Photo: Reuters

HIGHLIGHTS

• Preprint studies claim fewer Covid-19 cases in countries with BCG
• WHO points to research weaknesses in new scientific brief
• Says no evidence that BCG offers protection from virus

The World Health Organisation (WHO) says it has reviewed three recently published preprint studies claiming a lower number of coronavirus cases in countries having Bacille Calmette-Guérin (BCG) vaccination, and found “no evidence” that BCG offers protection from the virus.

A scientific brief released by the global health body says the three research manuscripts “are prone to significant bias from many confounders, including differences in national demographics and disease burden, testing rates for Covid-19 virus infections, and the stage of the pandemic in each country”.

The WHO says there’s experimental evidence “from both animal and human studies that the BCG vaccine has non-specific effects on the immune system, these effects have not been well-characterised and their clinical relevance is unknown.”

Studies published by different groups of researchers had compared the incidence of Covid-19 cases in countries using the BCG vaccine with countries that don’t, and found that the first category had fewer reported cases.

These preprint studies were published by researchers from various institutions, including the New York Institute of Technology, the Anderson Cancer Center, Texas and the Post Graduate Institute of Medical Education and Research, Chandigarh.

Two controlled clinical trials are still in progress, but “in the absence of evidence”, the WHO says, it “does not recommend BCG vaccination for the prevention of Covid-19”.

But it “continues to recommend neonatal BCG vaccination in countries with a high incidence of tuberculosis”.

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