New Delhi: While the link between the Bacillus Calmette-Guérin (BCG) vaccination used to fight tuberculosis and a possibly lowered risk of Covid-19 has been debated since the beginning of the pandemic, US researchers revealed that there are several other vaccines that give some degree of protection from the virus.
According to the researchers, including those from the Mayo Clinic, vaccines for Polio, HIB, MMR, Varicella, PCV13, Geriatric Flu and Hepatitis A–Hepatitis B offer a degree of protection from Covid-19.
HIB works against influenza, MMR against measles-rubella, PCV against pneumococcal infections and varicella against chicken pox.
The study, published in Scientific Reports journal, looked at the efficacy of non-Covid vaccines against the SARS-CoV-2 virus and concluded that polio works the best among them.
“In particular, we find that individuals who have been recently vaccinated with one of Polio, HIB, MMR, Varicella, PCV13, Geriatric Flu, or HepA–HepB vaccines have lower rates of SARS-CoV-2 infection,” the researchers wrote.
They added: “These vaccines are promising candidates for follow-up pre-clinical animal studies and clinical trials in the COVID-19. For the rest of the 18 vaccines that we considered, the correlations with SARS-CoV-2 infection were either insignificant or varied across the time horizons of interest,”
Meanwhile, the preliminary findings of the ACTIVATE trial in Canada revealed that there is a 53 per cent decrease in the incidence of all new Covid-19 infections in people with BCG vaccinations.
The double-blind, placebo-controlled study by the University Health Network, Toronto, is looking at whether vaccination with BCG vaccine would reduce participants’ susceptibility to Covid-19.
Polio vaccine the most effective
Apart from Covid vaccines, which have shown efficacies in the range of 62 to 94 per cent, and BCG that is under trial, the researchers found that the polio vaccine provides the best protection.
“At the 1 year and 2 year time horizons, the associations of the Polio vaccine to lower rates of SARS-CoV-2 infection are most robust,” they wrote.
The study further argued that the vaccines probably work by activating broad immune signalling pathways — a non-specific innate immune response that is often referred to as “trained” immunity.
However, once a person contracts the disease, these vaccines do not seem to provide any protection either from the need to get hospitalised or even ICU admission.
In another trial by the Bandim Health Project, a health and demographic surveillance system in the African country Guinea-Bissau, investigators are looking at the effect of the oral polio vaccine in 3,400 people aged above 50 years to test the hypothesis that the vaccine reduces the combined risk of morbidity, hospital admission or death (composite outcome) in Covid-19 by at least 28 per cent over six months.
(Edited by Rachel John)