Table 1.

Main limitations of using serological correlates to evaluate the protection provided by pneumococcal vaccines

Main limitations
Antibody levels are evaluated only one month after completing the priming vaccine doses and not after the booster dose (that is more important for long-lasting protection)
For all the serotypes included in PCVs, the same antibody level is considered protective, although there are data indicating that some serotypes require higher concentrations
Antibody concentrations are influenced by characteristics of the proteins conjugating capsular polysaccharides
Antibody concentrations are only moderately correlated with opsonophagocytic antibody titres
1. Antibody concentrations have limited efficacy in measuring PCVs ability to reduce pneumococcal diseases other than invasive pneumooccal disease

PCVs: pneumococcal conjugate vaccines.