Case-fatality rate of invasive pneumococcal disease caused by various serotypes-an analysis of nationwide surveillance data from Israel, 2009-2018

Objectives: The 20-valent pneumococcal conjugate vaccine (PCV20) has been introduced in Israel. Its public health benefit depends on its effect on mortality caused by PCV20 serotypes not present in 13-valent pneumococcal conjugate vaccine (PCV13) (PCV20non13). We aimed to describe invasive pneumococcal disease (IPD) characteristics and case-fatality rate (CFR) among adults by serotypes.

Methods: We analysed data from the Israeli nationwide surveillance database of IPD in adults, 2009-2018. The primary outcome was in-hospital CFR within 30 days, focusing on specific serotypes. Adjusted ORs (aORs) for association between PCV20non13 serotypes and mortality were calculated using logistic regression.

Results: Overall, 3864 IPD episodes were reported, 3733 (96.6%) with known serotype, 54% (1705/3123) were in men; 54% (1997/3733) were aged ≥65 years. PCV13-IPD cases constituted 40% of all IPD and decreased during the study years. PCV20non13 and nonPCV20 serotypes constituted 26% and 34% of cases, respectively, and increased over time. The most frequent non-PCV13 serotypes detected were PCV20non13 serotypes 8 (8%), 12F (7.2%), 22F (3%), and nonPCV20 serotype 16F (5%). In-hospital CFR was 22% (698/3140). CFR for PCV13 serotype was 21.1% (265/1255); for PCV20non13, it was 16.2% (124/766); and for nonPCV20, it was 28.5% (289/1014). Among PCV20non13 serotypes compared with PCV13 serotypes, 11A was associated with higher CFR (41%, aOR 3.1, 95% CI: 1.64-5.83), whereas serotype 8 was associated with lower CFR (8%, aOR: 0.5, 95% CI: 0.3-0.8).

Discussion: PCV20non13 serotypes constituted 26% of all adult IPD in the post-PCV13 era. CFR from PCV20non13 serotype IPD was comparable with that from PCV13 serotypes. These data support the potential added benefit of PCV20 in reducing mortality from IPD, though mortality remains substantial from nonPCV20 serotypes. Future IPD-related mortality will depend on the evolution of serotype distribution over time.