The fast-spreading delta variant is so contagious, it’s exposed weaknesses in vaccine protection and changed the outlook for ending the pandemic, Moderna President Stephen Hoge said late Wednesday.

He said that Delta “just so great at infecting people, and reproducing that it raises standards on what good vaccines must be.” “It’s actually shown some of the weaknesses that [vaccines] have earlier than you might expect.”

Moderna shared Wednesday a new analysis from its phase three study that showed the incidence of breakthrough Covid cases, which occur in fully vaccinated people, was less frequent in a group of trial participants who were recently inoculated, suggesting the Covid vaccine’s protection wanes over time.

The company released a press statement saying that 88 breakthrough cases were identified out of 11431 individuals who had been vaccinated from December to March. This compares with 162 cases among the 14,746 trial participants, which was vaccinated during July and October last year.

The breakthrough cases are not all delta’s fault, Hoge said. According to Hoge, he thinks that the Covid cases seen in people who have been vaccinated are due to vaccine protection decreasing over time as well as the high transmissible variant.

He said that the delta variant was not an immune escape variant and added that it is “weakening” our defenses at a time of declining vaccine protection.

“It’s likely what led to phase three results, which we’re currently seeing. It’s lead to the real-world efficacy difference that has been reported this summer between vaccines,” he stated.

Hoge claimed that Covid booster shots can be widely used based on the drugmaker’s most recent results. These have not yet been peer reviewed.

Hoge stated that “it’s the reason for getting ahead of the problem, and boost.”

He made these comments ahead of Friday’s Food and Drug Administration vaccination advisory committee meeting. This group will consist of outside experts who will debate whether sufficient data is available to enable widespread distribution of booster shot across the U.S.

The group, called the agency’s Vaccines and Related Biological Products Advisory Committee, will debate administering third doses of Pfizer and BioNTech‘s vaccine as federal health regulators say they need more time to review Moderna’s application for extra doses.

Moderna’s future booster shot plans could be affected by how the meeting unfolds.

The science community currently has a split opinion on booster shots.

Biden’s administration stated that it will begin providing booster shots for the general population as soon as possible, subject to FDA authorization. The move is part of President Joe Biden‘s broader plan to confront a higher number of Covid cases fueled by the fast-spreading delta variant.