Covid-19 vaccines: Reported adverse effects not necessarily linked to shots

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  • Anyone can report health events after vaccination to monitoring systems, such as the Med Safety app in SA.
  • These reports may, however, contain information that is incomplete, inaccurate or coincidental.
  • Investigations have to be done to assess whether there is a causal link between the vaccine and the event.

Covid-19 vaccines have been proven to be safe and effective. More than six billion people have received these vaccines. Data have also indicated that in the majority of cases, people experience only mild (but normal) side effects after vaccination, such as pain or swelling at the injection site.

A very small number of people have been shown to develop serious and potentially fatal events after vaccination, such as thromboembolic events (blood clots) after vaccination with the Oxford-AstraZeneca and Johnson & Johnson vaccines. A risk-benefit analysis remains overwhelmingly in favour of the continued use of the vaccines, but to ensure the integrity of their development, its vital for evaluation and monitoring processes to be in place.  

A detrimental health event occuring after vaccination is known as an "adverse event following immunisation" (AEFI), as described by the National Institute of Communicable Disease (NICD). However, health events may or may not be caused by the vaccine, and only a follow-up investigation after receiving a report can determine whether the vaccine was responsible for the event.

An example of an AEFI, notes the NICD, is when a person receives a Covid vaccine and then has a stroke, a heart attack or dies in a motor vehicle accident. While these events may or may not be associated with vaccination, they're all described as "AEFIs", it explains.

In South Africa, reporting can be done at the health facility delivering the vaccine, or by using the Med Safety app, which is freely available to download. In the US, these reports can be submitted to the Vaccine Adverse Event Reporting System (VAERS). Importantly, however, these reports alone cannot be used to determine if the Covid vaccine caused or contributed to an adverse event or illness. 

Reports contain incomplete, inaccurate info

As mentioned on the VAERS website, the reports may contain incomplete or inaccurate information.

“In large part, reports to VAERS are voluntary, which means they are subject to biases. This creates specific limitations on how the data can be used scientifically. Data from VAERS reports should always be interpreted with these limitations in mind,” it says.

Earlier this year, an article published by Science Magazine pointed to one of VAERS's strengths – its openness – also becoming a potential weakness, since anyone who receives a vaccine in the US can report an adverse event to the system. The openness, it said, ensured that VAERS received plentiful reports.

Since December 2020, it has garnered more than 228 000 reports for Covid vaccines, which was more than four times the number received in the entire 2020 for all vaccines. There are concerns that this openness can be used to spook the public, since people can misinterpret the information “as a catalogue of actual side effects, rather than possible or suspected ones,” the article noted.

Clear messaging

To counter any misinterpretation of this information, the VAERS website stresses that the reports do not imply causality, and that many events could have happened by coincidence. 

Similarly, the South African Health Products Regulatory Authority’s (Sahpra) adverse events following immunisation (AEFIs) microsite states: “It is important to note that the adverse events following immunisation (AEFIs) reported on this site have not been assessed for causality (unless specified), and therefore, the events may not necessarily have a causal relationship with the administration of the vaccines.

Mafora Matlala, Sahpra’s Pharmacovigilance manager, recently explained that the reports Sahpra receives in its system are referred to as adverse drug events. 

“However, when we do the assessment, we are trying to identify those that are actually adverse drug reactions to say, ‘Yes, definitely, there’s a suspected causal relationship between the drug [or vaccine] and a reaction,’" she explained.

Coincidental to vaccination

Since the reports vary in quality and completeness, there will also be ones that are classified as “coincidental to vaccination”.  For example, people will experience health problems following vaccination that would have occurred irrespective of whether the person got the vaccine, which means those health problems are not related to the vaccine, explains the Centers for Disease Control and Prevention (CDC).

Professor Hannelie Meyer, NISEC committee chairperson, previously highlighted that an event that is followed by vaccination does not mean it was caused by vaccination, Health24 reported.  

“It is human nature to put it, or blame things, on a single, major cause. And we often make the mistake of blaming something that occurred earlier … where we assume that one event must be the cause of a related event simply because it occurred earlier,” she said, although this may not always be the case. 

Meyer said that it’s common for adverse events to take place coincidentally with the vaccination. “The reason for that is that people have comorbidities. We are vaccinating large populations of people, and many of them are in the older age groups with comorbidities,” she said.   

Therefore, like in the reporting and monitoring systems of both Sahpra and VAERS, we should bear in mind that in any reported event, no cause-and-effect relationship has been established, unless stated otherwise. 

Sahpra’s data

According to recent reporting by News24, the Western Cape has had 645 reports of adverse effects after vaccination. Around 80% of these were minor reactions, such as headaches and body pain, and more than 400 people had recovered.

All 32 deaths recorded in the Western Cape in people who had been vaccinated were investigated and no link was found to the Covid vaccines. 

"In all deaths where the investigations have been completed, the vaccine did not cause the death and the death was confirmed to be due to another cause, such as illness or injury," said Western Cape health department chief operating officer Saadiq Kariem.

To date, Sahpra found no deaths linked to the vaccine.

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

READ | Refresher: How to report adverse events after Covid vaccination – and what follows

READ | Covid-19: Here's how you can report adverse vaccine effects to Sahpra

READ | Covid-19 vaccination: The danger of spreading anecdotal reports with few facts and no investigation

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