Does BCG protect against coronavirus? New debate over old vaccine

Abantika Ghosh
Explained: New debate over old vaccine

BCG vaccine, started in India as a pilot project in two centres in 1948, went into mass coverage by 1955-56 and remains part of the current Universal Immunisation Programme. (Representational photo/Express Archive)

For millions growing up in India until the 1960s (when the smallpox vaccine came), BCG was the only vaccine — one that literally introduced the concept of vaccines in the country. A limited rollout started in 1948 in a bid to lower the tuberculosis burden, and went on to be expanded across the country.

Does this ages-old BCG vaccine also protect against the novel coronavirus (SARS-CoV2)? That is a question the scientific community worldwide has been discussing over the past few days, ever since a study pending peer review made the claim, and another set of researchers then refuted it. A look at the vaccine, and the arguments in the two studies:

The vaccine, its background

The Bacillus Calmette-Guérin (BCG) vaccine is a live attenuated strain derived from an isolate of Mycobacterium bovis and has been used widely across the world as a vaccine for tuberculosis. A live attenuated vaccine means that it uses a pathogen whose potency as a disease producer has been artificially disabled, but whose essential identifying characters, which help the body mount an immune response to it, have been left unchanged.

India’s tryst with BCG vaccine is also the story of how vaccines entered post-Independence India. In a 2014 article in the Indian Journal of Medical Research on a ‘Brief History of Vaccines and Vaccinations in India’, Dr Chandrakant Lahariya, who is associated with the World Health Organization, wrote: “In May 1948, the Government of India issued a press note stating that tuberculosis was ‘assuming epidemic proportions’ in the country, and that it had ‘after careful consideration’ decided to introduce BCG vaccination on a limited scale and under strict supervision as a measure to control the disease. A BCG Vaccine Laboratory at King Institute, Guindy, Madras (Chennai), Tamil Nadu, was set up in 1948. In August 1948, the first BCG vaccinations were conducted in India. The work on BCG had started in India as a pilot project in two centres in 1948.”

By 1955-56, the mass campaign had covered all states of India. BCG remains part of the basket of vaccines included in the Universal Immunisation Programme.

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Researchers claimed that the BCG vaccine is reported to provide immunity against a large number of respiratory diseases.

COVID-19 link, as claimed

Researchers from the New York Institute of Technology (NYIT) analysed the global spread of COVID-19, correlated it with data from the world BCG Atlas that shows which countries have BCG vaccine coverage, and came to the conclusion that countries with a policy for universal BCG vaccination have had a lower number of cases than those like the US, where universal BCG vaccination was discontinued after the incidence of TB came down, and Italy.

“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. 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. Why did COVID-19 spread in China despite having a universal BCG policy since the 1950s? During the Cultural Revolution (1966-1976), tuberculosis prevention and treatment agencies were disbanded and weakened. We speculate that this could have created a pool of potential hosts that would be affected by and spread COVID-19. Currently, however, the situation in China seems to be improving,” wrote the researchers from the NYIT’s department of biomedical sciences.

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The researchers claimed that the vaccine is reported to provide immunity against a large number of respiratory diseases. They however advocated randomised control trials with the vaccine to see the extent of immunity it can provide against the novel coronavirus, which was not known to the world until December 2019.

“BCG vaccination has been shown to produce broad protection against viral infections and sepsis, 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, we 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 NYIT researchers wrote.

Critique of the claim

Within days of the NYIT study, researchers from the McGill International TB Centre, Montreal wrote out a critique, questioning among other things its methodology, the extent of COVID-19 spread globally at the time the study was conducted, and some of the presumptions made. They questioned the premise that a correlation essentially is one of cause and effect without any other possible explanation.

They wrote: “There is danger in citing that there is evidence that a century-old vaccine may boost immunity in individuals, providing non-specific protection to other illnesses, and by extension protecting against COVID-19 or reducing severity of its presentation based on this analysis alone. Accepting these findings at face value has the potential for complacency in response to the pandemic, particularly in LMICs (low and middle-income countries). One needs only to look at how this has been portrayed in news outlets of several LMICs already; the dangers of such portrayals misinforming the public should not be underestimated, for example, in countries such as India, the wide BCG coverage offered by their universal vaccination policy may create a false sense of security and lead to inaction.”

One of the contentions the McGill researchers make is that by the time the NYIT analysis was done, the spread of COVID-19 had not really happened in the LMICs. It happened later. “For example, COVID-19 cases in India have increased from 195 on March 21 to 1,071 on March 31. In South Africa, cases have increased from 205 on March 21 to 1,326 on March 31,” they noted. India’s cases crossed 2,500 on Friday.

Said Dr K S Reddy, public health expert and president of the Public Health Foundation of India: “Inter-country comparisons of longstanding and uninterrupted national programmes of BCG vaccination suggest a benefit in reducing the severity of the COVID-19 epidemic, in contrast to those who do not have such programmes or started late. There is no direct antiviral effect but BCG could be an immunopotentiator which enables the body to resist the virus better. However, correlation is not proof of causation and we need stronger evidence which may be forthcoming in prevention trials started in some countries.”

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