Provocative headlines on a post-COVID vaccination syndrome

Helen Petousis-Harris, BSc, PGDipSci (Dist), PhD

7 August 2023

There are headlines, reports, and social media posts about a post-COVID vaccination syndrome.
Diving into the detail reveals limited evidence to support such a syndrome.
Studies show that COVID-19 vaccines are associated with a reduction in the development of long-COVID.

Vaccines authorised for use are incredibly safe, but the risk for serious side effects is not ‘0’. Vaccine safety scientists exist because vaccines are not 100% safe. Just to be clear, nothing in the multi-verse is 100% safe but vaccines can come pretty close.

A feature of large vaccination campaigns is that many people are being vaccinated at any one time. This means that many people happen to have had a vaccine prior to any adverse experience that occurs for them in the day and weeks following. COVID-19 has seen the largest number of people vaccinated over a short period in history and this resulted in the detection of rare side effects quite early on. Those of note are:

Increased risk of myocarditis and pericarditis (inflammation of or around the heart) associated with mRNA vaccines, more common in young males after the second dose.
A new syndrome of thrombosis with thrombocytopenia (blood clots with low blood clotting factors) associated with viral vector vaccines, more common in older women after the first dose.
Guillain-Barré syndrome (a neurological condition) associated with viral vector vaccines. This is extremely rare.

The risks of COVID-19 disease are far greater than risks posed by the vaccines.

During the early stages of COVID-19 vaccine roll out there were case reports of chronic fatigue-pain like symptoms occurring in people recently vaccinated. The big question is – did this have anything to do with the vaccine? Short answer – possibly, this can never be ruled out, but for the vast majority it is unlikely.

Here is what we know.

Prior to COVID-19, chronic fatigue syndrome affected around 5–9 million in the U.S. and around 17–24 million worldwide across all age groups, races, ethnicities, and socioeconomic groups. That is a lot of people. The symptoms are fairly consistent with those of long-COVID and since the pandemic people suffering with chronic illness has skyrocketed. One of the major causes is known to be a viral illness such as Epstein Barr or herpes viruses. Also stress and other things that can affect the immune system.

Click here to read more about myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) on Solve M.E.

Given one of the suspected mechanisms of chronic fatigue syndrome is infection, for decades some people have linked vaccines with these outcomes, as they trigger the immune system, by design. However, the hypothesis lacks epidemiological evidence. While it cannot be definitively proven that a vaccine is not a trigger what we can say is that there is no convincing evidence that they increase the population’s risk – None of them.

So, what about “post-COVID vaccination syndrome”?

There have been case reports describing such a syndrome. However, this does not mean that a patient’s symptoms were caused by a vaccine. There could be other explanations such as:

Infection with SARS-CoV-2, most of the world's population have been infected.
Infection with another virus or bacteria, these are still alive and well.
Stress or other factor perturbing the immune system.

The only way to determine if COVID-19 vaccines increase the risk for a chronic fatigue-like syndrome is to examine the existing evidence, and to also conduct studies that compare the risk in people exposed and unexposed to the vaccine.

After over 13 billion doses of COVID-19 vaccines administered all over the world, at this time the epidemiological evidence on COVID-19 vaccines and chronic-fatigue-like symptoms shows that:

Vaccines reduce the risk of developing these symptoms compared with unvaccinated people.^1,2
Vaccination of people with these symptoms does not appear to exacerbate the symptoms and some evidence suggests it may result in some relief.^2,3
Vaccine safety scientists continue to remain alert for adverse events of concern.

Key messages for patients:

COVID-19 disease carries a risk for developing long-COVID and vaccines have been shown to reduce this risk.
There are some known risks associated with COVID-19 vaccines, these are extremely rare, the risks from COVID-19 disease are far greater.
There have been headlines and reports of a fatigue syndrome associated with COVID-19 vaccines.
So far, even after over 13 billion doses of vaccine, there is no evidence to indicate vaccines increase the risk for a chronic fatigue-like syndrome.

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Here is what we know.

So, what about “post-COVID vaccination syndrome”?

Key messages for patients:

Further reading on COVID-19 vaccination and long-COVID