BCG VACCINE: A HYPE OR HOPE AGAINST COVID-19 FLAREUP?

In the race against time, in the middle of death and devastation, many researchers are burning the candles on both ends in discovering an effective vaccine against COVID-19 and some have pinned their hopes on vaccines that already exist, the one that is right under our nose- the BCG vaccine as "The game-changer".

The Bacillus Calmette-Guerin (BCG) vaccine is administered to protect against tuberculosis by inducing an adaptive immune response in the body together with some non-specific effects.  This knowledge has reciprocated to generate the conjecture that this vaccine can also offer protection against Severe Respiratory Syndrome Corona-virus 2 (SARS-CoV-2). BCG-induced innate immunity has shown a reduction of viremia with RNA viruses in experimental human models, reduction of the incidence and severity of respiratory infections, and exertion of other antiviral effects.  Randomized trials in older adults and observational studies in children show that BCG markedly reduces acute respiratory infection. It induces genome-wide epigenetic reprogramming of innate immune cells leading to long-term functional changes and modulation of immunity.

Presently, WHO does not recommend the usage of BCG vaccination to treat COVID-19 because of the absence of any concrete evidence suggesting that the vaccine prevents the SARS-CoV-2 infection? But in contrast to this, there is evidence for the potential biological basis of BCG cross-protection from severe COVID-19. A strong correlation between the BCG index and COVID-19 mortality in different socially similar European countries has indicated that every 10% increase in the BCG index was associated with a 10.4% reduction in COVID-19 mortality. More broadly, countries with current BCG vaccination had lower deaths as compared to countries with lack of, or interrupted, BCG vaccination.

The silver lining is VPM1002, an improved Recombinant BCG with the Mycobacterium bovisurease C gene replaced by the listeriolysin O-encoding gene hly. Compared to the parent vaccine, the advantages of  rBCG vaccine include safety,  more important protective heterologous effects and scalability, which poses VPM1002 to be a promising intervention against SARS-CoV-2.Recent trials have shown that VPM1002 can also be effective against cancer and prevent recurrence of bladder tumours.

Thanks to its broad spectrum of protection and to the prompt availability of the product, showing the efficacy of VPM1002  as  a fundamental step in flattening the curve of the current COVID-19 pandemic and will constitute a strategic advantage for the future: the mechanism of action of VPM1002 is thought to guarantee protection against future viral pandemics or in case of mutations in the current Sars-CoV2 virus, which might impair the efficacy of COVID-19 vaccines currently under development.   

Finding a vaccine or a treatment against the new coronavirus is a race against time, but thankfully a lot of promising projects are already very advanced. Some promising candidates are The University of Oxford and AstraZeneca’s AZD1222 (ChAdOx1nCoV-19), Pfizer and BioNTech’s BNT 162, India’s indigenous Covaxin, etc.

One of the main reasons, why it is essential to stick to WHO's recommendation is that there might be a bare possibility that up-regulation of the immune system by BCG vaccination and its non-specific effects will aggravate COVID-19 in a minority of patients with severe ailments. Two clinical trials addressing this question are underway, and WHO will evaluate the evidence when it is available. As applying “QUICK FIX” and “SHORTCUTS” can lead to disastrous consequences, let’s rely on the results from clinical trials and find whether the BCG vaccine is a hype or hope against COVID-19.

Ms. Elza Baby, 7^th Semester B.Pharm