Invasive pneumococcal diseases in birth cohorts vaccinated with PCV-7 and/or PHiD-CV in the province of Quebec, Canada

Abstract

BackgroundThe 10-valent protein D pneumococcal conjugate vaccine (PHiD-CV) was licensed on the basis of immunogenicity studies and there are no published data on its effectiveness to prevent invasive pneumococcal disease (IPD). In the province of Quebec, Canada, PHiD-CV was introduced in the summer of 2009, replacing the 7-valent CRM197 vaccine (PCV-7). Transition to the new vaccine was recommended regardless of the number of PCV7 doses already administered. MethodsIPD rates in children born in 2007–2010 and observed up to the end of 2010 were computed from laboratory surveillance data. The main vaccine used for the infant primary immunization series (mainly 2 doses at 2–4 months) and the toddler (12 months) booster dose was inferred from the Quebec City Immunization Registry data. ResultsIPD rates were significantly lower in the cohorts exposed to PHiD-CV (35/100,000 person-years) as compared with those exposed to PCV-7 (64/100,000person-years; p=0.03). There was no breakthrough vaccine-type IPD case among children who had received ≥2 PHiD-CV doses for the primary series or a single PHiD-CV dose as a booster. There was also a statistically non-significant lower frequency of 19A and other non-vaccine types IPD cases in children exposed to 2+1 PHiD-CV doses as compared with those exposed to PCV-7. InterpretationResults are compatible with a high level of protection induced by PHiD-CV against IPD caused by homologous serotypes.