Background Accurate estimates of SARS-CoV-2 infection in different
population groups are important for the health authorities. In Norway,
public infection control measures have successfully curbed the pandemic.
Military training and service are incompatible with these measures, and
therefore stricter infection control measures were necessary in the
Norwegian Armed Forces. We present the measures, and discuss the results
and their value. We report on the seroprevalence of SARS-CoV-2 and the
changes in antibody levels over six weeks. Methods In April 2020, 1170
healthy conscripts (median age 20 years) were enrolled. The infection
control measures included a pre-enrollment telephone interview and
self-imposed quarantine. Questionnaire data and serial SARS-CoV-2 PCR
and serology testing were used to estimate the incidence of confirmed
SARS-CoV-2, describe symptoms and monitor titer levels over a six week
period. Results The seroprevalence of SARS-CoV-2 was 0. 6 %. Only 0. 2
% had a positive PCR for SARS-CoV-2 at the enrollment day. Serological
titer levels increased up to nearly five-fold over the observation
period. Eighteen conscripts reported mild respiratory symptoms during
the 14 days prior to enrollment (all were PCR negative, one had positive
serology), whereas 17 conscripts reported respiratory symptoms and nine
had fever at the day of enrollment (all were PCR and serology negative).
Conclusions The prevalence of SARS-CoV-2 in young adults in Norway is
less than 1%. Testing of asymptomatic conscripts seems of no value in
times of low COVID-19 prevalence. SARS-CoV-2 antibody titer levels
increased substantially over time in youths with mild symptoms.