Delhi study says no evidence of Covid vaccines increasing heart attack risk; posits potential protective effect

An observational study conducted in Delhi found there is no discernible connection between the administration of Covid-19 vaccines and an increased risk of heart attacks.

BySumit Jha

Published Sep 06, 2023 | 9:00 AM Updated Sep 06, 2023 | 9:00 AM

Tragic rise in sudden cardiac arrest cases among young individuals calls for urgent awareness and preventive measures. (Creative Common)

In recent months, there have been reports of young and old individuals alike experiencing fatal heart attacks or cardiac arrests, allegedly linked to the Covid-19 vaccination.

However, when delving into the relationship between Covid-19 vaccinations and acute myocardial infarction (AMI), commonly known as a heart attack, researchers found there to be no such association.

Covid vaccines have protective benefits?

An observational study conducted in India has provided evidence that there is no discernible connection between the administration of Covid-19 vaccines — specifically Covishield and Covaxin — and an increased risk of heart attacks.

This study, which additionally highlights the protective benefits of these vaccines, was recently published in the journal PLOS One. Its primary objective was to investigate the impact of Covid-19 vaccination on mortality rates following an acute myocardial infarction (AMI) or heart attack.

“Our research outcomes affirm the safety of the vaccines in India. We uncovered no link between vaccination in India and an increased risk of heart attacks. In fact, our study revealed a noteworthy finding — individuals who had received the vaccine exhibited a reduced likelihood of succumbing to mortality following a heart attack,” Dr Mohit D Gupta, lead researcher of the study, told South First.

He added that, in essence, not only did their investigation establish the absence of any adverse connection between Covid-19 vaccinations and heart attacks, but it also hinted at a potential protective effect.

“This suggests that being vaccinated against Covid-19 may contribute to a lower risk of fatal outcomes subsequent to a heart attack,” stated Dr Gupta.

Also Read: 12 key symptoms commonly associated with long Covid-19

The retrospective study

The study used data from 1,578 people admitted to GB Pant Hospital in Delhi between August 2021 and August 2022. As many as 1,086 (68.8 percent) were vaccinated against Covid-19, while 492 (31.2 percent) were unvaccinated.

Among the vaccinated group, 1,047 (96 percent) had received two doses of the vaccine, while 39 (4 percent) had received only a single dose.

The adverse effects (AEs) of Covid-19 vaccines have mostly been mild, transient, and self-limiting. However, concerns have been raised regarding the cardiovascular adverse effects of these vaccines. Any side effect can have catastrophic effects, especially in large, densely-populated countries such as India, the authors noted in the study.

In all the enrolled patients, data regarding the patient’s vaccination status, including details of the type of vaccine, date of vaccination, and adverse effects, were obtained.

The researchers’ analysis did not show a specific clustering of heart attacks at any particular time post-vaccination, suggesting that there was no significant association between the Covid-19 jab and heart attacks.

Also Read: Have you heard of Eris, the new Covid variant in town?

Results of the follow-ups

When followed up 30 days later, all-cause mortality had occurred in 201 (12.7 percent) patients, with adjusted odds of mortality being significantly lower in the vaccinated group.

Similarly, at six months, those who were vaccinated and who had suffered a heart attack had lower odds of mortality compared to the non-vaccinated group.

The authors noted that Covid-19 vaccines showed a decrease in all-cause mortality at 30 days and six months following a heart attack. However, increasing age, diabetes, and history of smoking had a higher risk of 30-day mortality, the researchers stated.

“The findings of our study showed that the 30-day and six-month all-cause mortality risk was significantly lower in vaccinated subjects compared to the unvaccinated population,” the authors said.

This study is the first to be conducted among a larger population of AMI patients, which has shown Covid-19 vaccines to not only be safe, but also have a protective effect in terms of reduction of all-cause mortality — both on short term as well as at the six-month follow-up, the authors noted.

However, they also noted some limitations. This was a single-centre retrospective study and the findings need to be validated in further larger studies from different ethnic groups, they said.

Also Read: Is the surge in conjunctivitis cases due to new Covid-19 strain? 

Understanding what it means

Discussing with South First, physician and Co-Chairman of the National Indian Medical Association Covid Task Force, Dr Rajeev Jayadevan said that there are two notable Indian studies that have examined this topic of Covid-19 and mortality rate.

First, there is the ICMR study, where researchers examined a group of 14,419 individuals who were hospitalised for Covid-19 and survived their hospitalisation. The focus was on analysing the death rates among these individuals over the subsequent one-year period.

“What they found was quite significant. Among these individuals who had initially survived Covid, approximately 6.5 percent did not survive past a year after their hospitalisation. However, when the researchers further analysed the data, they discovered that those who had been vaccinated before their hospitalisation had a lower all-cause mortality rate over the subsequent year,” explained Dr Jayadevan.

He added that it is already well-established that vaccinated people are likely to survive a bout of Covid better than the unvaccinated. “But the ICMR study was the first to demonstrate that Covid-19 vaccination also reduces the mortality rate from all causes during the year following recovery from Covid,” said Dr Jayadevan.

Now, let’s shift our attention to the second study done by the researcher at GB Pant Hospital Delhi.

Breaking down what the study means, Dr Jayadevan said that this was a retrospective study, meaning that it involved looking back at historical patient records to analyse subsequent outcomes.

In this study, two key observations were made and it’s crucial to address them separately:

The first observation was that individuals, who had previously been vaccinated, had a lower overall mortality rate in the six months following a heart attack, indicating that vaccination was associated with improved survival rates.

“One possible explanation for the lower mortality rate among vaccinated individuals is the ‘healthy vaccine effect’. Those who choose to get vaccinated generally have healthier behaviours and lifestyles. They might be more health-conscious, engage in regular check-ups, and adopt healthier habits,” said Dr Jayadevan.

The second observation was intriguing. The researchers found no clustering of heart attacks following vaccination.

Also Read: Post-Covid individuals face elevated 1-year mortality risk, says study

What is clustering?

In medical terms, “clustering” means that a lot of people in the same place or community get sick with similar health problems at around the same time.

Imagine you and your friends all live in the same neighbourhood. One day, you all eat food from a new restaurant that just opened. The next day, several of you feel sick with stomach aches.

In medical terms, this would be like a “clustering” of stomach aches because a bunch of people in your neighbourhood got sick with the same problem around the same time. Doctors might investigate to see if there was something wrong with the food or if there’s a reason so many people got stomach aches after eating at the new restaurant. Clustering helps doctors find out what’s going on and how to keep everyone healthy.

So in this study, the researchers did not find AMI clustering post-Covid-19 vaccination.

“To illustrate this point, imagine a timeline stretching from 0 to 180 days, where each day represents a point on the timeline following vaccination. If heart-related events really occurred as a result of vaccination, you would see a significant concentration of events in a short time frame soon after vaccination. However, such clustering was not observed in the study, implying that vaccination is not causing heart attacks,” explained Dr Jayadevan.

He added that limitations apart, this large retrospective study provides strong circumstantial evidence that vaccination is not associated with an increased risk of heart attacks.

The key takeaway is that vaccination is not only a crucial tool in reducing Covid-19-related mortality and complications, but also reduces long-term death rates — even after recovery from Covid.

Also Read: WHO says Covid-19 is no more a global health emergency

Further down the research line

Covid-19 infection can have various negative effects on the cardiovascular system, such as causing heart problems like acute coronary syndrome (ACS), myocarditis, and heart failure. The impact of Covid-19 on the heart depends on how severe the illness is and whether someone has other health issues.

Now, let’s talk about the Covid-19 vaccines used in India. These vaccines have been shown to be effective at producing strong immune responses, both in terms of neutralising antibodies and T-cell responses. However, there hasn’t been a lot of research on how these vaccines specifically protect the cardiovascular system.

One small study did find that getting vaccinated against Covid-19 was linked to fewer hospital admissions for people with ACS, who were undergoing a specific heart procedure called percutaneous coronary intervention.

“Our current study has shown that people who had heart attacks and were vaccinated had a significantly lower risk of dying within 30 days or six months, compared to those who weren’t vaccinated. Furthermore, Covid-19 vaccines have been shown to reduce the risk of having a heart attack or stroke after getting infected with Covid-19,” the authors of the study said.

Also Read: Lancet study spotlights mental health impact of Covid-19

Data from large studies in Korea and the United States found that fully vaccinated people had a substantially lower risk of both heart attacks and ischemic strokes after contracting Covid-19.

The author also said that, in the past, there were some concerns that Covid-19 vaccines might increase the risk of heart attacks, but these worries were based on a few individual cases and not solid scientific studies. Some suggested reasons for this include blood clotting issues, allergic reactions to vaccine components, or stress-related events among elderly individuals getting the vaccine.

“However, recent and more extensive studies have failed to establish a clear link between Covid-19 vaccines and heart attacks. Postmortem examinations and investigations into sudden deaths following vaccination did not show a direct connection between the vaccine and heart problems,” said the authors of the recent study.