Scientists find correlation between mandatory TB vaccines and fewer coronavirus deaths

  • News Desk, bdnews24.com
    Published: 2020-04-02 16:52:33 BdST

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Countries with mandatory policies to vaccinate against tuberculosis are registering fewer deaths from the coronavirus than countries that don’t have those policies, a new study has found.

The preliminary epidemiological study titled ‘Correlation between universal BCG vaccination policy and reduced morbidity and mortality for COVID-19,’   posted on medRxiv, a site for unpublished medical research, finds a correlation between countries that require citizens to get the bacillus Calmette-Guerin (BCG) vaccine and those showing fewer number of confirmed cases and deaths from Covid-19, reports Bloomberg.

The study showed epidemiological evidence indicating that some of the differences in morbidity and mortality produced by COVID-19 across countries might be partially explained by a country’s BCG vaccination policy.

Italy, where the COVID 19 mortality is very high, never implemented universal BCG vaccination. On the other hand, Japan 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.

Japan has been implementing BCG vaccination since 1947. Gonzalo Otazu, assistant professor at the New York Institute of Technology and lead author of the study, started working on the analysis after noticing the low number of cases in Japan.

China, where the pandemic began, has a BCG vaccine policy but it wasn’t adhered to very well before 1976, Otazu said. Countries including Japan and South Korea, which have managed to control the disease, have universal BCG vaccine policies. Data on confirmed cases from low-income countries was considered not reliable enough to make a strong judgment.

Iran had also been heavily hit by COVID-19 and it started its universal BCG vaccination policy only in 1984 potentially leaving anybody over 36 years old unprotected.

Among high-income countries showing a large number of COVID-19 cases, the US and Italy recommend BCG vaccines but only for people who might be at risk, whereas Germany, Spain, France and the UK used to have BCG vaccine policies but ended them years to decades ago.

BCG vaccination has been shown to produce broad protection against viral infections and sepsis11, raising the possibility that the protective effect of BCG might be not directly related to actions on COVID-19 but on associated co-occurring infections or sepsis.

However, the study also found that BCG vaccination was correlated with a reduction in the number of COVID-19 reported infections in a country suggesting that BCG might confer some protection specifically against COVID-19. The broad use of the BCG vaccine across a population could reduce the number of carriers, and combined with other measures could act to slow down or stop the spread of COVID-19.

Though only a correlation, clinicians in at least six countries are running trials that involve giving frontline health workers and elderly people the BCG vaccine to see whether it can indeed provide some level of protection against the new coronavirus.

CAUTION URGED

Effectiveness of BCG vaccination as a protection against Covid-19 should be researched as any vaccine for the disease is more than a year away from being available, said Eleanor Fish, professor at the University of Toronto’s immunology department. Otazu’s study is yet to undergo review by peers.

“I would read the results of the study with incredible caution,” Fish said.

Otazu is working on a second version of his study that will address some of their concerns.

‘It’s like the BCG vaccine creates bookmarks for the immune system to use later’

A team led by Mihai Netea, an infectious-disease expert at Radboud Universty Medical Centre in the Netherlands, has already enrolled 400 health workers in the trial—200 got the BCG vaccine and 200 received a placebo.

He doesn’t expect to see any results for at least two months. He’s also about to start a separate trial to study the effectiveness of the BCG vaccine on those older than 60. Other trials are taking place in Australia, Denmark, Germany, the UK and the US.