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368(6495):1060-1, https://science.sciencemag.org/content/368/6495/1060, doi:
10.1126/Science.abc1227, online 15 May, print 5 June 2020
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
(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 al. (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
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
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.
F. Wu et al., Nature 579, 225 (2020)
Competing Interests: None declared.