"If it works like protein-based vaccines for other diseases, it may create a group of special cells called memory B cells and memory T cells. These cells will retain information about the coronavirus for years or even decades, enabling a quick counterattack in response to a new infection."

"Novavax reported that their United Kingdom trial determined an efficacy rate of 96 percent against the original coronavirus. But in South Africa, where volunteers were exposed to the variant B.1.351, the efficacy was only 49 percent."

https://www.nytimes.com/interactive/2020/heal...ccine.html