Serological diagnosis of mumps: Value of the titration of specific IgG

INTRODUCTION

The aim of this study was to evaluate a cut-off point of the titration of IgG by ELISA in the diagnosis of mumps.

METHODS

A study was made of serum samples from 85 mumps cases (confirmed by PCR in saliva) and 2,351 controls of the general population of the Region of Madrid.

RESULTS

The IgM detection was positive in 21 cases (sensitivity of 24.7%). The best cut-off point corresponded to IgG titres ≥4,900 (sensitivity of 64.7% and specificity of 86.1%). Among 42 patients immunised with at least one dose of measles mumps, rubella vaccine IgM was detected in 4 cases. However, the detection of IgG ≥4,900 was positive in 29 (sensitivity of 69.0%).

CONCLUSIONS

An IgG result of ≥4.900 was almost 5 times more probable in a patient with mumps than in a non-infected patient. The detection of high titres of IgG against mumps could improve the IgM results in vaccinated people.

[An outbreak of mumps in a high school: Estimation of vaccine effectiveness. Zaragoza 2011]

INTRODUCTION

Mumps outbreaks continue to occur, even after the consolidation of vaccination programs. An outbreak of mumps occurred in a high school in Zaragoza during December 2011.

OBJECTIVE

To describe the outbreak and estimate vaccine effectiveness.

METHODS

CASE DEFINITION

unilateral or bilateral swelling of the parotid or other salivary glands for three or more days without any other apparent cause.

REFERENCE POPULATION

People attending the 'Parque Goya' High School or with transmission chain origin in the High School.

OUTBREAK PERIOD

From two days before the onset of symptoms of the first case to five days after the last case. Samples were collected for virus confirmation (IgM, urine culture and oropharyngeal exudate), and isolates were processed for genotyping. A retrospective cohort study was performed in two high school classrooms to estimate vaccine efficacy. Public health authorities conducted active surveillance, isolation of cases, and vaccination of susceptible contacts.

RESULTS

There were 27 cases. Twenty-one (77.8%) were vaccinated with two doses of Measles-Mumps-Rubella vaccine. Twelve (44%) were confirmed microbiologically. G1 genotype was determined in six cases. According to the cohort study, vaccine efficacy for one dose was 34% (95%CI: -44 to 70), and was 67% (95%CI: 28 to 83) for two doses.

CONCLUSIONS

Vaccine effectiveness was lower than expected. Early detection and isolation of cases have been instrumental in preventing new cases in schools.