What to know about 'original antigenic sin' and fall COVID boosters

With new COVID variant-specific booster shots set to roll out in the coming week, vaccine scientists argue that more research is needed to understand how a person's early

immune response -- either through vaccination or infection itself -- may impact future protection against a constantly evolving virus. The body learns its best defensive

moves during its first encounter with a virus, according to experts. However, once a virus evolves, the immune system is slower to respond. That is a phenomenon called

"original antigenic sin," or "immune imprinting." Scientists say that despite nearly three years of living amid pandemic there are unanswered questions. For example:

What's the best way to maximize protection through vaccination? What vaccine formula would deliver the broadest immune coverage? How often should people receive booster shots?

The answers would help public health authorities decide future vaccination strategies such as the vaccine’s formula and when doses are administered. What is

original antigenic sin or immunological imprinting? "There's a theory that our immunological response to the first exposure to a virus may sort of imprint your immune system,"

said John Brownstein, an ABC News contributor and chief innovation officer at Boston Children's Hospital. The human immune system's best playbook is against an invader it

already knows, experts say. But the virus has continued to shape-shift, evolving into new variants that are still recognizable, but slightly different from predecessors.