Various published studies have suggested that several vaccines routinely administered to infants can have unwanted effects on mortality. This study aims to evaluate and characterize nonspecific immunological effects after the administration of routine childhood vaccines for measles, BCG, pertussis, tetanus, diphtheria, and pertussis.

This was a systematic review and meta-analysis of 77 randomized controlled trials, case-control studies, and cohort studies reporting nonspecific immunological effects after vaccination with standard childhood immunizations. The primary outcomes of the study were possible nonspecific or heterologous immunological effects.

The included studies covered immunizations for the following: BCG, mumps, measles, rubella, pertussis vaccines, diphtheria, and tetanus. BCG was the vaccine intervention in 48% of the studies. In 70% of the cases, the primary outcome measurement was performed between the 1st and 12th month after vaccinations. The researchers reported a total of 143 immunological variables. The findings that compared BCG vaccinated groups with unvaccinated groups suggested a trend towards increased IFN-γ production in vitro in the vaccinated groups. Cohort studies of measures vaccination indicated an increase in lymphoproliferation to microbial antigens from tetanus toxoid and C Albicans.

The research concluded that though some studies indicated consistent nonspecific immunological effects, the quality of evidence was low and could not be considered as the bottom line.

Ref: bmj.com/content/355/bmj.i5225