CAMBRIDGE (CBS) – Moderna says a third booster dose of its COVID-19 vaccine will likely be necessary this fall because of the rapid spread of the Delta variant of the coronavirus.

“We believe that increased force of infection resulting from Delta, non-pharmaceutical intervention (NPI) fatigue, and seasonal effects (moving indoors) will lead to an increase of breakthrough infections in vaccinated individuals,” the Cambridge-based company said in a presentation on earnings released Thursday.

In a separate announcement Thursday, Moderna said its vaccine is 93-percent effective against the coronavirus six months after people get the second dose.

But in the earnings presentation, the company said it expects “neutralizing titers will continue to wane and eventually impact vaccine efficacy.” In other words, Moderna admits Delta is a new threat that needs to be monitored carefully and could impact the durability of the vaccine.

“Given this intersection, we believe dose 3 booster will likely be necessary prior to the winter season,” the company said in it’s presentation.

Later it was noted that, “We believe a booster (dose 3) is likely to be necessary this fall, particularly in the face of Delta.”

The booster test doses are 50-micrograms, which is half of Moderna’s 100-microgram standard shot.

Moderna said the clinical data “appears to support” the 50 mcg dose, but they will wait for more data in the “coming weeks” to confirm it.

Tufts Medical Center Epidemiologist Dr. Shira Doron told WBZ-TV she doesn’t think booster shots are needed just yet.

“The question is what was the vaccine for? It was to keep people alive and we don’t need a booster to do that, but we do need to vaccinate the unvaccinated and we do need to vaccinate the whole world and variants will emerge if we don’t focus our efforts on that.”

Dr. Doron also said they are hearing of people going to vaccine clinics and not revealing that they’ve already had two shots and then getting a third. She says she does not recommend doing that.

Moderna is also working on a vaccine that would combine a “COVID-19 variant booster + seasonal flu booster + RSV booster,” all in a single dose.

CBSBoston.com Staff