Before specific covid-19 vaccines were available, many attempts were made to prevent SARS-CoV-2 infections in other ways. This is how one of the most widely used vaccines in the world was used: the tuberculosis vaccine Bacillus Calmette-Guérin (BCG). This vaccine could also protect against other respiratory viruses; We have previously described the immunological mechanisms underlying this (Ned Tijdschr Geneeskd. 2020;164:D5552). The ‘BCG-PRIME study group’ investigated whether elderly people with comorbidities benefit from BCG vaccination in the fight against covid-19 and other respiratory infections (Clin Microbiol Infect. 2023;S1198-743X:00044-7).
The researchers included people over 60 with ≥ 1 comorbidity who had not yet had covid-19 from twenty hospitals. They randomized the participants to BCG vaccination or placebo. The participants then answered questions about their health and healthcare use at regular intervals for six months via an app or by telephone. The researchers obtained relevant additional information from general practitioners and hospital files.
In the period September 7-December 28, 2020, the researchers randomized 6112 patients, who were a median 69 years old. During the follow-up period, the covid-19 vaccination was also started. The groups were comparable in terms of basal characteristics – including in terms of covid-19 vaccination coverage.
There was no difference between the BCG vaccination group and the placebo group in the incidence of SARS-CoV-2 infections (hazard ratio: 1.12; 95% CI: 0.87-1.44) and other respiratory tract infections (hazard ratio: 0.89, 95% CI: 0.63-1.24). The severity and duration of the covid-19 symptoms were also comparable. In addition, there was no significant difference in covid-19-related hospitalization and death. These were only small numbers (respectively 18 vs. 21 admissions and 13 vs. 18 deaths).
Marc Bonten, professor of molecular epidemiology of infectious diseases at UMC Utrecht and one of the BCG-PRIME researchers, draws his conclusions when asked. ‘This study indicates that BCG vaccination does not lead to clinically observable benefits in elderly people with co-morbidities. Other studies show similar results in elderly people in good shape and healthy healthcare workers. In short: there is very consistent evidence that BCG vaccination has no effect on SARS-CoV-2 infections.’
Mihai Netea, also a BCG-PRIME researcher and professor of experimental internal medicine (Radboudumc), believes that the last word has not yet been said about the effect on hospital admission and survival. “But given the current state of the pandemic, it is unlikely that further research will be done in this direction.” A recent experimental study by his hand, among others, indicates that BCG vaccination may have a greater effect on influenza infections.