Does the BCG Vaccine Protect Against COVID-19?
The year 2020 started with the buzz of a new disease in town, now known to everybody as COVID-19. Give or take, the year has been about finding new treatments that work against this virus, refurbishing old drugs and using them as part of treatment protocols, and launching several vaccine trials at full throttle. One idea that gained some momentum was the protective effect of childhood BCG vaccine against COVID-19.
Bacillus Calmette–Guérin (BCG) vaccine is given to newborn children especially in countries with a high burden of tuberculosis (TB). The vaccine protects against the most severe forms of TB with around 70-80% effectiveness.
The thought of using BCG vaccine to reduce impact of COVID-19 stems from the beneficial non-specific effects of the vaccine on the immune system that can protect against respiratory infections. Thus, BCG vaccine might reduce the entry of virus into the bloodstream after SARS-CoV-2 exposure resulting in a less severe disease with faster recovery. Some ecological studies have supported this hypothesis but those have their own limitations, hence, the results can’t be applied far and wide throughout the world.
Photo: BCG vaccine is given to children as a part of routine immunization service.
There are various issues which come in the way of using this vaccine against COVID-19. BCG is given to children primarily and the effects it might have, if given to adults, are unknown. There are adults who have already received the vaccine as children and it is unlikely that a vaccine given several years back will alleviate COVID-19 now. So should people who are already vaccinated, get it again? The researchers are also taking into account the possibility of a more severe disease in some people as a result of boosting the immune system using BCG vaccine. Moreover, there has been a global shortage of this vaccine innumerable times, propelling exposed children into the dark abyss of tuberculosis.
A recent study reviewed a large group of people and compared rates of SARS-CoV-2 in young adult cohorts that were vaccinated or unvaccinated against BCG during childhood. They found a similar rate of positive test results in both groups. Hence, the study did not support the idea of BCG vaccination in childhood protecting against SARS-CoV-2 in adults.
In light of the beneficial non-specific effects of BCG vaccine, clinical trials have begun in Germany and Netherlands. Until we have those results, the World Health Organization (WHO) and Global Alliance for Vaccines and Immunizations (GAVI) recommend that BCG vaccination should only be used for prevention of tuberculosis and not against SARS-CoV-2.
Clinicians and researchers around the world are thinking of all possible ideas to fight SARS-CoV-2 but at the same time it is equally important for science to validate those plausible ideas. In the meantime, we can do our bit by staying at home!
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