Study shows BCG revaccination can boost immune efficacy of Covishield

Oct 12,2022

Compared to unvaccinated individuals, BCG revaccinated individuals had significantly better responses to the SARS-CoV-2 spike protein.

A multi-institutional study led by researchers from St. John's Research Institute has found that BCG revaccination of young adults can boost the immune efficacy of Covishield vaccine.
Published last week in Frontiers in Immunology, a peer-reviewed journal, this study provides the first in-depth analysis of immune responses to Covishield, the first and most widely distributed COVID-19 vaccine in India.

BCG vaccine is routinely administered in many countries at birth. When given for the second time in young adults, this group of researchers previously showed that it could boost immune responses targeting genes expressed by Mycobacterium tuberculosis (the causative agent of TB) without any adverse effects.

Historical evidence

There is historical evidence on the beneficial effects of BCG vaccination enhancing immune responses more widely, beyond its known protective effects in preventing TB in the young, including enhancing immune responses specifically induced by a variety of vaccines. This prompted the research team to explore the impact of BCG revaccination of young adults on immune responses induced by the Covishield vaccine as part of the first COVID-19 vaccine roll out programme in India.

Annapurna Vyakarnam, Professor of Microbial Immunology at King’s College, London and Adjunct Professor at St. John’s Research Institute and her research team along with scientists at Christian Medical College, Vellore, Fred Hutchinson Cancer Research Centre, Seattle, USA, Radboud and Leiden University, Netherlands conducted an in depth analysis of Covishield induced immune responses in those revaccinated with BCG and control non-revaccinated subjects over time measuring responses induced by the first dose of Covishield. They were then followed up to 23 weeks post administration of the second dose.

As many as 103 healthcare workers aged 18-24 at St. John’s Medical College Hospital, who had all received BCG vaccine at birth, were recruited for the study from October 2019 to June 2021. Those with chronic illness such as hypertension, diabetes mellitus, heart disease, cancer, kidney/thyroid illness, asthma, epilepsy, jaundice or with a history of clinical tuberculosis disease and on medication were excluded.

“Of the 103, as many as 66 were confirmed Interferon Gamma Release Assay (IGRA) negative (who probably did not have the TB bacteria in their body). While 35 received BCG revaccination and 31 did not prior to getting the COVID jab (Covishield). Compared to unvaccinated individuals, BCG revaccinated individuals had significantly better responses to the SARS-CoV-2 spike protein, including immune response critical for the control of both the Wuhan-Hu-1 and Delta variants of SARS-CoV-2,” Prof. Vyakarnam told The Hindu on Tuesday.

Inherent capacity

“Importantly, our research showed that BCG had the inherent capacity to boost the hosts’ first line of defence, which includes immune cells critical in general for vaccine induced immunity,” she said.

“Our study was designed to test whether immune responses induced by highly efficacious Covishield can be further boosted in a SARS-CoV-2 infection and vaccine naïve population. The fact that BCG does have this potential in a young healthy population calls for further analysis... We highlight the potential of using a cheap and globally available vaccine as an adjuvant for novel and emerging vaccines, an area of significant scientific interest, with the added advantage that the timeline over which BCG adjuvant effects have been noted span several years,” Prof. Vyakarnam said.

“Our findings provide a rational basis for more expanded research on BCG vaccination induced immunity. BCG revaccination of adults can be considered as a low-cost and globally acceptable future pandemic preparedness plan to enhance population immunity to future vaccines targeting current and emerging infectious agents,” she added.