From The Week:

I posed this question to Chelsea Boyd, a research associate in harm reduction at the libertarian R Street Institute with a master’s in epidemiology. “Simply from a logistics perspective, I’m not sure how a large country would manage to process certificate requests and validate test results with any measure of speed, accuracy, or equity,” she said. Something may be feasible in Germany — with a quarter of the United States’ population in a 27th of the territory — but impossible here.

Yet bureaucratic limitations weren’t the only issue Boyd raised. Another is the nature of antibody testing itself, coupled with what we simply don’t know about COVID-19 immunity. Antibody tests don’t “differentiate between a remitted infection and an active infection,” she noted, and home testing (like that planned in Germany) is “generally considered less reliable than lab-confirmed testing.” That’s not to say it’s worthless, only that user error and test precision are real concerns (compare, for example, home pregnancy tests to those done by a doctor or midwife).

Furthermore, though “evidence strongly suggests that after a person recovers from COVID-19 they are immune to reinfection, at least in the short term,” Boyd told me, we don’t know that for certain or if the short term is weeks, months, or years. And immunity certificates “are meaningless,” she continued, “if COVID-19 immunity isn’t complete or lasting.” A certificate system could even become dangerous, Boyd warned, if it were used as a substitute for a “robust” public health response to keep health-care facilities from being overwhelmed and “eventually decrease spread enough that we can go back to using case identification, isolation, and contact tracing as the primary means of preventing subsequent outbreaks.”

Boyd and Eddington both raised another risk of immunity certificates: fraud, whether via faking home test results, as Boyd suggested, or forging or buying black market forgeries of the certificates, as Eddington mentioned. The economic value of an immunity certificate would be enormous, and plenty of people would be desperate enough to lie or pay to get one. Others would deliberately contract a COVID-19 infection with perhaps misplaced confidence that they would quickly recover and be duly certified to go back to work.

None of this is to say mass testing isn’t a vital part of our response to the novel coronavirus. Eddington argued for imitation of the South Korean model, which relied on rapid, widespread testing, and Boyd predicted “antibody testing and confirmed immunity will play some role in every area’s plan to relax social distancing measures.”

Featured Publications