Covid-19: Amid growing concerns about their adverse effects, your basic guide to understanding mRNA vaccines

According to the physician, his team and he “have multiple autopsy studies that provide essentially conclusive evidence that vaccines are inducing sudden cardiac deaths”. “Yet the rate of these vaccine-induced deaths remains unknown. While many nations which have been using mRNA have experienced increased mortality, more people dying than should be expected in the past years, which co-relates with the time of the initial vaccine rollout and then booster campaigns. While the cause is not known yet, researchers analysing this data were unable to identify any other reasonable cause of the excess deaths other than the vaccines,” he claimed, warranting further detailed clinical trials of mRNA which can clearly show the benefits far outweigh the threats.

Against the backdrop of this recent revelation, let’s understand more about mRNA vaccines and their efficacy in the fight against Covid-19.

What are vaccines?

Vaccines help prevent infection by preparing the body to fight foreign pathogens like bacteria, viruses, etc. All vaccines introduce a harmless piece of a particular bacteria or virus into the body, triggering an immune response.

As the Covid-19 pandemic spread, an mRNA vaccine candidate was the first to enter human trials globally. The first two vaccines that were made available for use in the US were based on mRNA technology — Pfizer-BioNTech and Moderna.

How are they designed?

World Health Organization notes that there are three main approaches to designing a vaccine. “Their differences lie in whether they use a whole virus or bacterium (inactivated vaccine or a live-attenuated vaccine); just the parts of the germ that triggers the immune system (Viral vector vaccine like CoviShield); or just the genetic material that provides the instructions for making specific proteins and not the whole virus” (The genetic approach (nucleic acid vaccine).

WHO notes that there are three main approaches to designing a vaccine. (Reuters)

What is mRNA?

Dr Devashish Desai, consultant, infectious diseases, Ruby Hall Clinic, Pune, in a conversation with indianexpress.com, explained that instead of putting a weakened germ into our bodies to generate an immune response from our human bodies, mRNA or the messenger Ribonucleic acid use a laboratory created genetic molecule to teach our cells to make a S-protein or spike protein — found on the surface of the Covid-19 virus. Post-vaccination, the muscle cells begin making S-protein and display them on the surfaces that is known to help trigger immune response that produces antibodies against the pathogen, in this case, SARS-CoV-2.

But mRNA is not a new genetic development in the view of Covid-19. According to WHO, while the immunostimulatory effects of RNA have been known for nearly 60 years, the possibility of using direct in vivo administration of in vitro transcribed messenger RNA (mRNA) as a means to temporarily introduce genes expressing proteins (including antigens) was demonstrated in 1990 following direct injection of “naked” nucleic acids. “Subsequent improvements to stabilise mRNA, to increase the feasibility to manufacture RNA-based products and to decrease RNA-associated inflammatory responses have led to significant advances in the development of mRNA vaccines and therapeutics,” it notes on its website.

However, WHO — in a January 2021 report — notes that before the Covid-19 pandemic, none of the nucleic acid based vaccines had yet been through the full approvals process for use in humans, though some DNA vaccines, including for particular cancers, were undergoing human trials. “Because of the pandemic, research in this area has progressed very fast and some mRNA vaccines for Covid-19 are getting emergency use authorisation, which means they can now be given to people beyond using them only in clinical trials”.

So, are they safe?

Pfizer-BioNTech and Moderna Covid-19 vaccines were found to be highly effective against symptomatic and severe Covid-19 disease by the original strain of SARS-CoV-2. “Effectiveness of mRNA vaccine against SARS-CoV-2 variants of concern was found to be lower compared to its effectiveness against original strain of SARS-CoV-2,” Dr Shilpa V Naik, infection control officer and consultant microbiologist, Bhatia Hospital Mumbai told indianexpress.com.

According to Dr Naik, death due to blood clots with low platelets (thrombosis with thrombocytopenia syndrome, or TTS) at a rate of about four cases per million was caused by Janssen’s Johnson and Johnson doses. While mentioning that studies have shown Pfizer-BioNTech and Moderna vaccines to be associated with the risk of myocarditis and pericarditis in individuals aged 18-39 years of age, Dr Naik said that “safety investigations state that risk of myocarditis is much higher after Covid-19 infection than after vaccination”.

Dr Desai too noted that the benefits far outweigh the risks which are known to affect 1 in 800 cases due to various reasons which studies have shown to be the case with viral vector vaccines too.

Dr Sanjith Saseedharan, consultant and head-critical care, SL Raheja Hospital, Mahim-A Fortis Associate, said that if at all there is any harm, “it is usually noticed in the first six weeks of getting the shot”. The benefits, in comparison, are for an extended duration of time which may span months at a stretch. “Yes, these vaccines do have a significant serious adverse event rate when compared to the swine flu and rotaviral vaccination. But since there is ‘limited follow-up time’, the harm-benefit ratio is skewed towards harm,” he said referring to the June 2022 Lancet study.

“Moreover, if one is admitted to the ICU or hospital, this would be counted as an admission. Whereas, the serious adverse event would be counted on per event basis. Thus, there would ideally be a large number that has been prevented from hospital admission compared to a much smaller vaccine-associated serious adverse event. This forms a serious methodological flaw in data collection,” mentioned Dr Saseedharan.

Hence, unless patient-level data is available with long-term follow-ups, such data cannot be taken as absolutely right, and thus does not demand any hasty action or change of protocol, Dr Saseedharan stressed.

“What is clear from worldwide data is that vaccines have definitely helped in stemming the pandemic as those countries that have had a high proportion of vaccinated individuals, and have managed to reduce the Covid-19 illness spread and admission by reducing the burden on healthcare and the economy. The important fact that we all should understand is that Covid-19 vaccines were all approved only after they underwent extensive studies and tests for safety and efficacy, with a clear indication that vaccines do give a good deal of protection from serious Covid-19 illness,” Dr Saseedharan said.

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