Monitoring the Effect of Vaccination on Mumps Cases Complications in the Czech Republic - Surveillance Data 2013-2022.

Introduction: Mumps data were analysed to assess the effect of vaccination on mumps complications and hospitalisation.

Methods: The mumps cases reported to the Czech nationwide surveillance system from 2013 to 2022 were analysed using logistic regression with an odds ratio (aOR) adjusted for age, sex, year of onset and administrative region to measure the association between vaccination and complications or hospitalisation. Adjusted vaccine effectiveness (aVE) was calculated: aVE=(1-aOR)x100.

Results: A total of 11,913 mumps cases were reported, of which 6,885 (58%) were male. The median age of the study participants was 16 (range: 0-89 years). No complications occurred in 91% of patients. Mumps orchitis occurred in 633 (9%) male cases. A total of 946 (8%) patients required hospitalisation. The highest proportion of complications and hospitalisations was in the age group 35-44 years. Two doses of vaccine reduced statistically significantly the risk of any complications and of hospitalisation compared with unvaccinated patients: aOR 0.48 (95% CI: 0.37, 0.62), aVE of 52% (95% CI: 38, 63); and aOR 0.43 (95% CI: 0.33, 0.56), aVE of 57% (95% CI: 44, 67), respectively. Two doses showed statistically significant aVE 50% (95% CI: 32, 64) against orchitis, and 59% (95% CI: 23, 79) against meningitis. Among the two-dose recipients, the proportion of complications increased gradually with the time from the second dose.

Conclusions: Our findings demonstrated a protective effect of two-dose vaccination against mumps complications and hospitalisation for mumps. We recommend continuing routine childhood mumps vaccination and maintaining high MMR coverage in Czechia.