Lower incidence of hospital-treated infections in infants under 3 months of age vaccinated with BCG

Heta Nieminen; Mika Lahdenkari; Ritva K Syrjänen; Hanna Nohynek; Esa Ruokokoski; Arto A Palmu

doi:10.1016/j.vaccine.2022.09.004

Lower incidence of hospital-treated infections in infants under 3 months of age vaccinated with BCG

Vaccine. 2022 Oct 6;40(42):6048-6054. doi: 10.1016/j.vaccine.2022.09.004. Epub 2022 Sep 9.

Authors

Heta Nieminen¹, Mika Lahdenkari², Ritva K Syrjänen³, Hanna Nohynek⁴, Esa Ruokokoski², Arto A Palmu³

Affiliations

¹ Department of Public Health and Welfare, Finnish Institute for Health and Welfare, Tampere, Finland. Electronic address: heta.nieminen@thl.fi.
² Department of Information Services, Finnish Institute for Health and Welfare, Helsinki, Finland.
³ Department of Public Health and Welfare, Finnish Institute for Health and Welfare, Tampere, Finland.
⁴ Department of Health Security, Finnish Institute for Health and Welfare, Helsinki, Finland.

PMID: 36096971
DOI: 10.1016/j.vaccine.2022.09.004

Abstract

Background: Live vaccines potentially have non-specific effects that protect against other infections than those the vaccines are targeted against. The national vaccination program (NVP) in Finland was changed on September 1st, 2006: before BCG vaccine was given to all newborn babies and afterwards to babies in risk groups only. We used this natural experiment to study the non-specific effects of BCG in the frame of NVP using before-after design.

Methods: We compared the incidence of several outcomes obtained from Finnish health registers between children born between July 1st, 2004, and June 30th, 2006 (BCG-eligible) and an age- and season-matched reference cohort born between July 1st, 2007, and June 30th, 2009 (BCG-non-eligible) using Poisson regression. These cohorts were restricted to full-term children whose parents were born in Finland. Follow-up began at birth and lasted 3 months, which is the scheduled age for DTaP-IPV-Hib vaccination, and from 4 months until first birthday. The outcomes included all infections, pneumonia and injuries as a negative control outcome.

Results: The incidence rate ratio (IRR) of the BCG-eligible cohort (N = 93,658) compared to BCG-non-eligible cohort (N = 94,712) for hospital-diagnosed infections was 0.89 (95 %Cl 0.86-0.93) for the 3-month follow-up. The decrease was mainly caused by respiratory infections. In 4-12 months follow-up the BCG-eligible had slightly more infections than BCG-non-eligible children (IRR 1.03, 1.01-1.06).

Conclusions: BCG vaccination was associated with a lower incidence of all hospital-diagnosed infections during the first three months of life. The difference cannot be attributed to lung tuberculosis, since only few paediatric cases occurred in Finland during 2000s. The disappearance of non-specific effect after administration of an inactivated vaccine is compatible with previous studies.

Keywords: BCG; Infections; Non-specific effect; Pneumonia.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

BCG Vaccine*
Child
Cross Infection*
Hospitals
Humans
Immunization Programs
Incidence
Infant
Infant, Newborn
Vaccination

Substances

BCG Vaccine