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.