Non-specific effects of childhood vaccines

Systematic review.

BCG and Measles vaccine appear to reduce all cause mortality, not just TB and Measles (relative risk 0.7 in trials, 0.5 in observational studies, roughly same for both vaccines).

That’s wonderful, until you see that DTP vaccine appears to increase mortality (in 7 of 9 observational studies).

So are live vaccines “immune boosting” in some general way, whereas inactivated vaccines are not, or actually deleterious?

Large proportion of data from studies in Guinea-Bissau so high risk of bias!

[BMJ 2016; 355]

Systematic review of immunological effects of BCG found evidence of changes in non-specific immunological variables (eg IFN-gamma prodution, enhanced lymphocyte proliferation in response to candida, HBsAg, staph etc) but inconsistent, dubious clinical relevance, and certainly not geographically generalisable.

Ultimately, better designed studies, linked to epidemiology, needed before policy changes can be justified.