Explained: How Much Do We Know About COVID-19 Vaccine Side Effects?

Yes, rare adverse events from COVID-19 vaccines is a real possibility. But there's more to it.

COVID-19 vaccine side effects

(Photo: Vibhushita Singh/FIT)

Recent reports of adverse events from Covaxin and Covishield COVID-19 vaccines have once again thrown up questions about how safe the vaccines we took during the pandemic really are.

Can you still develop side effects from the vaccine?

What are the long-term effects of these COVID vaccines?

Can the COVID-19 vaccines lead to a heart attack or a stroke now?

...these are some questions floating around the internet, and the memes, misinformation, fearmongering posts and exaggerated reports by the media surrounding the topic do not help.

What do we know about COVID-19 vaccine side effects? What does the science say?

To break it down for you, FIT spoke to experts on the topic - Dr Anurag Agarwal, Dean, Biosciences and Health Research, Trivedi School of Biosciences, Ashoka University, Dr Vineeta Bal, Immunologist, and researcher at the Indian Institute of Science Education and Research (IISER Pune), and Amar Jesani, Editor, Indian Journal of Medical Ethics.

'Side Effects From Vaccines Are Normal'

Experts have said this before, but just to reiterate, side effects from vaccines are common. This is normal.

"Very minor side effects are very common. The person who gets the vaccine usually has redness around the place of inoculation, and pain in the arm. They can occur in up to 90 percent of the cases," says Dr Vineeta Bal.

These side effects are actually even desirable, she says.

"The idea with the vaccine itself is that it should cause local inflammation. That inflammation is required for triggering an immune response. This is intended injury."

Dr Vineeta Bal, researcher, IISER Pune

But, in some rare cases, all vaccines (and even medicines) can cause some rare adverse events, and you're not crazy for worrying about them.

However, the good news is that they are 'very rare'. "If they are anything but very rare, the vaccine is not approved," says Dr Anurag Agarwal.

COVID Vaccines and Adverse Effects: What We Know

One of the most talked about adverse events linked to COVID-19 is Thrombosis with thrombocytopenia syndrome (TTS) or blood clots leading to neurological issues and in some cases, even death.

Back in 2021, TTS was first linked to the Johnson and Johnson vaccine in the US. This was followed by cases of thrombosis linked to the AstraZeneca vaccine after which the vaccine was temporarily halted in some countries in the European Union.

"It could be the problem of the platform of these vaccines," says Dr Agarwal. Both J&J and AstraZeneca (Covishield) are adenoviral vector vaccines.

Does this mean you should worry about developing TTS if you received Covishield? Not quite.

Both Dr Agarwal and Dr Bal say that if the TTS is vaccine-induced, it's not likely to occur years after inoculation.

"It is likely caused because of induction of antibodies that the vaccine triggers which goes down with time. so it (Vaccine-induced TTS) shouldn’t occur with time."

Dr Anurag Agarwal

"Getting panicky in retrospect is unnecessary, and creates unnecessary apprehension in the community," adds Dr Bal.

What We Don't Know

What about other health issues like heart attacks, stroke and respiratory issues that are being associated with COVID vaccines?

For instance, a recent observational study by researchers at Banaras Hindu University found that nearly 30 percent of people who took Bharat Biotech's Covaxin experienced ‘adverse events of special interest’ (AESI), such as stroke and Guillain-Barre syndrome.

Although the study made headlines and sparked online chatter, however, it is not without its limitations.

For one, according to Dr Vineeta Bal, in such cases, it is very difficult to link illnesses to vaccines two or three years down the line, "Because there is no direct causality that can be established."

"This is common to many of the drugs and vaccines. If you’re taking a drug with some known side effects then ten years down the road something happens, can we establish cause and effect relationship? Normally not. "

Dr Vineeta Bal

This isn't just a shortfall of the BHU study, but the adverse effects reporting system in general, says Dr Agarwal.

"It simply tells you have people who received the vaccine reported all these things. Whether the vaccine caused these things cannot be determined even in a three-week, four-week period unless you have proper data of similar things being reported elsewhere."."

Experts FIT spoke to say that if anything, this gap underscores the need for more robust research on adverse effects of the vaccine.

The Indian Council of Medical Research (ICMR) responded to the BHU study by distancing itself from it, calling it a “poorly designed study”

Commenting on ICMR's response, public health and bioethics expert Dr Amar Jesani says if ICMR says the study has flaws, which it does by the admission of its own researches, why doesn't ICMR have scientific data to counter its findings?

"ICMR has the money and the resources to do a long-term study on the adverse events linked to both Covaxin and Covishield. If they had taken it on, they could have come up with very robust data."

Dr Amar Jesani

He goes on to say that back in January 2021, when Covaxin became the first COVID vaccines to be administered in India, there had been some deaths reported among healthcare workers (the first group to be vaccinated) that could potentially be linked to the vaccine but was never confirmed.

"Several of us from the public health sector came together at the time and wrote two open letters to the health minister and the AESI (Adverse Events of Special Interest) asking for an investigation, a specialised autopsy of those who died." However, he says, nothing came of it.

Risk, Benefit and Alternative

According to Dr Agarwal, deciding to take a drug or a vaccine is a matter of weighing the risks, benefits and alternatives.

Yes, there is some risks associated with any vaccine, however, "the risks we are talking about are very small compared to the ones that we are faced with daily," he says.

For instance, he explains, the risk of dying annually from road accidents was more than the risk of thrombosis even in the most vulnerable population.  

Moreover, when vaccinated and unvaccinated people were compared, the risk of heart attack and stroke, between vaccinated and unvaccinated people was consistently found to be highest in unvaccinated people.

"So on the whole, the vaccine actually saved people from stroke rather than caused stroke," adds Dr Agarwal.

While the experts FIT spoke to reassure that there isn't cause for panic, in the same breath they also recognised that there is a need to be an attempt to find answers for the tiny minority of people affected.

'What of Those Who Do Get Adverse Effects?'

Experts say that a lack of transparency is a major reason for wavering trust in the vaccines.

According to Dr Jesani, if health authorities want to instill trust in the vaccines and public health initiatives like mass inoculation drives on the whole, they need to be more open and have a system for redressal.

"You are taking a very small risk when you get vaccinated, but if the risk affects you, and you turn out to be the one in a thousand that gets it, then what happens?" he says.

People need to know that in case if something happens to them, in case they're the rare case having an adverse event, there is a government and a healthcare system to take care of them."

Dr Amar Jesani

The groundwork for such a system, for all vaccines, has already begun in parts of India.

For instance, the Karnataka health department has said that they are making a provision for treatment of all adverse events following immunisation (AEFI) under the health scheme.

More robust monitoring, data collection, and effective communication can help reinstall trust in the vaccine, concludes Dr Jesani.