Large outbreak of mumps virus genotype G among vaccinated students in Norway, 2015 to 2016

Publié le 20 Septembre 2018
Mis à jour le 5 juillet 2019

From 6 September 2015-May 2016, a large mumps outbreak occurred among vaccinated students in Norway. A case was defined as a person presenting with a clinical mumps infection, notified between 1 September 2015 and 30 June 2016. Confirmed cases had positive laboratory confirmation and probable cases had an epidemiological link; PCR-positive specimens were genotyped. A total of 232 cases were notified (230 confirmed) with median age of 23 years (range 4-81) and 61% were male. Of 68 (30%) confirmed cases that were genotyped, 66 were genotype G and associated with the outbreak. Cases that had received two doses of the measles-mumps-rubella (MMR) vaccine had reduced risk of hospitalisation (adjusted relative risk (aRR): 0.14; 95%CI: 0.03-0.57), mumps-related orchitis (aRR: 0.21; 95% CI: 0.08-0.55) and severe outcome (aRR: 0.25; 95% CI: 0.10-0.62) compared with those unvaccinated. A third dose of the vaccine was offered to approximately 1,300 fully vaccinated close contacts and subsequently reported cases decreased. This large outbreak, occurring among predominately vaccinated students, suggests the current genotype A vaccine offers suboptimal protection against mumps genotype G. We recommend maintaining high vaccination coverage and offering the vaccine to all unvaccinated individuals.

Auteur : Veneti Lamprini, Borgen Katrine, Borge Kaja Sverdrup, Danis Kostas, Greve-Isdahl Margrethe, Konsmo Kirsten, Njølstad Gro, Nordbø Svein Arne, Øystese Kari Stidal, Rykkvin Rikard, Sagvik Eli, Riise Øystein Rolandsen
Eurosurveillance, 2018, vol. 23, n°. 38, p. 1-9