Impact of the MMR vaccine on the incidence of mumps in the Community of Madrid and evaluation of the effectiveness of the Jeryl-Lynn strain. Years 1998–2016

Abstract Introduction Mumps is characterized by parotid inflammation and fever and is preventable by vaccination with MMR vaccine. The objective of the study is to assess the impact and effectiveness of the vaccine. Material and methods Cases notified to the Notifiable Disease System between 1998 and 2016 were used for the study. The vaccine effectiveness (VE) was calculated in cohorts vaccinated with two doses of Jeryl-Lynn, and the impact was calculated by comparing incidences by age and by Rubini (1995–1998) and Jeryl-Lynn (1999–2002) cohorts during the periods 1998–2004, 2005–2009 and 2010–2015. The incidences for age group and period were compared with the previous period and the incidences for cohorts were compared within a period with incidence ratios (IR) using Poisson models. The VE was estimated using the screening method using logistic regression models. Results 13,816 cases were reported. The incidence in 2005–2009 was higher than in 1998–2004 (IR: 1.46, 95% C I: 1.40–1.53), and it remained stable in 2010–2015 (IR: 0.99, 95% CI: 0.95–1.03). The average incidence rate of the Rubini cohort was 69.43 and the Jeryl-Lynn cohort was 32.24. The IR was 0.25 (95% CI: 0.22–0.29), 0.55 (95% CI: 0.49–0.61) and 0.88 (95% CI: 0.76–1.00) for each period respectively. 2574 cases were included in the VE study. EV decreased over time reaching not significant values after seven years of follow-up (VE: 55%, 95% CI: 82 to −12%). Conclusions Parotiditis behavior is characterized by fluctuations, changes in presentation and a decrease in VE.