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 on a conference call with investors.

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