Health

Coronavirus | Doctors wary of BCG vaccine study

File photo for representation only.

File photo for representation only.  

The vaccine is known to confer a strong immune response that had protective effects beyond just staving off a tuberculosis infection.

Doctors and scientists in India have expressed caution on a study, which argues that countries that have deployed the BCG-tuberculosis vaccine in their immunisation programmes have seen fewer deaths from coronavirus (COVID-19).

The study, that hasn’t been peer-reviewed, but is available for public scrutiny, argues that 55 middle and high-income countries chosen for the analysis, that have a current universal BCG policy had 0.78 deaths per million people, whereas middle and high income countries that never had a universal BCG policy (5 countries) had a larger mortality rate, with 16.39 deaths per million people, a significant variation. Low and middle-income countries, even if they had universal immunisation policies, were excluded from the analysis because they were also likely to have low testing rates for COVID-19 infection and therefore fewer reported deaths. India, while having a universal BCG policy in place and relatively fewer deaths as a proportion of confirmed coronavirus infections, wasn’t included in the analysis. Many experts say that India tests relatively too little.

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The BCG vaccine is known to confer a strong immune response that had protective effects beyond just staving off a tuberculosis infection and because COVID-19 was particularly lethal to the elderly, those countries where the elderly were likely to have had a BCG shot in their childhood were likely to be better protected against coronavirus, the authors argue.

Several studies over the years have shown that the BCG vaccine, because it accentuates a powerful immune response, has conferred a significant degree of protection against leprosy and non-invasive bladder cancers.

Case of Japan

“Italy, where the COVID-19 mortality is very high, never implemented universal BCG vaccination. On the other hand, Japan (and which has a BCG policy since 1947) had one of the early cases of COVID-19 but it has maintained a low mortality rate despite not implementing the most strict forms of social isolation,” Aaron Miller, Mac Josh Reandelar, Kimberly Fasciglione, Violeta Roumenova, Yan Li, and Gonzalo H. Otazu, from the New York Institute of Technology, argue.

Also Iran, which has seen at least 3,000 deaths and has a BCG vaccination policy, only began implementing it in 1984 and therefore anyone over 36 was vulnerable. Japan had 1,655 cases and 65 deaths as of March 29.

Spain, France, the United States, Italy and the Netherlands don’t have universal BCG policies and have seen many deaths from COVID-19. Many of these countries don’t have a universal programme because BCG has been shown to not be always protective against tuberculosis in adults as well as an increased risk of infections from other species of mycobacterium.

 

However it was premature for India — that has had a consistent TB vaccination policy since 1968 — to take comfort from the study.

Gagandeep Kang, microbiologist and executive director, Translational Health Science and Technology Institute, said that only actual data that showed people who’d been immunised and showed less disease would be convincing. For one, it wasn’t known for how long BCG’s protective effect lasted. “Australia, the Netherlands, the United States are going to vaccinate healthcare workers with BCG. So I’d wait for that evidence. There’s also a modified mycobacterium vaccine that’s being tested in Germany. It may well be possible but you have to do more than ‘here’s a map’.”

The authors of study also agree that controlled trials that look at the possible protective effect of the vaccine ought to be done.

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Printable version | Jun 4, 2020 5:53:00 AM | https://www.thehindu.com/sci-tech/health/coronavirus-doctors-wary-of-bcg-vaccine-study/article31234253.ece

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