Background Accurate estimates of SARS-CoV-2 seroprevalence are crucial for the implementation of effective public health measures, but are currently largely lacking in regions with low infection rates. This is further complicated by inadequate test performance of many widely used serological assays. We therefore aimed to assess SARS-CoV-2 seroprevalence in a region with low COVID-19 burden, especially focusing on neutralizing antibodies that presumably constitute a major component of acquired immunity. Methods We invited all individuals who were enrolled in the Rhineland Study, an ongoing community-based prospective cohort study in people aged 30 years and above in the city of Bonn, Germany (N=5427). Between April 24th and June 30th, 2020, 4771 (88%) of these individuals participated in the serosurvey. Anti-SARS-CoV-2 IgG levels were measured using an ELISA assay, and all positive or borderline results were subsequently examined through both a recombinant immunofluorescent assay and a plaque reduction neutralisation test (PRNT). Findings Seroprevalence was 0.97% (95% CI: 0.72-1.30) by ELISA and 0.36% (95% CI: 0.21-0.61) by PRNT, and did not vary with either age or sex. All PRNT+ individuals reported having experienced at least one symptom (odds ratio (OR) of PRNT+ for each additional symptom: 1.12 (95% CI: 1.04-1.21)). Apart from living in a household with a SARS-CoV-2 confirmed or suspected person, a recent history of reduced taste or smell, fever, chills/hot flashes, pain while breathing, pain in arms/legs, as well as muscle pain and weakness were significantly associated with the presence of neutralizing antibodies in those with mild to moderate infection (ORs 3.44 to 9.97, all p<0.018). Interpretation Our findings indicate a relatively low SARS-CoV-2 seroprevalence in Bonn, Germany (until June 30th, 2020), with neutralizing antibodies detectable in only one third of those with a positive immunoassay result, implying that almost the entire population in this region remains susceptible to SARS-CoV-2 infection.
Seroprevalence and correlates of SARS-CoV-2 neutralizing antibodies: Results from a population-based study in Bonn, Germany