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The total number of coronavirus-related deaths might not have reached triple digits by late March if the United States had mandatory tuberculosis vaccination in place several decades prior, according to a study posted on the website of the University of Michigan (UM) on Monday.
The researchers analyzed daily reports of COVID-19 cases and related deaths in more than 50 countries during a 30-day period, modeling differences between growth curves in countries that have mandated BCG policies at least until very recently, such as Brazil, Ireland, France and India, and countries that do not, say the United States, Italy and Lebanon.
They found countries that have a current policy mandating BCG vaccination, a TB vaccine, have significantly slower growth of both cases and deaths, as compared to all other countries.
Take the United States as an example, the researchers project that the United States would have suffered an estimated 94 deaths, which would have been only 4 percent of the actual death toll of 2,467 in this country on March 29.
The study further observed that vaccination may be seen as a prosocial act. People who are not vaccinated can be protected as long as enough other people are, especially in the United States, which does not mandate BCG.
BCG may be effective when a substantial proportion of the population is made resistant to a virus. That is to say, the spread of the virus may be slowed only when there is "herd immunity" that prevents the virus from spreading easily across the population, said Martha Berg, the study's lead author and a UM psychology graduate student.
The study builds on prior evidence that the BCG vaccination, typically given at birth or during childhood, offers a long-lasting protective effect not only against tuberculosis but also against various other infectious diseases.
The study has some limitations: some countries may have better quality data regarding the number of coronavirus cases and deaths than others; in addition, since BCG is given early in life, it's unclear whether the vaccination might be effective when given to adults nor how long it might provide immunity to COVID-19.
"Moreover, it is uncertain whether BCG might have any adverse effects when given to those already infected with COVID-19," Berg said. "There is an urgent need for randomized clinical trials."
