COVID-19 vaccines don’t cause herpes infections; a possible association with the reactivation of herpes zoster in patients with rheumatic diseases remains unconfirmed

CLAIM
“Herpes infections may be a side effect of a COVID-19 vaccine”
DETAILS
Inaccurate: The study cited by the New York Post article didn't show that the Pfizer-BioNTech COVID-19 vaccine caused new herpes infections. Instead, it suggested that vaccination might reactivate pre-existing varicella-herpes virus from past chickenpox infections in some people with weakened immune systems.
Inadequate support: Regarding claims made on Facebook/Instagram: Patients with weakened immune systems, including rheumatic patients, are at higher risk of developing shingles. The study didn't include a group of unvaccinated rheumatic patients and, therefore, couldn't establish whether shingles in these patients were causally linked to the COVID-19 vaccine or the result of being immunosuppressed.
KEY TAKE AWAY
Herpes zoster (shingles) is a viral infection caused by the varicella-zoster virus that also causes chickenpox. This virus doesn't cause other types of herpes, such as genital herpes. Only people who had chickenpox in the past can develop shingles, which result from a reactivation of pre-existing virus in the body. One study reported six cases of shingles in patients with rheumatic diseases after receiving the Pfizer-BioNTech COVID-19 vaccine, suggesting that the vaccine might trigger viral reactivation in these patients. However, the study wasn't designed to establish a causal association between shingles and the vaccine because it didn't include a group of unvaccinated rheumatic patients.

FULL CLAIM: “Herpes infections may be a side effect of a COVID-19 vaccine”; “now people are getting herpes from the [COVID-19] shot”

REVIEW


On 20 April 2021, the New York Post published this article claiming that “herpes infections may be a side effect of a COVID-19 vaccine”. News outlets like Fox News echoed the New York Post article, which received more than 25,000 interactions on Facebook, according to the social media analytics tool Crowdtangle.

The article reported the results from a study by Furer et al. published a week earlier in the scientific journal Rheumatology[1]. This study aimed to collect information about the safety of COVID-19 vaccines in patients with autoimmune inflammatory rheumatic diseases, a group of conditions that cause the immune system to attack the joints, muscles, bones, and organs. Although patients with rheumatic diseases might be more likely to suffer complications from COVID-19[2], there is no safety data of the COVID-19 vaccines for this specific population because clinical trials excluded these patients.

Furer et al. monitored adverse events in 491 patients with rheumatic diseases and 99 control participants within six weeks after receiving the Pfizer-BioNTech COVID-19 vaccine. The authors reported that six patients with rheumatic diseases developed herpes zoster following vaccination, compared to none in the control group.

The New York Post article correctly stated that these results didn’t prove a causal link between the COVID-19 vaccine and herpes zoster. However, it claimed that the vaccine might cause “herpes infections” as a side effect. As we explain below, this claim is inaccurate because herpes zoster can only occur in people who were previously infected. This claim misled many social media users into erroneously interpreting that COVID-19 vaccines caused herpes infections. Posts containing such claims and sharing the New York Post article (see examples here and here) went viral on Facebook and Instagram, receiving hundreds of thousands of interactions altogether.

Herpes zoster, commonly known as shingles, is a viral infection caused by the varicella-zoster virus that also causes chickenpox. When a person infected with chickenpox recovers, the virus remains dormant in the nerve tissues. However, in some cases, the virus can reactivate many years later as the painful skin rash that characterizes shingles. Stress, depression, and conditions that weaken the immune system can also trigger viral reactivation. Patients with rheumatic diseases often receive treatments such as glucocorticoids that weaken their immune response, making them more likely to have infections in general and also to develop shingles[3].

In other words, the condition isn’t due to a new infection, as the New York Post claimed, because the study detected shingles in these patients, which are the result of virus reactivation, or pre-existing virus from past infections. If researchers had observed new infections, then the patients would have developed chickenpox instead, which is a different illness. But this wasn’t the case. Therefore, claiming that the study observed “herpes infection” is inaccurate.

It is possible that the vaccines might trigger the reactivation of the virus in some people who already had the virus from previous chickenpox infections. However, the study didn’t include a group of unvaccinated rheumatic patients, and therefore couldn’t establish whether the cases of shingles were associated to the COVID-19 vaccine or to the fact that the patients were immunosuppressed, contrary to what has been claimed in social media posts sharing the New York Post article. The authors of the study stated:

“The study design is not structured to determine a causal relationship between [Covid-19] vaccination and HZ [herpes zoster].”

The New York Post article also didn’t explain that the varicella-zoster virus is different from those that cause genital herpes, specifically herpes simplex viruses type 1 and 2. This lack of context led some social media users to share the article claiming that COVID-19 vaccines caused genital herpes infections that could be sexually transmitted (examples here and here).

This claim is also inaccurate. Although they belong to the same family of herpesviruses, varicella-zoster virus and herpes simplex viruses are different and cause different diseases. The varicella-zoster virus causes chickenpox and shingles but not genital herpes, as the posts claimed.

The best way to prevent shingles is with the chickenpox vaccine, which is more than 90% effective at preventing chickenpox infection and thus protects people from developing shingles later in life. In the U.S., there is also one vaccine against shingles available that prevents up to 97% of the cases in older adults who had chickenpox in the past.

While shingles outbreaks haven’t been reported in COVID-19 vaccine clinical trials or ongoing vaccinations, some studies suggest that they might occur in COVID-19 patients[4-6]. There isn’t enough scientific evidence to establish a causal relationship between both conditions. However, if COVID-19 indeed increased the risk of shingles outbreaks, COVID-19 vaccines would be beneficial for preventing reactivation of the varicella-herpes virus in patients at high risk.

In summary, COVID-19 vaccines cannot cause genital herpes infections, and there is currently also no clear evidence that they increase the risk of developing shingles. Still, cases of viral reactivation following vaccination have been reported in the past[7], and this possibility cannot be excluded, particularly in people with weakened immune systems or those who are receiving treatments that weaken their immune system.

REFERENCES

   

Published on: 26 Apr 2021 | Editor:

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