Serological assays for SARS-CoV-2 can guide reintroduction of workforce if used with caution

With several high-quality serological assays for SARS-CoV-2 now available, the key challenge in using them to help people return to "normal life," write Florian Krammer and Viviana Simon in this Perspective, will be to apply them in a strategic manner - one that considers their unique sensitivity and specificity levels, acknowledges the questions they don't yet answer, and more.

Serological assays - which detect SARS-CoV-2-specific antibodies in recovered peoples' blood - will be important to informing questions around the prevalence of the virus in certain populations and of immunity to it. It has been proposed that individuals with robust antibody responses in these assays could safely return to work, for example. However, though several assays have received emergency use authorization, these tools still don't fully answer questions about whether all infected individuals mount a robust antibody response, whether antibody titers to the virus correlate with protection from reinfection, and how long any such protection would last. It is "a matter of urgency" to conduct studies that better answer these questions, Krammer and Simon write.

Otherwise, they say, "decisions about deploying the workforce may be based on incomplete information and guided by incorrect assumptions." Krammer and Simon describe ways to use these tools best. For example, each one has variable levels of sensitivity (how many true positives are detected) and specificity (the proportion of false positives). Studies of the results of serosurveys should account for this, and also for the estimated prevalence of infections in the study population, they say. As well, it is important to consider these tools' more politically charged applications (i.e., for "immune passports," for those who show immunity through one test or another). Krammer and Simon acknowledge the promise of serological assays but also note that any results generated from them in the immediate future should be interpreted with caution.