Sept. 16, 2021 – New data from vaccine maker Moderna appears to support the argument for COVID-19 booster shots —showing waning effectiveness months after the first dose.

Specifically, the company data shows that people who received a first shot of Moderna’s mRNA vaccine a median of 13 months ago are more likely to experience a breakthrough infection compared to individuals who received a first shot a median of 8 months ago.

The findings come from Moderna’s ongoing phase III clinical trial, which the FDA considered in granting emergency use authorization to Moderna's vaccine. In the initial stage of the trial, people were randomly assigned to receive the company's mRNA vaccine or a placebo.

Trial participants who were immunized more recently were 36% less likely to experience a breakthrough infection

The trial data shows 88 breakthrough cases of COVID-19 among 11,431 participants vaccinated from December 2020 to March 2021.

But there were 162 breakthrough cases among 14,746 people vaccinated from July to October 2020.

The findings were posted as a preprint to the medRxiv server and have not yet been peer reviewed.

"The increased risk of breakthrough infections in … study participants who were vaccinated last year compared to more recently illustrates the impact of waning immunity and supports the need for a booster to maintain high levels of protection," Moderna CEO Stéphane Bancel said in a statement.

An FDA advisory committee is meeting Friday to look at the available evidence on boosters to help the agency decide whether the additional shots are warranted.

There is still a lot of debate in the medical community about the need for boosters. U.S. doctors and nurses are divided about the need for them and about how the country should prioritize its vaccine supplies, according to a WebMD/Medscape poll of more than 1,700 clinicians t from Aug. 25 to Sept. 6.