Seroprevalence of antibodies against SARS-CoV-2 in the adult population during the pre-vaccination period, Norway, winter 2020/21.

Content Provider	Europe PMC
Author	Anda, Erik Eik Braaten, Tonje Borch, Kristin Benjaminsen Nøst, Therese Haugdahl Chen, Sairah L F Lukic, Marko Lund, Eiliv Forland, Frode Leon, David A Winje, Brita Askeland Kran, Anne-Marte Bakken Kalager, Mette Johansen, Fridtjof Lund Sandanger, Torkjel M
Copyright Year	2022
Abstract	BackgroundSince March 2020, 440 million people worldwide have been diagnosed with COVID-19, but the true number of infections with SARS-CoV-2 is higher. SARS-CoV-2 antibody seroprevalence can add crucial epidemiological information about population infection dynamics.AimTo provide a large population-based SARS-CoV-2 seroprevalence survey from Norway; we estimated SARS-CoV-2 seroprevalence before introduction of vaccines and described its distribution across demographic groups.MethodsIn this population-based cross-sectional study, a total of 110,000 people aged 16 years or older were randomly selected during November–December 2020 and invited to complete a questionnaire and provide a dried blood spot (DBS) sample.ResultsThe response rate was 30% (31,458/104,637); compliance rate for return of DBS samples was 88% (27,700/31,458). National weighted and adjusted seroprevalence was 0.9% (95% CI (confidence interval): 0.7–1.0). Seroprevalence was highest among those aged 16–19 years (1.9%; 95% CI: 0.9–2.9), those born outside the Nordic countries 1.4% (95% CI: 1.0–1.9), and in the counties of Oslo 1.7% (95% CI: 1.2–2.2) and Vestland 1.4% (95% CI: 0.9–1.8). The ratio of SARS-CoV-2 seroprevalence (0.9%) to cumulative incidence of virologically detected cases by mid-December 2020 (0.8%) was slightly above one. SARS-CoV-2 seroprevalence was low before introduction of vaccines in Norway and was comparable to virologically detected cases, indicating that most cases in the first 10 months of the pandemic were detected.ConclusionFindings suggest that preventive measures including contact tracing have been effective, people complied with physical distancing recommendations, and local efforts to contain outbreaks have been essential.
ISSN	1025496X
Journal	Eurosurveillance
Volume Number	27
PubMed Central reference number	PMC8973017
Issue Number	13
PubMed reference number	35362405
e-ISSN	15607917
DOI	10.2807/1560-7917.ES.2022.27.13.2100376
Language	English
Publisher	European Centre for Disease Prevention and Control (ECDC)
Publisher Date	2022-03-01
Access Restriction	Open
Rights License	This is an open-access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0) Licence. You may share and adapt the material, but must give appropriate credit to the source, provide a link to the licence, and indicate if changes were made. This article is copyright of the authors or their affiliated institutions, 2022.
Subject Keyword	Seroprevalence SARS-CoV-2 Covid-19 Norway contact tracing cumulative incidence
Content Type	Text
Resource Type	Article
Subject	Virology Public Health, Environmental and Occupational Health Epidemiology