COVID-19 Vaccine Surveillance- November update

Adverse effects of COVID-19 vaccines – what are they?

Mass vaccinations against COVID-19 are being done around the globe. As of 3rd November 2021, over 7.1 billion doses of the COVID-19 vaccine have been administered throughout the world. Before their approval, these vaccines went through rigorous clinical trials and were found to be safe. Their administration to the general population on such a large scale has uncovered some adverse effects. However, most of the adverse effects are minor such as pain at the site of injection, headache, fatigue, and muscle pain.

Figure 1:Most COVID-19 vaccinations do not cause any significant adverse effect.

[Image Credit: Wikipedia].

The major adverse effects are extremely rare which include anaphylaxis, vaccine‑induced immune thrombotic thrombocytopenia (VITT), myocarditis, and pericarditis. These latter disorders are by far the most important adverse effects caused by COVID-19 vaccines. Some other adverse effects include skin reactions, Bell’s palsy, rhabdomyolysis, vasculitis, pityriasis-rosea, reactivation of herpes simplex, varicella-zoster, reactivation of hepatitis C, ocular adverse effects, stroke, myelitis, and more. People with a history of chronic diseases and those who have previously been exposed to SARS-COV 2 are at greater risk to these reactions. Studies have also found that these adverse effects are slightly more prevalent in women. The exact type of adverse effect depends upon the medical history, age, and gender of the individual as well as the type and dose of the vaccine administered. The following are the developments in the understanding of some of the previously known adverse effects:


Anaphylaxis is a potentially life-threatening allergic reaction that occurs minutes after receiving the COVID-19 vaccine. Anaphylaxis is one of the earliest reported adverse effects due to the COVID-19 vaccination. It is being hypothesized that anaphylaxis can occur due to the formation of a polyethylene glycol (PEG)-conjugated lipid derivative triggered by mRNA vaccines. This explains an observed trend that females are more susceptible to this allergic reaction. Hormonal differences can also be one of the contributing factors for the adverse reaction of anaphylaxis.


Myocarditis is the inflammation of the walls of the heart. It is also one of the earliest reported adverse effects of COVID-19 vaccines. Myocarditis is more prevalent in males of younger age who received Pfizer/BioNTech, Moderna, or Janssen vaccine. According to a hypothesis, myocarditis is somehow associated with IFN-gamma and TNF-alpha. This hypothesis also explains the observed trend in terms of the age and gender of the affected individuals.

Neurological Adverse Effects

There are a variety of neurological adverse effects which occur following COVID-19 immunization. These include Guillain-Barre syndrome, Bell’s palsy, venous sinus thrombosis, and acute transverse myelitis. It is difficult to draw a causal association between such a wide spectrum of neurological adverse effects and COVID-19 vaccines, but identification of risk factors can reduce the incidence of these unwanted events. Patone et al. compared the risk of neurological disorders caused by the COVID-19 virus to the neurological adverse effects caused by the vaccines in an important review. The article reported that neurological complications of COVID-19 infection are much more prevalent than the adverse effects of the vaccines. This is an encouraging finding for the general population concerned about the devastating neurological adverse effects caused by COVID-19 vaccination.

Recommendations regarding Vaccination

Although the exact mechanisms of many of the adverse effects are still unknown, the epidemiological data can be used to understand certain patterns about these adverse effects which can help us prevent these events. Some recommendations are given below:

Deaths after COVID-19 vaccine

About 9,367 deaths following COVID-19 vaccination have been reported to the Vaccine Adverse Event Reporting System (VAERS). It is important to note that these deaths do not necessarily have a causal relationship with COVID-19 vaccination. They only have a temporal association with the administration of either the first or second dose of the vaccine. Schneider et al. performed an autopsy investigation on 18 individuals who died after receiving a shot of the COVID-19 vaccine. The authors reported that 13 of these 18 individuals died due to pre-existing diseases which were not related to the COVID-19 vaccine. The exact cause of death of the remaining 4 individuals and the vaccine administered is given in the table below:


Vaccine administered

Number of deaths









Table 1: Data from the autopsy investigation performed by Schneider et al.


The benefits of COVID-19 vaccines clearly outweigh their potential risks. Mass vaccination is still the best way out of this pandemic. The transparency regarding the reporting of adverse effects of COVID-19 vaccines is essential to this mass vaccination strategy. It also allows to point out some general patterns so that at-risk individuals can take proper preventive measures.

Written by: Numair Arshad