Invasive Streptococcus pneumoniae Infections and Vaccine Failures in Children in Ireland From the Postvaccine Era From 2007 to 2018.

Background: Invasive pneumococcal disease (IPD) causes life-threatening illnesses including meningitis and bloodstream infection. Here, we report the impact of 7- and 13-valent pneumococcal conjugate vaccines (PCV7/PCV13) after introduction into the Irish pediatric immunization schedule in 2008 and 2010, respectively, and the clinical details surrounding suspected PCV vaccine failures.

Methods: Serotyping and antimicrobial susceptibility testing of all culture-confirmed cases referred from children <16 years of age from July 2007 to June 2018 were assessed. Surveillance data were assessed to identify any potential vaccine failures.

Results: The number of IPD cases has decreased by >50% since the introduction of PCVs. The most significant decline PCV serotypes in children <2 years of age, with a 97% decline in PCV7 serotypes, incidence rate ratio (IRR) 0.03, 95% confidence interval (CI): 0.00-0.21; and a 78% decline PCV13-only (PCV13-7) serotypes, IRR 0.22, 95% CI: 0.05-1.04, respectively. However, there has been an increase in non-PCV13 serotypes in children <2 years during the same period (IRR: 2.82, 95% CI: 1.02-7.84; P = 0.0463), with similar serotype trends observed for those 2-4 and 5-15 years of age. There were no clear vaccine replacement serotypes, instead a number of different serotypes emerged. Sixteen vaccine failures were identified, 10 of which were postbooster vaccine failures. Most failures were serotype 19A and resistant to antimicrobials.

Conclusions: Further reducing the incidence of IPD is more challenging as the number of non-PCV13 serotypes has expanded and is now less susceptible to antimicrobials. Consequently, higher valency or broader target vaccines are now required to further prevent IPD in children.