Dr Ashish Kamat, a co-author of the paper and professor of Urologic Oncology (Surgery) and cancer research at MD Anderson Cancer Center in Houston, Texas.
New Delhi: Countries that do not have a BCG vaccination policy saw ten times greater incidence of and mortality from Covid-19, compared with those who do, a forthcoming study from medical researchers in the US and UK, which analysed data from 178 countries, has found.
BCG, or Bacillus Calmette-Guérin, is a vaccine for tuberculosis and is administered at birth in countries that have historically suffered from the disease, such as India. Many rich nations, such as the US, Italy and Holland, have never had a universal BCG vaccination policy.
The study looked at Covid-19 instances and mortality for 15 days between 9 and 24 March in 178 countries and concluded that “incidence of Covid-19 was 38.4 per million in countries with BCG vaccination compared to 358.4 per million in the absence of such a program. The death rate was 4.28/million in countries with BCG programs compared to 40/million in countries without such a program.” Out of the 178 countries studied, 21 had no vaccination program, while the status was unclear in 26 countries. The latter group was treated as not having a policy for the purpose of this study.
“While we expected to see a protective effect of BCG, the magnitude of the difference (almost 10 fold) in incidence and mortality (of Covid-19) between countries with and without a BCG vaccination program was pleasantly surprising,” said Dr Ashish Kamat, a co-author of the paper and professor of Urologic Oncology (Surgery) and cancer research at MD Anderson Cancer Center in Houston, Texas.
In recent weeks, BCG has emerged as a candidate vaccine for Covid-19, and a 4,000-person clinical trial to test its efficacy against the disease is currently underway in Australia. . But what that means for populations that were inoculated with BCG vaccine in their childhood is not yet clear as SARS-CoV-2 continues to spread around the world, having now infected more than a million people.
“There exists a plethora of evidence from well conducted studies in prestigious peer reviewed journals, as well as through randomized control trials about the effectiveness of BCG vaccine, to confer protective immunity against viral infection,” Dr Kamat said, speaking with ET on the phone from the US.
The question of whether populations that have received BCG vaccination are more resistant to Covid-19 is a critical one as countries put in place lockdowns and economies grind to a halt, hitting people at the economic margins hard, especially in countries such as India. Every day of the ongoing lockdown will cost the Indian economy $4.64 billion, Acuité Research said in a report. But having witnessed the morbid dance of the disease in countries such as Italy, where more than 13,000 people have died, governments are disinclined to take a chance.
“Countries with national program of whole-population BCG vaccination appear to have a lower incidence and death rate from Covid-19. This may be due to the known immunological benefits of BCG vaccination. In the absence of a specific vaccination against Covid-19, population-based BCG vaccination may have a role in reducing the impact of this disease,” says the paper, currently available on ResearchGate, a portal where scientists share studies, and is being reviewed for publication by multiple scientific journals. It’s co-authored by Paul Hegarty and Helen Zafirakis of the Mater Misericordiae University Hospital, Dublin, Ireland and Andrew DiNardo at the Baylor College of Medicine, Houston, Texas.
Dr Kamat says his institution is now also embarking on its own clinical trial by vaccinating healthcare workers. “We are commencing a study in the near future, initially planned for about 1,000 healthcare workers, but with plans to rapidly expand to multiple sites as the demand increases. We will vaccinate healthcare workers at highest risk first, such as those who work in emergency centers, ICUs and watch for how protective the vaccine proves. Clearly the data will be monitored and will be done under the auspices of regulatory bodies including the FDA.” He added that talks are on with institutions in India to take part in the study.
BCG vaccine is used in early stage immunotherapy in bladder cancer and Dr Kamat is a top authority in that field. He is also the president of the International Bladder Cancer Group.
The study says while there might be confounding factors in the correlation, the trend is striking. “We recognize that these data are observational and based on a single time-point and that there may be several confounding issues such as limited testing and reporting in many countries. However as these data are derived from 178 countries, the trend is striking and supports the mechanistic data that exists for BCG as a protective agent not only for viral and other infections but also against cancer.”
But childhood inoculation doesn’t necessarily mean life-long immunity. “But a PPD (purified protein derivative) test can indicate whether or not a person still has BCG-induced immunity or needs to be revaccinated. This could be used to selectively revaccinate high-risk groups or to decide who among the population might be safer against SARS-CoV-2 and could potentially go back into the workforce, for instance,” Dr Kamat said, adding that any policy decision relating to Covid-19 should wait for what the clinical trials say.
Earlier this week, a study from the New York Institute of Technology also noted that countries with a universal vaccination policy, such as Japan and Brazil, seemed to be impacted less by Covid-19 compared with those that did not, such as Italy, US and The Netherlands.
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