People who receive Moderna's COVID-19 vaccine may have a higher risk of developing chronic hives, according to a study conducted by researchers in Denmark. The Danish Medicines Agency reviewed data from Denmark and the European Union and found a safety signal for chronic hives and Moderna's shot. Out of 360 reported cases of chronic hives following the Moderna or Pfizer-BioNTech vaccine, 58 were deemed probably caused by vaccination and 228 were determined to be possibly caused by the vaccination. Most of the cases were reported by patients, doctors, or pharmaceutical companies.
The study found that the risk of developing chronic hives was three times higher for Moderna recipients compared to the general population. The researchers also stratified the risk by gender and age and found that young men had the highest risk, which was 5.2 times higher than the background rate. Most cases of chronic hives occurred between 7 to 13 days following vaccination.
The results of the study validate a safety signal for chronic hives associated with the COVID-19 vaccines. However, the Danish Medicines Agency stated that additional studies are required to confirm a connection and that scientists believe the cases may be caused by the vaccine's impact on the immune system.
The cases of chronic hives started being reported after the introduction of COVID-19 vaccines, and Norway reported a safety signal for chronic hives in late 2021. Although the Danish Medicines Agency initially concluded that the cases were not strong enough to establish a safety signal, further investigation prompted by data from the county's compensation system for vaccine injuries led to new results. The review was strengthened by gaining access to medical records from the compensation system.
Based on these findings, the European Medicines Agency's Committee for Medicinal Products for Human Use has recommended updating the labeling for Moderna's shot to include chronic hives as a possible side effect. Non-chronic hives is already listed as a possible side effect. The change in labeling will be implemented if approved by the European Union Commission.
Previous studies have also reported cases of chronic hives following COVID-19 vaccination. In 2022, U.S. researchers reported three new cases of chronic hives after Pfizer and Moderna vaccination. Swiss researchers in 2023 analyzed new cases of chronic hives after Pfizer and Moderna vaccination and suggested a link between a booster dose of Moderna's vaccine and the health problem. Another case series in January reported seven patients who developed chronic urticaria within weeks of Moderna vaccination, indicating a potential correlation between the shot and the issue.
It is worth noting that hives have also been associated with COVID-19 itself, but researchers are unsure whether there is a causal link.
In conclusion, the study conducted in Denmark found a higher risk of developing chronic hives among individuals who received Moderna's COVID-19 vaccine. The results validate a safety signal for chronic hives associated with the vaccine, although further studies are needed to confirm the connection. The findings have led to recommendations for updating the vaccine's labeling to include chronic hives as a possible side effect.
