In Belize and in many developing countries we are vaccinated with the BCG vaccine a few days to weeks after birth.1 An interesting observation is being made amidst the COVID-19 pandemic. In these countries, the number of severe cases is comparably low compared to countries that do not administer the BCG vaccine.2
The BCG vaccine was developed to protect against tuberculosis. Interestingly, children that receive the BCG vaccine have an increased immunity to several other bacterial and viral pathogens.3 The BCG vaccine appears to modulate the immune system and provide protection from viral infections in human experimental studies.4 The protective mechanism is not understood and these studies were not conducted with the COVID-19 virus. Therefore, the significance of these finding are unclear4,5
The World Health Organization’s stance is that there is no evidence that the BCG vaccine protects people against infection with COVID-19 virus and that the initial reports are prone to significant bias.5 Nevertheless, given the safety of vaccines, healthcare workers are being vaccinated with BCG as a part of ongoing clinical trials to determine whether these observations will translate to clinically relevant outcomes.6
1. BCG Vaccine (TB vaccine) | Vaccine Knowledge. https://vk.ovg.ox.ac.uk/vk/bcg-vaccine. Accessed April 18, 2020.
2. Shet A, Ray D, Malavige N, Santosham M, Bar-Zeev N. Differential COVID-19-attributable mortality and BCG vaccine use in countries. medRxiv. April 2020:2020.04.01.20049478. doi:10.1101/2020.04.01.20049478
3. Heterologous effects of infant BCG vaccination: potential mechanisms of immunity | Future Microbiology. https://www.futuremedicine.com/doi/10.2217/fmb-2018-0026?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub%3Dwww.ncbi.nlm.nih.gov&. Accessed April 18, 2020.
4. Arts RJW, Moorlag SJCFM, Novakovic B, et al. BCG Vaccination Protects against Experimental Viral Infection in Humans through the Induction of Cytokines Associated with Trained Immunity. Cell Host Microbe. 2018;23(1):89-100.e5. doi:10.1016/j.chom.2017.12.010
5. Bacille Calmette-Guérin (BCG) vaccination and COVID-19. https://www.who.int/news-room/commentaries/detail/bacille-calmette-guérin-(bcg)-vaccination-and-covid-19. Accessed April 18, 2020.
6. BCG Vaccination to Protect Healthcare Workers Against COVID-19 – Full Text View – ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT04327206. Accessed April 18, 2020.