Assessing Natural Anti-Covid Immunity: Serology, Cellular Immunity

Abstract

It is important to evaluate natural immunity against Covid-19: it is stronger, longer lasting and of better quality than vaccine immunity only humoral (antibody) or cellular adaptive immunity can be assessed; innate immunity is not measurable. Serology is the only routine test, it is the measurement of the antibody level. The measurement of the antibody level leads to an underestimation of the seroprevalence which is already high and above 50% of the population in most countries. The reasons for this underestimation are: The tests are designed against the strain isolated in 2019 in China and the calibration is against convalescent blood collected before June 2020. There is considerable heterogeneity in the commercial tests available. A large percentage of the infected population may have negative serology within months of infection Cellular immunity testing could eliminate these false negatives but it is not routinely applicable and is expensive.