100-year-old BCG vaccine given to children may not shield them from Covid-19, says new study
The pandemic has brought a nearly 100-year-old vaccine into the spotlight after a study suggested it could be shielding people from the new coronavirus.
But a new study seems to have dashed these hopes as it found no evidence to support the idea that BCG vaccination during childhood reduces Covid-19 among adults. The team reached these conclusions after comparing infection rates between the vaccinated and unvaccinated populations in Israel.
Some countries administer BCG shots to help children fight tuberculosis (TB), a bacterial disease that affects the lung. However, one study said the vaccine is ineffective against the very disease it was meant to treat.
In the US, doctors generally do not recommend the vaccine for a variety of reasons, including the small risk of infection with the bacteria responsible for TB, its fluctuating effects in preventing adult pulmonary TB.
BCG vaccine made it to the news in late March when a preprint study suggested that countries with universal BCG program had lower coronavirus cases. It provided hopes that the vaccine may offer a protective effect. The idea received further attention when scientists said the BCG could be beneficial against other infectious diseases.
What does the new study say?
The team looked at BCG vaccination data from Israel. Newborns between 1955 and 1982 received a jab under the universal vaccination program. But the country pulled the plug on the initiative soon after.
So the team compared Covid-19 infection rates between individuals born three years before and after the country called off universal BCG program.
The researchers looked at 72, 060 coronavirus test results. Of them, 3,064 -- born between 1979 and 1981 -- may have received the vaccine. The other group, comprising of 2,869 adults born between 1983 and 1985, may have been unvaccinated.
The analysis showed the vaccine did not offer any benefits. About 11.7% of individuals in the first group and 10.4% in the second tested positive. One person developed a severe infection in both groups, and none of them died.
"There was no statistically significant difference in the proportion of positive test results in the BCG-vaccinated group." the authors wrote in their study.
Two clinical trials underway
The earlier study, which suggested that coronavirus rates are lower in countries with universal BCG vaccination, only offers a theory. It is not conclusive.
Such studies are subjected to differences in national demographics, disease burden, testing rates, and the stage of the pandemic in each country, according to the World Health Organization (WHO).
The WHO said, "There is no evidence that the Bacille Calmette-Guérin vaccine (BCG) protects people against infection with the Covid-19 virus."
Currently, two clinical trials -- in Netherlands and Australia-- are evaluating the vaccine against Covid-19. These studies aim to understand whether the vaccine can reduce the disease rate and severity among healthcare workers. "In the absence of evidence, WHO does not recommend BCG vaccination for the prevention of COVID-19. WHO continues to recommend neonatal BCG vaccination in countries or settings with a high incidence of tuberculosis," they added.