No link between sudden deaths & Covid vaccination, says ICMR study. Family history, lifestyle factors

New Delhi: A critical study conducted by the Indian Council of Medical Research (ICMR) to investigate the correlation between Covid-19 vaccination and the cases of sudden cardiac arrests in the country, reported over the past few years, has ruled out any link between immunisation and the deaths.

“Covid-19 vaccination did not increase the risk of unexplained sudden death among young adults in India,” the study published in the Indian Journal of Medical Research Tuesday said. “Two doses of the vaccine lowered the odds of unexplained sudden death whereas a single dose did not,” it added.

It also said that past Covid-19 hospitalisation, family history of sudden death and certain lifestyle behaviours increased the likelihood of unexplained sudden death.

The country’s apex health research agency had been tasked with making the assessment whether such deaths among India’s seemingly healthy young adults were linked to Covid infection or vaccination.

The study was conducted through the participation of 47 tertiary care hospitals across India and the cases looked at — a total of 729 — were apparently healthy individuals aged 18-45 years, without any known comorbidities. They had died suddenly of unexplained causes between October 2021 and March 2023.

The cases could have been a ‘witnessed’ death, wherein death occurred in a hospital within 24 hours of hospitalisation; or an ‘unwitnessed’ death, wherein death of a person considered previously healthy, occurred outside hospital setting within 24 hours. This second category includes persons brought dead to the hospital.

They were compared with 2,916 control cases of similar age groups in the neighbourhood, and their Covid-19 and vaccination backgrounds, habits and lifestyle were studied.

“Our findings did not indicate any evidence of positive association of unexplained sudden death with Covid-19 vaccination,” the researchers noted.

However, a history of sudden death in the family, Covid-19 hospitalisation and certain high risk behavioural factors were positively associated with unexplained sudden death among young Indians, they said.

“We found no evidence of a positive association of Covid-19 vaccination with unexplained sudden death among adults. On the contrary, the present study documents that COVID-19 vaccination indeed reduced the risk of unexplained sudden death in this age group,” it said.

Dr Tarun Bhatnagar, a co-author of the paper and a scientist associated with the ICMR-National Institute of Epidemiology, told ThePrint that the analysis has highlighted that the usual risk factors, such as use of alcohol and tobacco, family history of sudden cardiac arrests and unaccustomed vigorous physical activity are the biggest culprits behind the number of unexplained deaths.

“These risk factors always operate even without the Covid-19 background but in those with a history of infection, particularly in those with severe infection, the risk seems to have been aggravated,” he said.

Globally, the incidence of sudden death among young adults has been estimated to be about 0.8-6.2 per 100,000 every year, the study said.

Cardiovascular causes — including arrhythmia, myocardial ischaemia, cardiomyopathy, myocarditis, aortic aneurysm and valvular diseases — are the most commonly reported causes of such deaths.

Cardiologist Dr K. Srinath Reddy, who has been a member of India’s Covid-19 task force, pointed out that Covid infection is associated with an inflammatory response that can lead to arterial and venous thrombosis, besides other complications.

“Vaccines have been shown to reduce the severity of infection, inflammatory response to the virus and rates of serious complications,” he said to ThePrint.

According to Reddy, who is not directly associated with the study, while thrombotic events have been reported with virus vector vaccines and myocarditis with mRNA vaccines, incidence of life-threatening complications is far less compared to the benefit conferred of reduced risk of hospitalisation and death.

In this large multicentric study, said Reddy, the two vaccines used in India (Covishield and Covaxin) have not been shown to be associated with an increased risk of vascular clotting and sudden cardiac death.

“On the contrary, inadequate vaccination has emerged as a risk factor, explainable by lack of protection against severe disease, heightened inflammation and death,” he said. “Injudicious behaviors like vigorous exercise and binge drinking, overlaid against infection-related inflammation, can lead to plaque instability and rupture in coronary arteries, triggering thrombosis and precipitating heart attacks.”

“Incriminating vaccines as villains is unfounded, according to the Indian study which is consistent with global experience,” he stressed.

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What the study found

For the ICMR study, the hospitals prepared a line list of witnessed or unwitnessed deaths that occurred between 1 October, 2021, and 31 March, 2023, from hospital records, including death registers, medical certificates of cause of death and autopsy reports.

Two trained site physicians reviewed the records of witnessed deaths and determined their eligibility for the study as cases.

For unwitnessed deaths, the study investigators perused available records, or confirmed over telephone, or at the time of interview of the respondents, whether the deceased (case) was apparently healthy 24 hours before death.

The investigators then recruited controls that matched the age and gender from households neighbouring the residence of the case studies.

The majority of participants — 87 percent cases and 81 percent controls — had received at least one dose of Covid-19 vaccination any time before the outcome.

A small proportion, 2 percent of cases and 1 percent of controls, had been hospitalised for Covid. Of these, 2 percent of cases and 1 percent of controls had a history of post-Covid condition (PCC) at one month after the infection diagnosis.

Nearly 10 percent of the cases and 4 percent of the controls had a family history of sudden death. About 27 per cent of cases and 19 percent controls were smokers, and alcohol use was reported among 27 percent cases and 13 percent controls.

Among these, almost 7 per cent of cases and a little over 1 percent of the controls reported binge drinking 48 hours before death or interview. Vigorous intensity physical activity in the past one year was reported by 18 percent of cases and 17 percent of controls

The study found that patients with unexplained sudden death were four times more likely to have been hospitalised for Covid-19 and family history of sudden death was almost three times more likely to be associated with unexplained sudden death.

“Lifestyle factors such as current smoking status, alcohol use frequency, recent binge drinking, recreational drug/substance use and vigorous-intensity activity were positively associated with unexplained sudden death,” says the study.

The study showed that a single dose of the Covid-19 vaccine did not show a statistically significant protective effect, while receipt of two doses of vaccine was associated with lower odds of unexplained sudden death.

(Edited by Zinnia Ray Chaudhuri)

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