Association of infant pneumococcal vaccination with pneumococcal pneumonia among mothers: A nested case-control study using the GPRD

Since implementation of infant immunization with 7-valent pneumococcal conjugate vaccine (PCV7), increased rates of pneumococcal pneumonia have been reported among adults. Using a cohort of mother-infant pairs identified from the General Practice Research Database in the UK we found that from 2006 to 2010 the annual incidence rate of pneumococcal pneumonia among mothers increased from 61/100,000 to 81/100,000. We identified 43 cases of pneumococcal pneumonia in mothers and 430 control mother-infant pairs. The conditional odds ratio of pneumococcal pneumonia in mothers whose infants received a three-dose series of PCV7 compared to mothers whose infants received zero, one, or two doses was 4.0(95% confidence interval[95%CI]: 1.0-15.8), and 11.0 (95%CI: 1.2-98.6) when compared with mothers whose infants received no vaccinations. The incidence of pneumococcal pneumonia may have increased in mothers following the introduction of PCV7, possibly because mothers whose infants received PCV7 are at increased risk for pneumococcal pneumonia. Though there is a chance of bias inherent to observational studies, the study findings support close monitoring of adult pneumococcal disease and potential role of adult vaccination needs to be explored. (c) 2013 Elsevier Ltd. All rights reserved.