Bharat Biotech has said that several studies have been conducted on the safety of its Covid-19 vaccine Covaxin, which has demonstrated an “excellent safety track record”.

The statement came after a study conducted by researchers at Banaras Hindu University showed that nearly one-third of all people who received at least a single shot of Covaxin reported “adverse events of special interest” within a year after vaccination, reported PTI.

An adverse event of special interest, or AESI, 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.

The peer-reviewed study, published in the journal Springer Nature, 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.

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

In a statement to Scroll on Thursday, Bharat Biotech said that for the study to be “effective, informative and to avoid investigator bias”, certain additional data points were required.

The manufacturer said that the “AESI [adverse events of special interest] safety profile of the subjects prior to participation in the study” was needed, along with a “comparison of safety profile of non-vaccinated subjects during the course of the study”.

Bharat Biotech also said that a “comparison of safety profile of subjects who received other vaccines during the course of the study” was also required.

“All study participants should be followed during the course of the study, instead of only a subset,” the manufacturer said.

Findings of the study

According to the study, nearly 50% of the participants 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 the occurrence of Guillain-Barre syndrome, were seen among 1% of the participants, the study claimed. Guillain-Barre syndrome is an autoimmune nervous disorder.

“New-onset skin and subcutaneous disorders, general disorders, and nervous system disorders were the three most common disorders observed in adolescents after receiving the vaccine,” the study said, according to PTI.

Among adults, common adverse events of special interest included musculoskeletal disorders, general disorders and nervous system disorders.

The study also noted that menstrual abnormalities were reported in 4.6% of the female participants, while ocular abnormalities – relating to vision and eyesight – were seen in 2.7% of the participants and hypothyroidism was observed in 0.6% of the cohort.

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.

The fourth death was that of a woman who had suffered multiple episodes of unconsciousness after vaccination, the study said. The cause of her death, and the episodes of unconsciousness, have not been identified and the study noted that “no conclusions could be drawn from these events because of the absence of a definite causality association”.

The researchers recommended extensive surveillance of vaccinated individuals in order to understand the course and outcomes of late-onset adverse events of special interest that the vaccine may still cause.

According to the study, those who received three doses of BBV152 were four times as likely to report adverse events of special interest than those who received two doses.

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 announcement came three months after the pharmaceutical company said in court documents that the Oxford-AstraZeneca vaccine could cause a rare but serious side-effect.

The company admitted in court that the vaccine could lead to thrombosis with thrombocytopenia syndrome – also known by its acronym TTS – which is characterised by blood clotting and low levels of platelets.

The Oxford-AstraZeneca vaccine is sold in India as Covishield and is produced at Pune’s Serum Institute of India.