Seroconversion in household members of COVID-19 outpatients
Authors: Rebecca J Cox, Karl A Brokstad, Florian Krammer, Nina Langeland, Bjørn Blomberg, Kanika Kuwelker, Sarah Lartey, Dagrun Waag Linchausen, Kristin GI Mohn, Francisco Gomez Real, Amit Bansal, Geir Bredholt, Anders Madsen, Therese Bredholt Onanygo, Mai Chi Trieu, Juha Vahokoski, Fan Zhou
Journal: The Lancet Infectious Diseases (2020)

We read with interest the Article by Qifang Bi and colleagues,1Bi Q Wu Y Mei S et al.Epidemiology and transmission of COVID-19 in 391 cases and 1286 of their close contacts in Shenzhen, China: a retrospective cohort study.Lancet Infect Dis. 2020; (published online April 27.)https://doi.org/10.1016/S1473-3099(20)30287-5Summary Full Text Full Text PDF PubMed Scopus (1082) Google Scholar in which they reported a household secondary attack rate, as detected by repeated RT-PCR tests, of approximately 11%. We have found substantially higher attacks rates in western Norway through detection of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first case of COVID-19 in Norway was identified in Bergen on Feb 28, 2020, before the outbreak was declared a pandemic, allowing rigorous testing of suspected cases before and during the rise in confirmed cases. All suspected COVID-19 cases in the peak period between Feb 28 and April 4 were referred to the Bergen municipality emergency room for centralised evaluation and testing according to a strict exposure likelihood algorithm, allowing an overview of the early virus spread in the population. If a family was exposed, only the index case was tested for SARS-CoV-2 infection. Both cases and household members were tested for specific antibodies to the receptor binding domain of SARS-CoV-2, as described by Stadlbauer and colleagues,2Amanat F Stadlbauer D Strohmeier S et al.A serological assay to detect SARS-CoV-2 seroconversion in humans.Nat Med. 2020; (published online May 12.)https://doi.org/10.1038/s41591-020-0913-5Crossref PubMed Scopus (1162) Google Scholar at 6 weeks after the index patient tested positive by RT-PCR. Of 158 cases, 125 (79%) tested positive for antibodies and 12 (8%) were defined as borderline. In 77 household members, 24 (31%) tested positive and two (3%) were borderline. Our results show that detection of seroconversion might provide a more accurate picture of attack rates in households than intermittent RT-PCR testing. FK reports that an assay used to screen for seroconversion was developed in his laboratory and that Mount Sinai has filed patent applications to protect that assay, has licensed its use for several companies, and is commercialising the assay. All other authors declare no competing interests. Download .pdf (.12 MB) Help with pdf files Supplementary appendix Epidemiology and transmission of COVID-19 in 391 cases and 1286 of their close contacts in Shenzhen, China: a retrospective cohort studyOur data on cases as well as their infected and uninfected close contacts provide key insights into the epidemiology of SARS-CoV-2. This analysis shows that isolation and contact tracing reduce the time during which cases are infectious in the community, thereby reducing the R. The overall impact of isolation and contact tracing, however, is uncertain and highly dependent on the number of asymptomatic cases. Moreover, children are at a similar risk of infection to the general population, although less likely to have severe symptoms; hence they should be considered in analyses of transmission and control. Full-Text PDF Correction to Lancet Infect Dis 2020; published online June 15. https://doi.org/10.1016/S1473-3099(20)30466-7Cox RJ, Brokstad KA, Krammer F, Langeland N. Seroconversion in household members of COVID-19 outpatients. Lancet Infect Dis 2020; published online June 15. https://doi.org/10.1016/S1473-3099(20)30466-7—The appendix of this Correspondence has been corrected as of June 25, 2020. Full-Text PDF