Canadian health officials said on Friday data suggests reported cases of rare heart inflammation were relatively higher after Moderna's COVID-19 vaccine compared with the Pfizer/BioNTech shots.
The data also indicated heart inflammation occurs more often in adolescents and adults under 30 years of age, and more often in males.
The statement from the Public Health Agency of Canada said the majority of the affected individuals experienced relatively mild illness and recovered quickly.
The risk of cardiac complications, including heart inflammation, has been shown to be substantially increased following COVID-19 infections, with the risks higher after the infection than after vaccination, according to the statement.
The benefits of mRNA shots in preventing COVID-19 continue to outweigh the risks, regulators in the United States, EU and the World Health Organization have said.