The Indian Council of Medical Research on Saturday wrote to the editor of the Drug Safety Journal demanding that the retraction of a study by researchers at Banaras Hindu University highlighting possible safety risks from Bharat Biotech’s Covid-19 vaccine, Covaxin.

The Drug Safety Journal is the official journal of the International Society of Pharmacovigilance.

The study claimed that nearly one-third of all persons who received at least one shot of Covaxin reported “adverse events of special interest” within a year after vaccination.

The study came days after pharmaceutical company AstraZeneca announced that it is withdrawing its vaccine against Covid-19 globally due to a “surplus of available updated vaccines”.

The peer-reviewed study, published in the Springer Nature journal, was conducted between January 2022 and August 2023 with 926 participants – 635 adolescents and 291 adults – who received the BBV152 vaccine. BBV152 is the development name for Covaxin.

In his letter to the journal’s editor, Indian Council of Medical Research Director General Dr Rajiv Bahl wrote: “ICMR cannot be associated with this poorly designed study which purports to present a ‘safety analysis’ of Covaxin due to…critical flaws.”

Bahl wrote that the study had not compared the prevalence of such adverse events between the vaccinated group and a corresponding group of unvaccinated individuals, known as a control group.

“The reported events in the study cannot be linked or attributed to Covid-19 vaccination,” Bahl wrote. “The study does not even provide background rates of observed events in the population, making it impossible to assess the change in incidence of observed events in the post-vaccination period.”

Bahl also accused the study’s authors of other alleged lapses in methodology. The respondents were contacted only via telephone and had not been physically examined, Bahl pointed out, adding that “the method of data collection has a high risk of bias”.

The letter continued: “We therefore ask you to immediately remove the acknowledgement to ICMR and publish an erratum. We request you to retract this paper which implicitly makes conclusions about vaccine safety that are not supported by evidence.”

“We have also noticed that you have similarly acknowledged ICMR in similar previous papers without permission,” Bahl added in his letter. “Please explain why ICMR should not seek legal and administrative action against you.”

Bahl wrote an identical letter to the study’s authors, Dr Upinder Kaur and Dr Sankha Shubhra Chakrabarti.

While Kaur is an assistant professor in the department of pharmacology at the Institute of Medical Sciences, Banaras Hindu University, Chakrabarti heads the institute’s geriatric medicine department.

The participants of the study were interviewed about adverse events of special interest that they may have experienced within a year of getting vaccinated against Covid-19. They were asked questions about events distinct from more routine adverse events, including fever and soreness.

An adverse event of special interest is a pre-specified and medically significant event that, in this case, may be associated with the vaccine. Such events are supposed to be carefully monitored and require further study to establish their causality.

Nearly 50% of them reported infections within a year of being administered Covaxin, with a majority reporting viral upper respiratory tract infections. Serious adverse events of special interest, like strokes and Guillain-Barre syndrome, were seen in 1% of the participants. Guillain-Barre syndrome is an autoimmune nervous disorder.

Four deaths were also reported in the study sample. Stroke was the main reason in two of the deaths. One of the deaths was caused by post-Covid-19 rhinocerebral mucormycosis, a rare fungal infection of the sinuses and brain, which was contracted after vaccination, the patient’s caregivers alleged.

In a statement to Scroll on Thursday, Bharat Biotech said that several previous studies had demonstrated an “excellent safety track record” of the Covaxin vaccine. For the Banaras Hindu University study to be “effective, informative and to avoid investigator bias”, certain additional data points were required, the manufacturer claimed.

The Banaras Hindu University said on Monday that it has taken note of the “series of reactions” to the study and that its Institute of Medical Sciences was looking into the matter.

“The individuals have communicated their responses to the ICMR,” the university said in a press statement. “Additionally, the Institute of Medical Sciences is also working on further strengthening and improving its research ecosystem.”