Non-specific effects of vaccination: Vaccines have non-specific (heterologous) effects

doi:10.1136/bmj.330.7495.844

BMJ 2005;330:844 (9 April), doi:10.1136/bmj.330.7495.844

Letter

Non-specific effects of vaccination

Vaccines have non-specific (heterologous) effects

The first 150 words of the full text of this article appear below.

EDITOR—I support Fine's plea that we review the optimalimmunisation schedule in developing countries using evidencefrom controlled trials rather than observational data.¹ Thereare almost no controlled trials of the effect on mortality fromall causes for any of the vaccines in the World Health Organization'sschedule.

Fine says, incorrectly, that literature does not support non-specificeffects of vaccines.

Firstly, BCG protects against leprosy and is the treatment ofchoice for some types of bladder cancer.²

Secondly, an individual's history of previous infection or immunisationcan clearly influence the response to subsequent infections—immunologistscall this heterologous immunity, rather than non-specific immunity.^3
4

Thirdly, evidence that vaccines have heterologous effects comesfrom controlled trials, and not just observational studies.⁵

It is important to be clear about what is meant by the hypothesisthat vaccines have heterologous (non-specific) effects. Thehypothesis says that in high mortality areas, vaccines may affect. . . [Full text of this article]

Frank Shann, director of intensive care

Intensive Care Unit, Royal Children's Hospital, Parkville, VIC 3052, Australia frank.shann@rch.org.au