Germany’s low SARS-CoV-2 seroprevalence confirms effective containment in 2020: Results of the nationwide RKI-SOEP study

Abstract

Pre-vaccine SARS-CoV-2 seroprevalence data from Germany are scarce outside hotspots, and socioeconomic disparities remained largely unexplored. The nationwide RKI-SOEP study with 15,122 adult participants investigated seroprevalence and testing in a supplementary wave of the Socio-Economic-Panel conducted predominantly in October-November 2020. Self-collected oral-nasal swabs were PCR-positive in 0.4% and Euroimmun anti-SARS-CoV-2-S1-IgG ELISA from dry capillary blood in 1.3% (95% CI 0.9-1.7%, population-weighted, corrected for sensitivity=0.811, specificity=0.997). Seroprevalence was 1.7% (95% CI 1.2-2.3%) when additionally adjusting for antibody decay. Overall infection prevalence including self-reports was 2.1%. We estimate 45% (95% CI 21-60%) undetected cases and analyses suggest lower detection in socioeconomically deprived districts. Prior SARS-CoV-2 testing was reported by 18% from the lower educational group compared to 25% and 26% from the medium and high educational group (p<0.0001). Symptom-triggered test frequency was similar across educational groups. However, routine testing was more common in low-educated adults, whereas travel-related testing and testing after contact with an infected person was more common in highly educated groups. In conclusion, pre-vaccine SARS-CoV-2-seroprevalence in Germany was very low. Notified cases appear to capture more than half of infections but may underestimate infections in lower socioeconomic groups. These data confirm the successful containment strategy of Germany until winter 2020.

Estimating the distribution of COVID-19-susceptible, -recovered, and -vaccinated individuals in Germany up to April 2022

“…, which is in line with results informed by seroprevalence data for Germany in 2020 [18]. Furthermore, with a 97.5th percentile of 4.7, the distribution is broad enough to account for occasional high under-ascertainment ratios that have been observed locally [10,17,18]. For infants, ascertainment is expected to be lower than for other age groups [21], which is why we double under-ascertainment ratios for this age group.…”

“…, which is in line with results informed by seroprevalence data for Germany in 2020 [18]. Furthermore, with a 97.5th percentile of 4.7, the distribution is broad enough to account for occasional high under-ascertainment ratios that have been observed locally [10,17,18].…”

“…For instance, the reported uncertainties (quartile ranges) are heavily determined by the choice of distribution of 𝑎 𝜙 . The distribution we chose has a median value of 𝑄 2 [𝑎 𝜙 ] = 1.7, which is slightly lower than what was observed in 2020 [18]. Moreover, the lower distribution bound of min(𝑎 𝜙 ) = 1 might be rather low, as such a value would mean that every infection has been reported, which is unlikely.…”

“…To estimate the number of people that have been in contact with either virus or vaccine, one might simply summate the number of vaccinations and the number of reported infections. However, doing so ignores the fact that (a) a considerable number of vaccinated people have suffered from additional breakthrough infections (taking into account both asymptomatic and symptomatic infections herein) [12], (b) a substantial number of previously infected people have chosen to be vaccinated in accordance with national recommendations [13–15], (c) some individuals have suffered from multiple infections [16], and (d) the exact extent of the total number of infections as compared to the reported number of infections is unknown because (i) asymptomatic infections are less likely to be identified and reported in the national surveillance system and (ii) underascertainment varies regionally [17, 18]. In order to estimate the overlap between the vaccinated and recovered subpopulations, one may assume that the probability of any recovered individual to be vaccinated is proportional to the probability of any individual to be vaccinated.…”

Analysis of Fatality Impact and Seroprevalence Surveys in a Community Sustaining a SARS-CoV-2 Superspreading Event

“…Overall, in seroprevalence studies where only a tiny portion of the population is selected for serological testing (e.g. typically 0.01-1% in nation-wide surveys 38 ) one should remain cautious, as errors in counting deaths, seroprevalence, and other sources of uncertainty may have an larger impact.…”