BMJ  2005;330:845-846 (9 April), doi:10.1136/bmj.330.7495.845-a

Letter

DTP in low income countries: improved child survival or survival bias?

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

EDITOR—We proposed that BCG and measles vaccine have non-specific beneficial effects, whereas diphtheria-tetanus-pertussis (DTP) vaccination might have no beneficial effect.¹ In response, the World Health Organization commissioned several studies.^2-4 A WHO expert task force found substantial evidence against a deleterious effect of DTP; all studies showed DTP to be associated with reduced mortality. A negative DTP effect was found only in Guinea-Bissau, and this was presumed to be due to a country specific issue or a peculiarity of the data.⁵

In our survival analysis, vaccination status was a time fixed variable, held constant from the initial visit to the next; without perfect information for all children, vaccinations during follow-up could not be accounted for, which means a potential source of bias.¹ In the WHO sponsored analyses, vaccination status was a time varying variable changing status at the date of vaccination, based on information achieved at a subsequent visit.^2-5 . . . [Full text of this article]

HJN@ssi.dk, Bandim Health Project, Danish Epidemiology Science Centre, Statens Serum Institut, DK-2300 Copenhagen S, Denmark

Bandim Health Project, Danish Epidemiology Science Centre, Statens Serum Institut, DK-2300 Copenhagen S, Denmark

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