Herpes zoster, more commonly known as shingles, is a viral infection that occurs when the chickenpox virus (called varicella zoster') reactivates in our bodies. After a chickenpox infection, usually during childhood, the virus still hides out in our nerves to potentially reappear years or decades later, as shingles. Shingles causes a painful rash that can last for weeks or months. In rare severe cases, nerve pain can persist for months or years after the rash goes away.

In the United States, there is a one in three chance of developing shingles, with the risk increasing as age increases, particularly after age 50. These rates are measured to be relatively similar globally. The chances of getting shingles decrease significantly if you’ve received one of the two available vaccines to prevent shingles: Shingrix or Zostavax. Shingrix has been shown to be 97% effective at preventing shingles in adults aged 50 to 69 years old, and Zostavax has been shown to be 70% effective at preventing shingles in the same age group.

No evidence demonstrates that COVID-19 vaccines cause shingles, either from data the original COVID-19 vaccine clinical trials or from data in studies following the distribution of the approved vaccines. A few publications in scientific journals outline and describe a few individual cases of shingles after COVID-19 vaccinations. However, these studies have either no control group or no appropriate control group.

A widely reported publication about this is a study published in the journal Rheumatology on April 12, 2021, which reported six cases of shingles out of 491 patients with autoimmune inflammatory rheumatic diseases (AIIRD), following vaccination with the COVID-19 Pfizer vaccine. These cases are helpful to document to understand any potential risks of COVID-19 vaccines, particularly for immunosuppressed individuals. However, the study only draws attention to a possible association between mRNA COVID-19 vaccine and herpes zoster. It does not show that the vaccines cause shingles. The shingles outbreak occurring at the same time as the coronavirus outbreak may just be a coincidence, according to early data.

This study is also particularly limited because 1) individuals with AIIRD are at increased risk already of developing shingles, 2) Israel has given at least one dose of Pfizer's two-shot vaccine to more than half the population, and 3) only one of the 6 individuals who developed shingles in the study had received a shingles vaccine.

In order to better understand the association, people with rheumatoid arthritis who hadn’t been vaccinated would also need to be compared as the control group.

Reports have been circulating that COVID-19 vaccines, particularly mRNA COVID-19 vaccines, can cause herpes zoster, also known as shingles. This misplaced belief stems from claims on social media, as well as the misinterpretation of case reports from scientific articles. These false claims have been extrapolated to go as far to say that COVID-19 vaccines can cause herpes and other sexually transmitted infections.

There is currently no evidence to back these claims. While it’s important to continue investigating potential side effects from COVID-19 vaccines, the scientific literature looking into any potential connection so far has not found any evidence that indicates cases of shingles following COVID-19 vaccination is more than a coincidence.

Making claims that this type of coincidence is evidence for a causal association is known as ecological fallacy.