Salivary antibodies following parenteral immunization of infants with a meningococcal serogroup A and C conjugated vaccine

Bacterial and viral salivary antibody testing is proving sensitive and spec ific, useful for epidemiological studies, and is simple and non-invasive. S alivary serogroup C polysaccharide-specific (SC PS-S) IgA and IgG were dete rmined as a proportion of total salivary IgA and IgG in a group of UK infan ts who were recipients of a conjugated A/C meningococcal PS vaccine. Geomet ric mean concentrations (GMCs) of salivary SC PS-S IgG per mg of total IgG (mu g/mg) were 0.1 pre-vaccination, rising to 8.2 post first, 16.1 post sec ond and 29.3 post third dose of vaccine. For IgA, the corresponding GMCs in ng/mg were 0.1, 82.8, 69.6 and 91.2. Significant correlations (P < 0.0001) were found between serum Ig and salivary IgG SC PS-S antibody for pre-vacc ine and 1 month post each dose of vaccine suggesting that SC PS-S IgG in sa liva was largely derived from serum. Of the five infants whose sera were an alysed for isotype-specific responses, only traces of IgM and IgA were meas urable suggesting that the SC PS-S IgA was locally produced. These findings suggests that the widespread use of meningococcal conjugate vaccines is li kely to reduce nasopharyngeal carriage and may thereby induce herd immunity in the vaccinated population.