A tuberculosis vaccine administered during the past 15 years is associated with significantly improved COVID-19 outcomes, especially in young adults, according to a new study.
The researchers from Ben-Gurion University of the Negev (BGU) and The Hebrew University of Jerusalem, analysed the correlation between the Bacille Calmette-Guerin (BCG) vaccine for tuberculosis and COVID-19 outcomes.
The study, published in the journal Vaccines, found that BCG regimes are associated with better COVID-19 outcomes, both in reducing infection rates and death rates per million, especially for people aged 24 or younger who had received the vaccination in the last 15 years.
There was no effect among older adults who had received the BCG vaccine, the researchers said.
Many countries have stopped inoculating their entire population, but some still use BCG widely, they said.
"Our findings suggest exploring BCG vaccine protocols in the context of the current pandemic could be worthwhile," said Nadav Rappoport from BGU.
"A growing number of clinical trials for testing the efficacy of BCG vaccination have been initiated," Rappoport said.
The researchers analysed data from 55 countries with populations of more than three million people, which comprise some 63 per cent of the world's population.
As the pandemic reached different countries at different dates, they aligned countries by the first date at which the country reached a death rate of 0.5 deaths per million or higher.
The researchers controlled for 23 variables including demographic, economic, pandemic-restriction-related, and country health-based.
BCG vaccine administration was shown to be constantly associated with COVID-19 outcomes across the 55 countries, they said.
To ascertain whether other vaccines also influenced COVID-19 outcomes, the team conducted the same analysis for the measles and rubella vaccines and found that those did not have a significant association with COVID-19 outcomes.
Other epidemiological studies have shown the effect of the BCG vaccine beyond tuberculosis, but scientists do not yet know why the vaccine has such an effect.
