Studying adults aged 35 and 41 years who have received BCG vaccine and those who have not received it during childhood, Tel Aviv University researchers found no association between BCG vaccination and coronavirus infection in Israel.
A study has found that BCG vaccination during childhood does not have a protective effect against novel coronavirus infection in adulthood. The results were published in the Journal of the American Medical Association (JAMA).
The Israel study gains significance as a study posted in a preprint server medRxiv, which is yet to be peer-reviewed, found an association between countries that have a universal BCG vaccination during childhood and reduced coronavirus cases and even deaths, and higher cases and deaths in countries that did not have a universal BCG vaccination. According to them, BCG vaccination during childhood was conferring protection against coronavirus infection and even deaths in adulthood.
WHO had in a letter published in The Lancet had said randomised controlled trials using the vaccine are needed to understand the safety and efficacy before using it on health-care workers. Even in a Scientific Brief posted on April 12, WHO had said the same: “In the absence of evidence, WHO does not recommend BCG vaccination for the prevention of COVID-19.”
Children born in Israel were routinely administered BCG vaccination as part of national immunisation programme between 1955 and 1982. BCG vaccine coverage during this time was over 90%. Since 1982, only immigrants from countries with high prevalence of tuberculosis have been vaccinated with BCG. This allowed researchers to compare the rate of novel coronavirus infection and instances of severe COVID-19 disease in the two populations with very different BCG vaccination history. Adults aged 35 and 41 years and born three years before and three years after universal BCG vaccination was stopped were included in the study.
Those showing symptoms of novel coronavirus infection tested between March 1 and April 5 were included in the study. Of the 72,060 test results reviewed, 3,064 were from people who were born between 1979 and 1981 and were vaccinated, and 2,869 were born between 1983 and 1985 and were likely not vaccinated with BCG.
No association found
Researchers from Tel Aviv University did not find any statistically significant difference in the proportion of positive test results in the BCG-vaccinated group (361 adults; 11.7%) and the unvaccinated group (299 adults; 10.4%). But the researchers could not conclude any association between BCG vaccination status and severity of disease as there was just one case of severe disease in each group; no deaths were reported in either groups.
“The strengths of this study are the large population-based cohort and the comparison of two similar age groups, thus limiting confounders to a minimum,” they write. They also note that those not born in Israel and therefore with unknown vaccination status are less than 5% in the two groups studied.
Trials using BCG vaccine to test if it protects against coronavirus infection have already begun in 1,000 healthcare workers in the Netherlands, Australia, Germany and U.K. Greece and Texas too have initiated trials. ICMR had planned to carry out a similar trial in India begining end-April.