Mumps serum antibody levels before and after an outbreak to assess infection and immunity in vaccinated students.
BACKGROUND
Since 2009, various mumps outbreaks have occurred in the Netherlands, affecting mostly young adults vaccinated against mumps. In this retrospective study, we estimated attack rates for symptomatic and asymptomatic mumps virus infection based on mumps-specific immunoglobulin (Ig)G concentrations in paired blood samples obtained before and after the mumps outbreaks, collected in 2 university cities. We aimed to identify a serological correlate of immune protection and risk factors for mumps virus infection.


METHODS
Mumps-specific IgG levels were measured by Luminex technology in paired pre- and post-outbreak samples from students from Leiden (n = 135) and Utrecht (n = 619). Persons with a 4-fold increase in mumps IgG concentrations or mumps IgG concentrations >1500 RU/mL were assumed to have had a mumps virus infection.


RESULTS
Attack rates for symptomatic and asymptomatic mumps virus infection were 2.0% and 3.8%, respectively. Pre-outbreak mumps-specific IgG concentrations were lower among cases than among noncases (P = .005) despite vaccination history, but no serological cutoff for immune protection could be established. Mumps among housemates was significantly associated with serological evidence for mumps virus infection (odds ratio, 7.25 [95% confidence interval, 3.20-16.40]; P < .001).


CONCLUSIONS
Symptomatic and asymptomatic mumps virus infections in vaccinated persons can be identified by retrospective assessment of mumps-specific IgG antibodies in blood samples.
Centre for Infectious Disease Control , National Institute for Public Health and the Environment , Bilthoven , The Netherlands ; Department of Viroscience , Erasmus University Medical Centre , Rotterdam , The Netherlands.
Sigrid
S
Gouma
Centre for Infectious Disease Control , National Institute for Public Health and the Environment , Bilthoven , The Netherlands.
Tessa M
TM
Schurink-Van't Klooster
Centre for Infectious Disease Control , National Institute for Public Health and the Environment , Bilthoven , The Netherlands.
Hester E
HE
de Melker
Centre for Infectious Disease Control , National Institute for Public Health and the Environment , Bilthoven , The Netherlands.
Jeroen
J
Kerkhof
Centre for Infectious Disease Control , National Institute for Public Health and the Environment , Bilthoven , The Netherlands.
Gaby P
GP
Smits
Centre for Infectious Disease Control , National Institute for Public Health and the Environment , Bilthoven , The Netherlands.
Susan J M
SJ
Hahné
Centre for Infectious Disease Control , National Institute for Public Health and the Environment , Bilthoven , The Netherlands.
Cécile A C M
CA
van Els
Department of Medical Microbiology , University Medical Centre Utrecht , The Netherlands.
Greet J
GJ
Boland
Department of Medical Microbiology , Leiden University Medical Centre , The Netherlands.
Ann C T M
AC
Vossen
Department of Medical Microbiology and Infection Prevention , Groene Hart Hospital , Gouda , The Netherlands.
Pulak R
PR
Goswami
Centre for Infectious Disease Control , National Institute for Public Health and the Environment , Bilthoven , The Netherlands ; Department of Viroscience , Erasmus University Medical Centre , Rotterdam , The Netherlands.
Marion P G
MP
Koopmans
Centre for Infectious Disease Control , National Institute for Public Health and the Environment , Bilthoven , The Netherlands.
Rob S
RS
van Binnendijk
IgG antibodies; MMR vaccination; asymptomatic infection; attack rates; correlate of protection; mumps virus; risk factors; serology