Mumps Outbreaks in Vaccinated Populations: Are Available Mumps Vaccines Effective Enough to Prevent Outbreaks?

Abstract

Increased reports of mumps in vaccinated populations prompted a review of the performance of mumps vaccines. The effectiveness of prior vaccination with 1 dose of vaccine ranged from 72.8% to 91% for the Jeryl Lynn strain, from 54.4% to 93% for the Urabe strain, and from 0% to 33% for the Rubini strain. Vaccine effectiveness after 2 doses of mumps vaccine was reported in 3 outbreaks and ranged from 91% to 94.6%. There was evidence of waning immunity, which is a likely factor in mumps outbreaks, aggravated by possible antigenic differences between the vaccine strain and outbreak strains. Inadequate vaccine coverage or use of the Rubini vaccine strain accounted for the majority of outbreaks reviewed; however, some outbreaks could not be prevented, despite high vaccination coverage with 2 doses of the Jeryl Lynn vaccine strain. Our findings indicate the need for more-effective mumps vaccines and/or for review of current vaccination policies to prevent future outbreaks.

Estimates of Mumps Seroprevalence May Be Influenced by Antibody Specificity and Serologic Method

“…The cutoff points for IgG antibodies to mumps virus, based on index standard ratio (ISR) values, were seronegative, ISR Յ0.90; indeterminate, ISR 0.91 to 1.09; and seropositive, ISR Ն1. 10.…”

“…Mumps outbreaks among two-dose vaccine recipients are not unique to the United States or to the Jeryl Lynn vaccine strain (the only licensed mumps vaccine in the United States). In fact, mumps outbreaks among vaccinated populations have occurred in numerous countries, some of which utilize different strains of vaccine virus (5)(6)(7)(8)(9)(10)(11)(12).…”

“…The observation that naturally acquired wild-type mumps infection does not necessarily confer life-long protection (16,17) suggests that the immune memory to mumps may be inherently unreliable and that breakthrough infection among certain vaccinated individuals could arguably be expected. Furthermore, estimates of mumps vaccine efficacy among two-dose recipients vary, but most are approximately 90% (10,18). The consequences of less-thanoptimal vaccine effectiveness could be compounded by incomplete vaccination coverage, waning immunity, and a lack of asymptomatic natural boosting due to substantially reduced endemic disease.…”

Outbreak-related mumps vaccine effectiveness among a cohort of children and of young adults in Germany 2011

“…8 In randomized controlled trials vaccine efficacy for the monovalent vaccine containing Jeryl Lynn was measured to be 95% and 96%, respectively. 9,10 However, vaccine effectiveness (VE) for this strain determined in outbreak settings ranged from 73% to 91% for 1 dose and was 92% for 2 doses 11 ; a recent Cochrane review found VE for ≥1 dose of Jeryl Lynn containing MMR-vaccines to be 69-81%. Mumps outbreaks in populations with high 2-dose vaccination coverage and among young adults are increasingly reported.…”

“…Several theories have been discussed to explain the age shift and the high proportion of vaccinated cases, such as waning immunity, lack of boosting due to decreased wild virus circulation after vaccine introduction, and mismatch between wild and vaccine virus. 1,11,13,19 In Germany, a seroprevalence study including >13 000 children aged 0-17 y in 2003-06 identified significant waning of immunoglobulin (Ig) G antibodies over this age range 22 ; however, it is still unclear if this observed waning of antibodies also results in a waning protection against mumps disease. Data on the vaccine-induced protection against clinical disease several decades after mumps vaccination are still lacking.…”