The omicron variant of SARS-CoV-2 drove broadly increased seroprevalence in a public university setting

Omicron is the comparatively most transmissible and contagious variant of
severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). We conducted
a seroprevalence study spring 2022, to investigate the seroprevalence of
SARS-CoV-2 antibodies among individuals aged 18 years and older after the
Omicron outbreak. The seroprevalence of anti-receptor binding domain (RBD)
antibodies was found to be 96.3% (95% CI 95.2-97.2%) compared to 88.2%
(95% CI 86.1-90%) in our previous serosurvey. For anti-nucleocapsid (NC)
antibodies, the seroprevalence was 39.1% (95% CI 36.6-41.7%) compared to
19.7% (95% CI 17.5-22.2%) earlier. Individuals that experienced
breakthrough infections exhibited the highest levels of anti-RBD
antibodies. Additionally, saliva samples showed promise as a potential
diagnostic biofluid for measuring antibody levels, as they exhibited a
strong agreement with the data obtained from serum samples. The near
doubling of anti-NC reactivity, a proxy for history of infection, reflects
the contagiousness of the omicron variant, but may also have been
influenced by a more relaxed approach to precautions in the spring of
2022. Serosurveys repeated at regular intervals monitor the trend of
infections in the community, delineate the geographical spread of the
infection, and may guide containment measures in communities, and prompt
response to future outbreaks.