Vaccine Serotypes Continue to Cause Invasive Pneumococcal Disease in the Late PCV Era Especially in Unhoused Adults
Date
2024-11-26
Journal Title
Journal ISSN
Volume Title
Publisher
Canadian Public Health Association
Abstract
Vaccine serotypes continue to cause invasive pneumococcal disease in the post-PCV era especially in unhoused adults
Introduction: PCV7 vaccine was introduced in 2002 to Calgary, and PCV13 was introduced in 2010 in Calgary. Unhoused people account for about 0.2% of the population of Calgary, but 19% of IPD cases from 2000 to 2016.
Methods: The Calgary area Streptococcus pneumoniae research (CASPER) team has been conductin population based surveillance on invasive pneumococcal disease in Calgary, Alberta since 1998. When S. pneumoniae is isolated by culture from a sterile sample, the CASPER team completes a chart review. In addition, antibiotic susceptibility testing, and serotyping through the Quellung reaction are completed by the collaborating laboratory.
Results: Following PCV7 introduction we saw a decline in serotype 4 (ST4). However, after PCV13 was introduced in 2010, ST4 began to increase in prevalence again, primarily in adults. From 2020-2022 unhoused adults accounted for over 30% of all IPD cases despite representing a small proportion of the Calgary population. ST4 represented 42% of IPD cases amongst the unhoused population in 2022, and has been a prevalent serotype in unhoused adults since 2014. The second most prevalent were ST3, ST7F, and ST19A, each accounting for 10% of cases in unhoused adults in 2022. All of these serotypes are included in PCV13 and the newly licenced PCV15 and PCV20. However, ST9V and ST4 are not included in the novel unlicenced V116 vaccine, which includes 9 serotypes that are in PCV20 and 11 unique serotypes.
Conclusions: Serotypes 4, 3, 7F and 9V are the most prevalent serotypes causing disease in Calgary in 2022/2023 in adults despite high levels of vaccination in children. The newly licenced PCV15 and PCV20 vaccines include all these serotypes, but the novel 21-valent V116 vaccine does not. Over 30% of IPD in the last three years was amongst unhoused or provisionally housed people highlighting the importance of reaching this population with vaccines.
Description
Poster presentation, 2024 Canadian Immunization Conference, Ottawa, November 26-28, 2024
Keywords
Streptococcus pneumoniae, Pneumococcus, Serotypes, Pneumococcal conjugate vaccine, Unhoused persons, Homelessness