[Resurgence of mumps in the vaccine era. Factors involved in an outbreak in Navarre, Spain, 2006-2007].

BACKGROUND AND OBJECTIVE

We analysed a mumps outbreak that occurred in Navarre between August 2006 and December 2007, in which vaccinated persons were widely affected.

PATIENTS AND METHODS

Reports of mumps cases were completed by searching primary, emergency and hospital records and laboratory reports. Factors that could affect the occurrence of cases were analysed by birth cohort.

RESULTS

A total of 2866 mumps cases were detected (attack rate 4.7/1000), with 61% of cases in men and a peak incidence at age 19 (inter-quartile range 16-25 years). 14% of cases were confirmed by laboratory: 59 by virus isolation, 14 by PCR and 333 by IgM. The G1 genotype was identified in 7 cases. 21% of cases had been born before 1980 (pre-vaccine cohorts), and 0.2% had not yet reached the vaccination age (15 months). In the cohorts born between 1980 and 2000 (with the opportunity for vaccination), 94.5% of cases had received at least one dose and 88.3%, two doses. 31% of cases occurred in cohorts vaccinated with a first (1995-1997) or second (1986-1988) dose of the Rubini strain. There was also a record of 772 cases who had received two doses of the Jeryl Lynn strain.

CONCLUSIONS

This widespread outbreak is explained by the concurrence of various factors. The current vaccine has substantially reduced the incidence of mumps, but appears unable to totally eliminate virus circulation.