BCG vaccine shows promise in boosting immunity, will it work against Covid-19?

The 100-year-old BCG vaccine, used to protect children from tuberculosis, has shown capabilities to boost the immune system in senior citizens in India against Covid-19, a new research from the Indian Council of Medical Research has found.

In fact, early results show that the BCG vaccine is effective in modulating two types of immune responses among the elderly.

BCG vaccine induces enhanced frequencies of memory T and B cells and dendritic cell subsets in elderly individuals. ICMR results have demonstrated that the BCG vaccine has induced enhanced frequencies of central and effector memory CD4+ T cells and diminished frequencies of naïve, transitional memory, stem cell memory CD4+ T cells and regulatory T cells.

BCG vaccination was associated with enhanced innate and adaptive memory cell subsets, as well as total antibody levels among elderly individuals.

This suggests its potential utility against SARS-Cov2 infection by enhancing heterologous immunity.

BCG vaccination also induced enhanced frequencies of immature, classical and activated memory B cells and plasma cells and diminished frequencies of naïve and atypical memory B cells. Finally, BCG vaccination resulted in elevated levels of all antibody isotypes.

This means that initial results are positive. However, while it does give a ray of hope, the study doesn't demonstrate whether immune-boosting actually translates to improved protection against SARS-CoV-2, which would take some time to confirm in the ongoing ICMR trial at six centres, the results of which are expected next year.

Elderly individuals, between 60 and 80 years of age, residing in hotspots for SARS-Cov2 infection were included in the study between July 2020 and September 2020 in Chennai.

Elderly population positive for SARS-Cov2 infection by either antibody (serology) or PCR test; HIV infected or individuals with malignancy or on immunosuppressive drugs or those hypersensitive to vaccinations were not included in the study.

Also, those who were diagnosed with tuberculosis (TB) in the previous 6 months or were currently on anti-TB treatment were not included in the study. 54 participants received a single dose of BCG vaccine (freeze-dried) manufactured by Serum Institute of India (SII).

32 elderly individuals from the same hotspot area were not vaccinated and were considered as controls.