The Centers for Disease Control and Prevention is considering approving Moderna and Johnson & Johnson vaccine as boosters.
And if it follows the Food and Drug Administration's lead, it could allow the three vaccines to be mixed and matched.
With nearly 60% of the population fully vaccinated against COVID-19, health leaders are making it clear: we are nowhere near herd immunity.
"The issue with the delta variant, for example, is it was more transmissible than previous variants and therefore herd immunity needed to be higher," said Dr. Philip Chan, an infectious disease specialist at The Miriam Hospital and a medical consultant with the Rhode Island Department of Health.
He said an approval of the two remaining COVID-19 vaccines as boosters promises to get vaccines to tens of millions more Americans who would benefit -- those 65 and older and those at high risk for complications of this coronavirus.
"It does appear these vaccines wane over time," said Chan. "For example, the Pfizer vaccine we know at say six months."
Which, he said, highlights the importance of that booster.
For those who are fully vaccinated with Moderna, the recommendations look to be six months after the second dose for those deemed at high risk, and that booster is only a half dose.
The FDA is also recommending all those who got the one dose Johnson & Johnson shot -- no matter their age -- get a booster shot at least two months after the initial shot.
"Based on available data, the J&J vaccine, while a very good vaccine, has been associated with slightly more serious side effect risk of clotting compared to the other vaccine," said Chan, who went on to say the mixing and matching of vaccines would be most applicable to those people.
For those only partially vaccinated with one of the MRNAs, Chan said it's best to stick with that one, and leave the mixing and matching for the boosters. Your best defense, he said, is getting vaccinated in the first place.