Moderna study: Recently vaccinated have stronger protection from breakthrough COVID-19

COVID-19 boosters could be ready by September

President Joe Biden announced on Wednesday plans to get boosters to fully vaccinated Americans as soon as the week of Sept. 20.

LOS ANGELES - New data released by Moderna on Wednesday found that people who were vaccinated more recently had greater protection from breakthrough COVID-19 cases caused by concerning variants of the coronavirus.

Moderna said its data supports the benefit of a booster dose of its COVID-19 vaccine, pointing to evidence of waning protection over time.

In a vaccine effectiveness study conducted with Kaiser Permanente Southern California (KPSC), researchers found that participants who were vaccinated more recently (median 8 months after first dose) had a lower risk of contracting a breakthrough COVID-19 infection than those who were vaccinated last year (median 13 months after first dose).

"It is promising to see clinical and real-world evidence adding to the growing body of data on the effectiveness of the Moderna COVID-19 vaccine," said Stéphane Bancel, chief executive officer of Moderna.

Moderna has asked the Food and Drug Administration to allow a booster dose of its vaccine.

Researchers compared about 14,000 people in Moderna’s 2020 vaccine study who had gotten a first dose about a year ago with another 11,000 vaccinated last winter, roughly eight months ago. As delta surged in July and August, Moderna concluded the more recently vaccinated group had a 36% lower rate of "breakthrough" infections compared with those vaccinated longer ago.

The new Moderna data comes as influential government advisers are scheduled to debate Friday if there’s enough proof that a booster dose of Pfizer's COVID-19 vaccine is safe and effective — the first step toward deciding which Americans need one and when.

Last month, Pfizer-BioNTech announced they are seeking approval from U.S. regulators for the third dose of their COVID-19 vaccine, called Comirnaty.

The FDA authorized last month an additional COVID-19 booster vaccine for people who have compromised immune systems.

The FDA on Wednesday posted much of the evidence its advisory panel will consider. The agency struck a decidedly neutral tone on the rationale for boosters — an unusual and careful approach that's all the more striking after President Joe Biden and his top health advisers trumpeted a booster campaign they hoped to begin next week.

Pfizer’s argument: While protection against severe disease is holding strong in the U.S., immunity against milder infection wanes somewhere around six to eight months after the second dose. The company gave an extra dose to 306 people at that point and recorded levels of virus-fighting antibodies threefold higher than after the earlier shots.

If the FDA decides the extra shot does those two things, then the Centers for Disease Control and Prevention will have to decide who should get another dose. The CDC has scheduled a meeting of its own advisers for next week and has signaled it is considering a booster for certain people — such as older adults, nursing home residents and front-line health workers — rather than the general population.

The CDC says real-world data show protection against severe illness, hospitalizations and deaths is holding strong. But in one recent study, protection against infection slipped as the delta variant hit: It was 91% in the spring but 78% in June and July. The CDC also has seen a hint that for people 75 and older, protection against hospitalizations slightly declined in the summer.

The Associated Press contributed to this story.