RALEIGH, N.C. (WNCN) – COVID-19 vaccine maker Moderna now says people who already got vaccinated may need a third dose by the end of the year.
“We get influenza vaccines every year. So this is not so unusual,” said Dr. David Weber, a professor of medicine, pediatrics, and epidemiology at UNC-Chapel Hill.
The introduction of the delta variant changed a lot, including how experts think about the current vaccines.
“This is people responding appropriately to things that have changed over time,” Weber said.
He said there’s more evidence now that the immunocompromised may benefit from an extra dose. It’s an opinion echoed by the top medical advisor to the White House Dr. Anthony Fauci.
“It’s extremely important for us to move to get those individuals boosters. And we are now working on that to be implemented as quickly as possible,” Fauci said on Thursday.
Weber said some immunocompromised people never built up protection from their initial doses.
“Which is very, very unusual in a person with a normal function immune system. And those that do have an immune response, sometimes the antibody level is much lower,” Weber said.
Moderna expects their efficacy for everyone to start decreasing after six months. They said clinical data shows a booster with the original formula — but half the dosing of their initial doses — is helpful.
Pfizer says their studies show protection from the Delta variant in people 18 to 55 was five times greater after a third dose. People ages 65 to 85 saw 11 times greater protection after a third dose.
“The fact that the virus has changed somewhat and the immunity may be a little decreased, I do want to say the vaccines work very well,” said Weber.
Weber says talk of the impact of the delta variant on vaccines shouldn’t deter people from getting their shot.
“They’re even more of a reason to run out and get one right away,” he said.
Mixing and matching doses
Scientists at Oxford University in the United Kingdom have tested combinations of the two-dose COVID-19 vaccines made by AstraZeneca, Moderna, Novavax and Pfizer-BioNTech.
The study found combining AstraZeneca and Pfizer shot was safe and effective. Additionally, it also found that combination resulted in a higher antibody response.
That might be because mixing and matching different types of vaccines can often produce a stronger immune response, said Lawrence Young, a virologist at the University of Warwick in the United Kingdom.
Mixing and matching is still not approved in the U.S. The National Institutes of Health has initiated a trial to study mixing and matching for boosters. Fully vaccinated participants will receive booster doses from a different maker. Results are expected at the end of summer.