Effectiveness of booster BCG vaccination in preventing Covid-19 infection.

The evidence that BCG (bacille Calmette-Guerin) vaccine may increase the ability of the immune system to fight off pathogens other than tuberculosis has been studied in the past. This nonspecific immunity gained our interest, especially after initial reports of less cases in countries with universal BCG vaccination. In hopes of possible protective immunity, all staff of the Emirates International Hospital (United Arab Emirates) were offered a booster BCG vaccine in early March 2020. All the hospital staff were then tested for Covid-19 infection by the end of June 2020. We divided the subjects into two groups: booster vaccinated versus unvaccinated. The rate of Covid-19 infection was compared between the groups. Criteria included all staff who were offered the vaccine. Seventy-one subjects received the booster vaccination. This group had zero cases of positive COVID 19 infection. Two hundred nine subjects did not receive the vaccination, with 18 positive PCR confirmed COVID 19 cases. The infection rate in the unvaccinated group was 8.6% versus zero in the booster vaccinated group (Fisher's exact test p-value = .004). Our findings demonstrated the potential effectiveness of the booster BCG vaccine, specifically the booster in preventing Covid-19 infections in an elevated-risk healthcare population.