Evaluation of antibody response in meningococcal patients, contacts and vaccinees in north India.

Serological response was studied in a high risk age 16-30 years group, during the period December 1986-April 1988, following vaccination with a meningococcal vaccine (Biomerieux, France). A total of 200 serum samples were collected from 50 individuals before vaccination and at 1, 3 and 6 months post-vaccination respectively. Antibody response was measured by Enzyme Linked Immuno-Sorbent Assay (ELISA) and indirect haemagglutination assay (IHA). In the vaccinees antibody response by IHA test showed 56%, positivity in the pre-vaccination samples and 82%, 78% and 74% positivity 1 month, 3 months and 6 months in the post-vaccination samples. By ELISA 2%, 80%, 74% and 66% of the above groups showed serological response. Difference in the pre-vaccination and titres/O.D. of various post-vaccination groups was found to be statistically significant (p = 0.001). There was, however, no significant difference (p = 0.05) amongst the titres/O.D. of three post-vaccination groups. Similarly, acute and convalescent blood samples of 25 patients one sample each of 31 contacts was studied for antibody response. In general, higher antibody titres are produced with systemic infection than with local nasopharyngeal infection or following vaccination.