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Like an exercise regimen that pairs weight lifting with cardio, Crotty explained that these individuals benefit from the combination of quantity and varied quality of the immune response they build. And that could indicate promising signs for boosters.

Scientists are seeking to replicate that strong protection, but without people having to contract COVID-19, as it’s universally agreed that infection is not an optimal immunization course.

Instead, they’re hoping booster doses of vaccines could convey a similar effect.

But timing is key when it comes to additional doses, whichever vaccine is given. Researchers say that exact right interval when immune response has matured -- but before protection begins to wane -- is the ideal target.

\"Our immune system is built to have repeated exposures to the same antigen,\" which will \"substantially\" enhance immune protection, Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center said.

\"PHOTO:
Matt Rourke/AP
PHOTO: A syringe is prepared with the Pfizer COVID-19 vaccine at a clinic at the Reading Area Community College in Reading, Pa., Sept. 14, 2021.
>

Experts are still gleaning what exactly is the benefit of this enhanced immunity, though it’s not novel to coronavirus.

Flu vaccines, for example, are “boosted\" for children receiving them, while adults receive one dose, yearly.

\"This is because of hybrid immunity. Adults have already been exposed to influenza and have primed their immune response,\" Goepfert said.

\"What we have seen is that waiting six months does mount a better immune response later,\" he added. \"It seems that our immune system likes to rest and develop antibodies, and then mount a stronger response when it sees the same pathogen again later on.\"

There is not enough data yet to say if the mix-and-match approach of priming one vaccine and boosting with another is going to offer better or more durable protection. But while the jury remains out, experts are hopeful.

\"The mix-and-match approach in vaccine administration has been studied for decades, but unfortunately not for COVID,\" Barouch said. \"while larger studies are underway, it is best to stay with the same vaccine for the booster, if approved.\"

Lily Nedda Dastmalchi, D.O., M.A., is a physician and cardiology fellow at Temple University Hospital, and a contributor to the ABC News Medical Unit.

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