Comparing serotype coverage of pneumococcal vaccines with PCV21 (V116), a new 21-valent conjugate pneumococcal vaccine, and the epidemiology of its eight unique Streptococcus pneumoniae serotypes (15A, 15C, 16F, 23A, 23B, 24F, 31 and 35B) causing invasive pneumococcal disease in adult patients in Canada: SAVE study, 2018-21

Abstract

Background: V116 is a novel 21-valent pneumococcal conjugate vaccine (PCV) intended for use in adults.

Objectives: To estimate current V116 serotype coverage in adult patients in Canada compared with PCV15, PCV20 and PPSV23 vaccines, and to describe isolate demographics for the eight unique serotypes (15A, 15C, 16F, 23A, 23B, 24F, 31 and 35B) covered by V116.

Methods: From 2018 to 2021 inclusive, the SAVE study collected 5854 invasive pneumococcal disease (IPD) isolates as part of a collaboration between the Canadian Antimicrobial Resistance Alliance and the Public Health Agency of Canada-National Microbiology Laboratory. Serotypes were determined by Quellung reaction and antimicrobial susceptibility testing performed using the CLSI broth microdilution method.

Results: For adult patients (≥18 years), adults 50-64 years and adults ≥65 years, respectively, IPD isolate coverage was PCV15 (42.7%; 41.0%, 39.8%), PCV20 (59.0%; 60.2%, 52.2%), PPSV23 (70.4%; 75.1%, 60.0%), V116 (78.9%; 76.3%, 81.5%) and V116 plus PCV20 (92.2%; 91.0%, 89.3%). The eight unique V116 serotypes accounted for 19.7% and 26.8% of IPD isolates from adults and adults ≥65 years, respectively. Among the eight unique V116 serotypes, 15A and 23A demonstrated the highest rates of MDR (17.0% and 10.2%, respectively); 6.7% of 15A isolates were XDR.

Conclusions: V116 provided significantly (P < 0.05) greater coverage than PCV15, PCV20 and PPSV23 for adults, including older adults, across all Canadian geographic regions, and against IPD isolates with common antimicrobial resistance phenotypes, including MDR. The eight unique V116 serotypes accounted for a higher proportion of IPD isolate serotypes in patients aged ≥65 years than younger adults.

Figure 1.

IPD isolate coverage by vaccine formulation (PCV13, PCV15, PCV20, PPSV23, V116 and V116 combined with PCV20) and proportion of isolates covered by serotypes first introduced or unique to each vaccine formulation (subgroup) for (a) all isolates, (b) isolates from patients aged ≥18 years, and (c) isolates from patients aged ≥65 years.

Figure 2.

Coverage of IPD isolates by V116 unique serotypes stratified by (a) collection year, patient age group, Canadian geographic region and biological sex, and by (b) antimicrobial resistance phenotype. CHL-R, chloramphenicol resistant; CLR-R, clarithromycin resistant; CLI-R, clindamycin resistant; DOX-R, doxycycline resistant; LVX-R, levofloxacin resistant; PEN-R, penicillin resistant; SXT-R, trimethoprim/sulfamethoxazole resistant; any R, any resistance.