countries and time-periods. In the age group 45–64, there is an excess incidence in women. CONCLUSIONS: The consistency of the excess incidence rates in young males suggest that the sex differences are more likely due to physiological and biological differences and not behavioral factors. At older ages, differential exposure can play a part. These findings can provide further keys to the understanding of mechanisms of infection and tailoring vaccination schedules.