Serology testing for antibodies induced by Covid-19 may indicate past exposure without past infection
Robert A. Michaels Toxicological health risk assessor, RAM TRAC Corporation, Schenectady, New York https://science.sciencemag.org/content/368/6495/1060/tab-e-letters
(18 June 2020)
Krammer and Simon (Science 5 June) appropriately highlight uncertainties about SARS-CoV-2, which causes Covid-19 disease, and the potential of serological testing to reduce them. The authors cite Wu, et a/. (2020) for reporting on the viral genome. However, they state without evidence that serological assays “measure the antibody responses induced by SARS-CoV-2 infection (past but not current infections).”
Serology assays do test for antibodies, but antibodies often are produced by mechanisms other than infection. Ideally they are produced by vaccination, and ideally vaccines do not produce infection. Lots of people vaccinated against polio have antibodies; they do not typically have a (current or past) polio infection.
Antibodies generically indicate past exposure, not necessarily past infection. Most exposures to SARS-CoV-2, especially outdoors, involve aged, not fresh virus particles. The viruses precipitate out of the air in minutes to hours, and die within hours to days of landing on surfaces. These aged viruses may be weakened (‘attenuated’), inactivated (‘dead’), or fragmented.
Such compromised viruses may predominate human exposure and even stimulate antibody production. They also may be useful for vaccine development. Ultimately, serology testing alone might neither record Covid-19 infections, nor quantify Covid-19
infection prevalence.
Determining Covid-19 infectivity is complicated. The infection rate might be determined best via simultaneous serology testing for antibodies and diagnostic testing for viral RNA. That strategy would improve prediction of infection rates under relaxed distancing scenarios for re-opening regional economies.
Literature Cited F. Wu et a/., Nature 579, 225 (2020)
Competing Interests: None declared.
Publication citation
Michaels, RA. Serology testing for antibodies induced by Covid-19 may indicate past exposure without past infection. Science Magazine, e-Letter, online: https://science.sciencemag.org/content/368/6495/1060/tab-e-letters, 18 June 2020;