Covid vaccines were developed quickly: How do we know they won't cause any long-term health effects?

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  • The Covid-19 vaccines were developed very quickly, prompting concerns about potential long-term side effects.
  • But history indicates that if severe side effects occur, they usually happen within the first two months after vaccination.
  • Vaccine technologies used in the Covid-19 vaccines have previously been used to protect against other infectious diseases, and have good safety records.

The Covid-19 vaccines were developed in record time, which is considered to be a remarkable achievement in the field of medical science. On the other hand, this has led to concerns among the public about their safety, particularly regarding potential long-term side effects. 

However, as this article published in Nature explains, the rapid development and rollout of the vaccines were based on years of previous research on related viruses and faster ways to manufacture vaccines, as well as huge amounts of funding that allowed developers to fast-track multiple clinical studies in parallel, also with health regulators moving more quickly than usual. 

Health24 spoke to Professor Thomas Scriba, deputy director of immunology and laboratory director at the South African Tuberculosis Vaccine Initiative, University of Cape Town, about the knowns and unknowns regarding the safety of these vaccines.

Side effects unlikely to occur

“First of all, it is well known, based on decades of experience with many dozens of vaccines, that the vast majority of adverse events (side effects) occur in the period immediately after vaccination (typically during the first two months),” said Scriba. 

He added that this is not a surprising finding, given that the injected vaccine material is typically eliminated from the body within a few days.

“It is extremely rare that side effects occur after this,” he said. And so, while it is true that the available safety data on the Covid-19 vaccines extend at most to one year after vaccination, the risk of any new adverse events occurring more than a few months after vaccination is extremely small, he explained.

Sahpra monitoring reported side effects

The South African Health Products Regulatory Authority (Sahpra) recently launched a free mobile-based application that allows individuals to report any adverse side effects to several medicines and therapies, including the Covid-19 vaccines, Health24 reported

Named the Med Safety App, it will help to create awareness of various medicines, their potential adverse effects, and pharmacovigilance (the practice of monitoring the effects of medicines registered for use). 

“The purpose of the data reported through the Med Safety App is to contribute to the understanding of medicines’ safety profiles of marketed medicines, including that of Covid-19 vaccines,” the website explains. 

Participants from the Pfizer Covid-19 vaccine trials will also be monitored for two years after their second dose, Dr Bha Ndungane-Tlakula, Country Medical Director at Pfizer South Africa, told Health24

Similarly, trial participants (frontline healthcare workers) from the Johnson & Johnson Sisonke study in South Africa will also be followed for two years until May 2023, said the study’s co-lead investigator, Professor Linda-Gail Bekker. 

Both vaccines are currently being administered in South Africa.

Safety data encouraging

Another reassuring factor is that there is a lot of safety data available (that extend years after vaccination) for vaccines that have been tested against other infectious diseases, and use the same technology as in some of the Covid-19 vaccines, said Scriba. 

These include adenoviral technology (used in the Johnson & Johnson and AstraZeneca-Oxford Covid vaccines) and mRNA technology (used in the Pfizer-BioNTech and Moderna vaccines). 

The vaccines for influenza (flu) and Ebola, for example, have incorporated this technology and the safety data confirm that long-term side effects are extremely rare, explained Scriba.

Similarly, a number of vaccine candidates for the Zika virus have been in development, including one that uses mRNA technology.

What the CDC says

According to the US Centers for Disease Control and Prevention (CDC), serious, long-term side effects are extremely unlikely following any vaccination, including Covid-19 vaccination. 

“Vaccine monitoring has historically shown that side effects generally happen within six weeks of receiving a vaccine dose,” the CDC states

As important as it is to consider the potential long-term effects of the Covid-19 vaccines, it is also critical to think about the long-term effects of Covid-19 itself. Although most people with Covid-19 recover within a few weeks, emerging evidence indicates that some survivors, known as “long haulers”, still experience health issues months after the initial infection has passed.  

“Whatever the concern about the risks of side effects due to vaccination, it is indisputable that these risks are insignificant when compared with the long-term and much more serious effects of Covid-19 disease (which the vaccines prevent very effectively),” said Scriba.

*For more Covid-19 research, science, and news, click here. You can also sign up for our Daily Dose newsletter here.

READ | Can the Covid-19 vaccines cause infertility, miscarriage? Experts explain

READ | Covid-19 vaccine myths debunked: Get the facts here

READ | Sahpra’s Covid-19 vaccine approval process: ‘The safety of the public takes precedence’

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