OBJECTIVES : Pneumococcal conjugate vaccines (PCVs) have been on the market since the approval of the seven-valent PCV (PCV7) in 2000. PCV7 was subsequently replaced by higher valency vaccines. Higher valency vaccines provide broader serotype coverage against pneumococcal disease, but breakthrough invasive pneumococcal disease (IPD) has been observed [Balsells 2017, Kandasamy 2020] after PCV7 was replaced by PCV13. Furthermore, in clinical trials serotype-specific IgG geometric mean concentrations (GMCs) decreased from PCV7 to PCV13 for shared serotypes, which may contribute to decreased effectiveness observed after the introduction of PCV13 for shared serotypes. Our objective is to predict serotype-specific effectiveness of higher valency PCVs based on IgG concentrations and effectiveness of PCV7.

METHODS : The analysis predicted effectiveness against IPD in UK children for the shared serotypes: 4, 6B, 9V, 14, 18C, 19F, and 23F. First, serotype specific COPs were estimated based on the method of [Siber 2007] using reverse cumulative distribution curves (RCDCs) for IgG levels in placebo- and PCV7-administered subjects and reported serotype-specific PCV7 effectiveness [Andrews 2011]. Then the serotype-specific effectiveness for PCV13 was predicted based on the COPs and the RCDCs for IgG levels in placebo- and PCV13-administered subjects. Predicted serotype-specific COP and PCV13 effectiveness values were compared to those from literature. Similar force of infection and vaccine uptake were assumed.

RESULTS : For each serotype, median and 95% prediction interval of COPs and effectiveness were calculated. Most overlapped with the reported median and 95% confidence intervals of COPs and effectiveness in Andrews et al., 2014 [Andrews 2014].

CONCLUSIONS : These results build upon what was previously published by Siber. We were able to establish serotype-specific COPs and use the COPs to predict serotype-specific vaccine effectiveness for PCV vaccines. The predicted vaccine effectiveness can be used to inform the public health impact of future vaccination strategies using health economic models.