Because scientists have yet to prove that just because someone has recovered from COVID-19 and produced antibodies to the virus does not mean they are protected from contracting it a second time, researchers still do not have a clear picture of what immunity looks like (Source: “Immunity to the Coronavirus Remains a Mystery. Scientists are Trying to Crack the Case,” STAT, June 11, 2020).
Experts anticipate an initial coronavirus infection will lend people some level of immunity for some amount of time. They still do not know what combination of antibodies, cells, and other markers in a person’s blood will signify that protection. Determining those “correlates of protection” is crucial both so individuals can know if they are again at risk, and so researchers can understand how well potential vaccines work, how long they last, and how to accelerate their development.
“What you would like is to have some blood measure that serves as a correlate of that protective efficacy or immunity,” said Sarah Fortune, the chair of immunology and infectious diseases at Harvard’s T.H. Chan School of Public Health. “Which sounds like it’s simple, but it’s much more complicated than you’d think.”