A 42-year-old man, who had taken part in the trial of indigenous coronavirus vaccine Covaxin in Bhopal on December 12, died nine days later, with doctors suspecting that poisoning could be the cause.
The vaccine maker Bharat Biotech said in a statement that preliminary reviews indicated that the death was unrelated to Covaxin.
Dr Rajesh Kapur, Vice Chancellor, People's Medical College and Hospital, a private institute where the trial was conducted, said Deepak Marawi, the deceased, had taken part in the Covaxin trial on December 12.
He died on December 21.
Madhya Pradesh Medico Legal Institute Director Dr Ashok Sharma said the doctor who performed autopsy suspected that Marawi died of poisoning.
However, the exact cause of death would be known from his viscera test, he added.
Bharat Biotech said in a statement that Marawi had fulfilled "all the inclusion and exclusion criteria to be accepted as a participant in the Phase III trial".
He was reported to be healthy in follow-up calls post seven days of his dosing and no adverse reaction was observed or reported, the Hyderabad-based company said.
"The volunteer passed away nine days after the dosing and preliminary reviews indicate that the death is unrelated to the study dosing. We cannot confirm if the volunteer received the study vaccine or a placebo as the study is blinded," it added.
Dr Kapur said that after Marawi's death, the Drug Controller General of India and Bharat Biotech were duly informed.
He said Marawi, a tribal labourer, had volunteered for the trial and was examined.
"All protocols were followed and Marawi's consent was taken before allowing him to participate," he claimed.
Dr Kapur also said he cannot confirm whether Marawi was administered the vaccine shot or a placebo.
"It (the vaccine vial) comes covered and coded. During the trial, 50 per cent people get the actual injection while the rest are given saline," he said.
Kapur said Marawi was kept under observation for 30 minutes after the trial as per guidelines before he was allowed to go. "We monitored his health for 7 to 8 days," he added.
Family members of Marawi claimed that when he returned home, he felt uneasy and experienced some health problems.
"He complained of shoulder pain on December 17. Two days later, he frothed at mouth. He refused to see a doctor saying he would be alright in a day or two. When his condition deteriorated, he was being rushed to hospital when he died midway (on December 21)," they added.
The Drugs Controller General of India last week approved Oxford COVID-19 vaccine Covishield, manufactured by Serum Institute, and Covaxin of Bharat Biotech for restricted emergency use in the country, paving the way for a massive inoculation drive.