Peer-reviewed JNU study among 2 that link BCG & Covid again, but some experts not convinced - ThePrint

Bengaluru: Two studies released this week, one led by Indian researchers from JNU, brought back a theory that first emerged in the early days of the pandemic — that BCG vaccination may be linked to reduced Covid-19 transmission and mortality.  .The second study, published in PNAS on 9 July, was carried out by American researchers.The first study involved an assessment of a possible correlation between Covid-19 incidence and mortality with the BCG vaccine, which is primarily targeted at tuberculosis.The American study also found a potential correlation between BCG vaccination rates and Covid mortality, but the authors suggested further research into the subject.The Cell authors classified countries into three groups on the basis of their BCG policy: Countries that never adopted universal BCG vaccination, ones that did but subsequently discontinued it, and ones that currently exercise it. .The authors reportedly found that the number of cases across different age groups was always higher for countries without a BCG policy.The PNAS study, too, noted that countries with no vaccination policy had a higher rate of deaths than those that did.Both studies claim that the case load was marginally lower even in countries with interrupted or irregular BCG drives.The Cell team further speculates that the type of BCG vaccine strain used also plays a role, citing high prevalence despite vaccination in Brazil and Russia.Many countries, including Germany, the Netherlands, Australia, and the US, have initiated trials of BCG vaccines aimed at controlling Covid-19.Immunologist Gobardhan Das, who participated in the Cell study, claims to be working on developing a revamped BCG vaccine for Covid-19.Many observational studies have suggested a link between BCG and Covid-19, but experts in immunology and BCG have called for more research.Ecological studies are observational assessments where existing data is analysed, retrospectively, based on geography, and conclusions drawn from them usually form the basis for further studies.Said Madhukar Pai, epidemiologist at McGill University, Canada, “Several countries now have rapidly escalating Covid-19 outbreaks, including Brazil, India, Russia, Mexico, Peru, Chile.The study authors also noted their own limitations.The Cell study only included data from middle- and high-income countries. .The PNAS study stated that the data is difficult to review because of “broad differences between countries” in socioeconomic status, demographic structure, rural vs urban settings, time of arrival of the pandemic, number of tests and criteria, etc.