Bacterial and viral salivary antibody testing is proving sensitive and specific, useful for
epidemiological studies, and is simple and non-invasive. Salivary serogroup C polysaccharide-specific (SC PS-S) IgA and IgG were determined as a proportion of total salivary IgA and IgG
in a group of UK infants who were recipients of a conjugated A/C meningococcal PS vaccine.
Geometric mean concentrations (GMCs) of salivary SC PS-S IgG per mg of total IgG (μg/mg)
were 0·1 pre-vaccination, rising to 8·2 post first, 16·1 post second 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-vaccine and 1 month post each dose of vaccine suggesting that SC PS-S IgG in saliva was
largely derived from serum. Of the five infants whose sera were analysed for isotype-specific
responses, only traces of IgM and IgA were measurable suggesting that the SC PS-S IgA was
locally produced. These findings suggests that the widespread use of meningococcal conjugate
vaccines is likely to reduce nasopharyngeal carriage and may thereby induce herd immunity in
the vaccinated population.