New data from Moderna's large COVID-19 vaccine trial shows the protection it offers wanes over time, supporting the case for booster doses, the company says.
"This is only one estimate, but we do believe this means as you look toward the fall and winter, at minimum we expect the estimated impact of waning immunity would be 600,000 additional cases of COVID-19," Moderna president Stephen Hoge said on a conference call with investors on Wednesday.
Hoge did not project how many of the cases would be severe but said some would require hospitalisation.
The data stands in stark contrast with data from several recent studies that suggested Moderna's vaccine protection lasts longer than a similar shot from Pfizer and German partner BioNTech SE.
Experts said the difference was likely due to Moderna's higher dose of messenger RNA (mRNA) and the slightly longer interval between the first and second shots.
Both vaccines proved to be exceedingly effective at preventing illness in their large phase III studies.
Wednesday's analysis, however, showed higher rates of infection among people vaccinated roughly 13 months ago compared with those vaccinated roughly eight months ago.
The study period was from July-August, when Delta was the predominant strain. It has yet to undergo peer review.
Moderna on September 1 submitted its application to the US Food and Drug Administration seeking authorisation for a booster shot.
Hoge said data from its booster studies showed the vaccine could increase neutralising antibodies to levels even higher than were seen after the second dose.
"We believe this will reduce COVID-19 cases," he said. "We also believe that a third dose of mRNA-1273 has a chance of significantly extending immunity throughout much of next year as we attempt to end the pandemic."
Australian Associated Press