No Link Between mRNA COVID-19 Vaccinations and Shingles Flare-Ups: Study

By Matthew Phelan

December 15, 2021

NEW YORK (Reuters Health) - New research helps dispel concerns that mRNA-based COVID-19 vaccination could be associated with an increased risk of herpes zoster reactivation.

"There have been published case reports, as well as a lot of anecdotal reports, of herpes zoster post-COVID vaccination," Dr. Nisha Acharya, an ophthalmologist at the University of California, San Francisco, told Reuters Health via email.

"I have seen and also heard about a number of patients with herpes zoster ophthalmicus (reactivation of varicella zoster virus in the eye), and my colleagues have as well," said Dr. Acharya, who was not involved in the new study, but has researched herpes zoster and vaccination. "However, this could all be reporting bias where there is heightened concern on events post-COVID vaccination."

For the study, published in the Journal of the American Academy of Dermatology, researchers used data from the TriNetX Analytics Network, which aggregates the health records of approximately 70 million patients across 63 healthcare organizations in the U.S.

Dr. Morgan Birabaharan of the University of California, San Diego, and colleagues identified more than 1.3 million individuals who had received at least one dose of an mRNA COVID-19 vaccine. The mean age in the cohort was 55 years, 57% were female, 14% Black, 65% white, 11% Hispanic or Latino, and 6% Asian.

The researchers used propensity matching to pair this cohort with controls based on factors known to impact shingles risk, including age, sex, race, ethnicity, HIV, malignancy, the patient's use of antineoplastics or immunosuppressants, and receipt of a shingles vaccine. The control population was assembled from TriNetX data on persons diagnosed with acne, viral warts, melanocytic nevi, dry skin, lipoma, skin cysts, or seborrheic keratosis who had received no reported COVID-19 vaccination.

A case of herpes zoster was classified as related to mRNA COVID-19 vaccination if symptoms occurred within 28 days of either a first or second dose of the vaccine.

"The 28-day interval was chosen to be in accordance with the Vaccine Adverse Event Reporting System (VAERS) safety assessment reporting interval (7-day intervals)," Dr. Birabaharan told Reuters Health by email.

The four-week period also helped the researchers "explore latency of reactivation following vaccination," he added.

Dr. Birabaharan and his colleagues divided their controls into a "historical cohort" whose respective diagnoses fell within the timeframe of the pandemic, but prior to availability of COVID-19 vaccines, as well as a "contemporary cohort" whose diagnoses followed the vaccine roll-out.

"It would have been unfair to assess rates of VZV (varicella zoster virus) reactivation among the vaccinated cohort against earlier years, because of the likely higher burden of shingles related to stress from COVID-19," Dr. Birabaharan explained.

The historical cohort included 555,256 patients and was paired with an equally sized group of people who had received an mRNA COVID-19 vaccine. The contemporary cohort and its parallel mRNA COVID-19 vaccination cohort each contained 359,789 patients.

The study found no significant difference in the risk of reemerging herpes zoster after vaccination when compared with either the historical cohort (relative risk, 0.91; 95% confidence interval, 0.81 to 1.01) or the contemporary cohort (RR, 0.98; 95% confidence interval, 0.87 to 1.11).

"It will be important to investigate this research question in other databases with other comparator groups," Dr. Acharya said. "Propensity scoring helps to balance the groups, but it is not foolproof, and there may be unidentified confounders which could be affecting the results."

As one example, she noted that it was "not clear from the report what the rate of vaccination was in their cohort" and whether it aligned with the Center for Disease Control and Prevention's estimates from that same time period.

The study had no commercial support and the researchers declare no conflicts of interest.

SOURCE: Journal of the American Academy of Dermatology, online November 22, 2021.