You may have heard of several side effects of the COVID-19 vaccine. But appendicitis probably isn’t one of them.

While appendicitis has been documented after the COVID-19 vaccine, it’s still unclear whether it’s an adverse vaccine effect. Research into this topic has returned mixed results.

Below, we’ll cover more about appendicitis, its potential connection with the COVID-19 vaccine, and its known COVID-19 vaccine side effects. Keep reading to discover more.

Appendicitis happens when your appendix becomes inflamed. Your appendix is a hollow pouch attached to your large intestine. It’s in the lower right-hand area of your abdomen.

When the opening of the appendix becomes blocked, it can lead to appendicitis. Some things that can cause blockages include:

Sometimes the exact cause of appendicitis is unknown. Regardless, blocking the opening of the appendix leads to a buildup of bacteria and inflammation. This causes symptoms like:

Appendicitis is a medical emergency. If it’s not treated promptly, the appendix can burst, causing severe and potentially life threatening complications like peritonitis and abscess formation.

Appendicitis has been reported after COVID-19 vaccination. One possible mechanism for this could be enlarged or swollen lymph nodes in the body following vaccination.

Research on this topic is conflicting. Some data indicate appendicitis may be a potential adverse effect of vaccination, while others note that the risk of appendicitis after vaccination is no higher than in the general population.

Appendicitis detected in COVID-19 vaccine trials

Appendicitis was noted in the large-scale clinical trial of the Pfizer-BioNTech mRNA COVID-19 vaccine. Out of 43,448 trial participants, 8 in the vaccine group and 4 in the placebo group experienced appendicitis.

These cases were considered unrelated to vaccination. This is because they didn’t happen more frequently than is expected within the general population.

Research pointing to appendicitis being an adverse effect of COVID-19 vaccine

A 2021 study looked into the adverse effects of the Pfizer-BioNTech vaccine in over 1.7 million people in Israel. Researchers used a matched group of vaccinated and unvaccinated individuals for each adverse effect.

The adverse effect with the strongest association with vaccination was myocarditis. But researchers also found an increased risk of swollen lymph nodes and appendicitis.

Another 2021 study looked into appendicitis after COVID-19 vaccination using a World Health Organization (WHO) database. At the time of the study, researchers estimated that 1.82 billion vaccine doses had been given worldwide.

From the database, researchers were able to find 334 unique reports of appendicitis after vaccination. Most of these were associated with mRNA vaccines and occurred 0 to 4 days after vaccination.

The researchers found that the number of appendicitis cases after vaccination was slightly higher than expected. They concluded that appendicitis was a possible adverse effect of COVID-19 vaccination but that more research was needed.

Research pointing to appendicitis NOT being an adverse effect of COVID-19 vaccine

A 2021 study disagreed with the findings above. In this study, researchers in the United States evaluated vaccine safety data from the Vaccine Safety Datalink for 23 adverse effects.

A total of 11,845,128 mRNA vaccine doses given to 6.2 million people were included in the study. Researchers found that the incidence of appendicitis in people getting an mRNA vaccine was not significantly higher than expected.

A 2022 study looked into appendicitis and COVID-19 vaccination in a large cohort of people in Denmark. Researchers compared over 4 million people vaccinated with an mRNA vaccine to an unvaccinated reference group.

It was found that appendicitis occurred at about 8 cases per 100,000 vaccinated people. When this rate was compared with the rate of appendicitis in the unvaccinated reference group, no significant difference was found.

Bottom line

Appendicitis has been reported after COVID-19 vaccination, but research into this area is mixed. Some researchers have found that appendicitis may possibly be an adverse effect of COVID-19 vaccination.

But others have not found an association between COVID-19 vaccines and appendicitis risk. Overall, more research is needed to either confirm or eliminate appendicitis as an adverse effect of COVID-19 vaccines.

According to the Centers for Disease Control and Prevention (CDC), the most common side effects of the COVID-19 vaccine are:

  • swelling, redness, or pain at the injection site
  • fatigue
  • fever, with or without chills
  • muscle aches
  • headache
  • nausea

These side effects are a sign that your immune system is building a response to the vaccine. Vaccine side effects typically go away on their own within a few days. In the meantime, you can help to ease them by:

  • staying hydrated
  • resting up
  • placing a cool compress over the injection site
  • taking over-the-counter (OTC) medications like acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) for symptoms like fever and aches and pains

If your side effects don’t go away within a few days or begin to get worse, contact a doctor.

COVID-19 vaccines are safe and effective at preventing severe illness, hospitalization, and death due to COVID-19. As such, the CDC currently recommends COVID-19 vaccines and boosters for everyone ages 5 and older.

Vaccination is particularly essential for people at an increased risk of severe COVID-19 illness. This includes, but isn’t limited to, individuals who are immunocompromised and those with medical conditions like:

Getting immunity through vaccination is also safer than getting immunity by having COVID-19. Contracting SARS-CoV-2, the virus that causes COVID-19, can cause severe illness in some people and lead to long-term health issues, including long COVID.

While any treatment, medication, or vaccine comes with risks, the risks of serious complications due to COVID-19 are extremely low. This includes appendicitis.

For example, according to the CDC, anaphylaxis occurs in only 5 out of every 1 million vaccine doses. Further, out of over 55 million vaccine doses given to people under age 18, only 647 cases of myocarditis have been confirmed.

While appendicitis has been reported following the COVID-19 vaccine, it’s not entirely clear whether it’s an actual adverse effect of vaccination. Research results have been mixed on this topic, and more research is needed overall.

Regardless, appendicitis after vaccination has happened very rarely.

Overall, the benefits of receiving a COVID-19 vaccine outweigh the potential risks. If you have concerns about the COVID-19 vaccine, discuss them with a doctor.