Those who have received the Moderna COVID-19 mRNA vaccine are less likely to experience "breakthrough" COVID-19 cases, compared to recipients of the Pfizer-BioNTech mRNA vaccine, finds a new study.

The research, published in the Journal of the American Medical Association, also found those who received the Moderna vaccine were less likely to be hospitalised, compared to recipients of the Pfizer-BioNTech vaccine.

"Breakthrough COVID infections, hospitalisation and mortality associated with the Delta variant were compared between recipients of Moderna mRNA vaccine and recipients of Pfizer mRNA vaccine while considering patient characteristics and the varying time since vaccination," said researcher Rong Xu from Case Western Reserve University.

A vaccine breakthrough infection occurs when a person becomes infected after being fully vaccinated (receiving two doses of the mRNA vaccine), according to the Centers for Disease Control and Prevention in the US.

For the study, which examined breakthrough SARS-CoV-2 infections, hospitalisations and death rates when the Delta variant was predominant, the team analysed electronic health records of more than 637,000 fully vaccinated patients.

Incidents of breakthrough infections were included if the person had not been previously infected with COVID-19 or had received a booster vaccination. The findings showed that the monthly incidence rate of breakthrough cases was higher in those who received the Pfizer BioNTech vaccine, compared to the Moderna vaccine. No significant difference was observed in mortality rates between those who received the Moderna vaccine and Pfizer- BioNTech vaccine.