Levels of SARS-CoV-2 population exposure are considerably higher than suggested by seroprevalence surveys

Chen, S.; Flegg, J. A.; White, L. J.; Aguas, R.

Accurate knowledge of levels of prior population exposure will inform preparedness plans for subsequent SARS-CoV-2 epidemic waves and vaccination strategies. Serological studies can be used to estimate levels of past exposure and thus position populations in their epidemic timeline. To circumvent biases introduced by decaying antibody titers over time, population exposure estimation methods should account for seroreversion. Here, we present a new method that combines multiple datasets (serology, mortality, and virus positivity ratios) to estimate seroreversion time and infection fatality ratios and simultaneously infer population exposure levels. The results indicate that the average time to seroreversion is five months, meaning that true exposure may be more than double the current seroprevalence levels reported for several regions of England.