Department of Health Protection, National Institute for Health and Welfare, P.O. Box 30, FI-00271 Helsinki, Finland. Electronic address: terhi.kilpi@thl.fi.
Pneumococcal conjugate vaccines have potential to prevent significant proportion of childhood pneumonia. Finnish Invasive Pneumococcal disease vaccine trial was designed to assess the vaccine effectiveness (VE) of the 10-valent pneumococcal Haemophilus influenzae protein D conjugate vaccine (PHiD-CV10) against several outcomes. We now report results for pneumonia.
In this nationwide, cluster-randomised, double-blind trial, children younger than 19?months received PHiD-CV10 in 52 clusters or hepatitis vaccines as control in 26 clusters. Infants younger than 7?months at the first vaccination received either 3+1 or 2+1 vaccination schedule, children aged 7-11?months received 2+1, and those 12-18?months of age two-dose schedule. All hospitalizations and outpatient visits to hospital associated with ICD-10 codes compatible with pneumonia were identified through the National Care Register and 1-3 frontal chest X-ray images per event were collected. External readers who were unaware of the patients' vaccination status retrospectively interpreted the images. The evaluated outcomes were hospital-diagnosed, hospital-treated pneumonia as primary diagnosis, and radiologically confirmed pneumonia during the blinded, intention-to-treat follow-up period from the first vaccination to the end of 2011. Total VE was calculated as 1 minus rate ratio of all pneumonia episodes.
47 366 children were enrolled from February 2009, to October 2010. VE against all episodes of hospital-diagnosed pneumonia was 27% (95% confidence interval [CI]: 14%, 38%), 32% (95% CI: 3%, 52%), and 23% (95% CI: -5%, 44%) in subjects enrolled at age