SARS-CoV-2 Seroprevalence in Germany

Area of Science:

• Epidemiology
• Infectious Disease Surveillance
• Public Health

Background:

• Official SARS-CoV-2 infection data in Germany primarily relies on public health office reports.
• These reports may underestimate the true prevalence due to asymptomatic and mild infections.

Purpose of the Study:

• To determine SARS-CoV-2 seroprevalence across Germany during the pandemic.
• To estimate the missed-case rate and infection fatality rate (IFR).
• To analyze factors associated with seropositivity.

Main Methods:

• Sequential, multilocal seroprevalence study (MuSPAD) with random participant recruitment in seven German districts.
• Two blood sample tests per participant, 3-5 months apart, from July 2020 onward.
• Analysis included missed-case rate, IFR, associations with demographics, and self-reported test results.

Main Results:

• Seroprevalence among unvaccinated individuals rose from 1.3-2.8% (July-Dec 2020) to 4.1-13.1% (Feb-May 2021).
• Surveillance detection ratio (SDR) varied by district, generally declining over time.
• Lower education correlated with higher seropositivity; smoking with lower seropositivity. IFR ranged from 0.3% to 2.4%.

Conclusions:

• Seroprevalence was low post-first wave but increased substantially during subsequent waves.
• The missed-case rate demonstrated a downward trend throughout the study period.