Nasal antibody response to mumps virus after vaccination and natural infection.

Nasopharyngeal secretions and sera were collected during an epidemic of mumps in a semi-closed institution. None of the children who received live attenuated mumps vaccine 5 months previously developed any symptoms of mumps. Neutralizing and IgA antibodies against mumps virus were measured by the peroxidase-antiperoxidase method and the fluorescent antibody to membrane antigen method, respectively. The immune responses in nasopharyngeal secretions and serum were studied in four groups (apparently infected, non-apparently infected, non-infected and vaccinated). We found that IgA, which has neutralizing activity, was produced after vaccination as well as after natural infection. It is suggested that local antibody induced by vaccination may contribute to protection against the mumps virus.