Moderna says Covid-19 vaccine protection wanes

New data from Moderna Inc's large Covid-19 vaccine trial shows that the protection it offers wanes over time, supporting the case for booster doses, the company said in a news release on Wednesday.

"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 at a conference call with investors.

Hoge did not project how many of the cases would be severe, but said some would require hospitalization.

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 Inc and German partner BioNTech SE.

Experts said the difference is 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.