Moderna's (MRNA.O) Covid-19 vaccine may have a higher risk of heart inflammation in young men than the Pfizer (PFE.N)/BioNTech (22UAy.DE) shot, according to data presented on Tuesday to US Food and Drug Administration advisers weighing its use for those aged 6 to 17.
An FDA official told the expert panel that while the data showed a higher risk for the Moderna shot, the findings were not consistent across various safety databases and were not statistically significant, meaning they might be due to chance.
The overall incidence is relatively rare and the vast majority who suffer the side effect fully recover, but a comparison showed the risk of myocarditis and pericarditis in young males aged 18-39 was 1.1 to 1.5 times higher after the Moderna shot, the FDA said in its presentation, citing data from three US vaccine safety databases.
Data from a US Centers for Disease Control and Prevention database showed 4.41 excess heart inflammation cases per 100,000 who received the Pfizer/BioNTech shot in those aged 18-39 versus 6.27 excess cases per 100,000 for Moderna.
There have long been concerns that the Moderna shot, which is given at a higher dose than the Pfizer/BioNtech shot, may cause myocarditis and pericarditis at higher rates.
Some countries in Europe have limited use of Moderna's vaccine for younger age groups after surveillance suggested it was tied to a higher risk of heart inflammation, and the FDA delayed its review of the Moderna shot to assess the myocarditis risk.
The FDA said data from European and Canadian regulators showed that the risk was 1.7 to 7.3 times higher for Moderna's vaccine than Pfizer's in adolescents and young men.
Outside experts are considering the data before deciding whether to recommend Moderna's vaccine for children and teens aged 6-17 years of age. The Pfizer vaccine is already authorized for children 5 and older.