SARS-CoV-2 Period Seroprevalence and Related Factors, Hillsborough County, Florida, USA, October 2020-March 2021

Emerg Infect Dis. 2022 Mar;28(3):556-563. doi: 10.3201/eid2803.211495. Epub 2022 Jan 26.


Estimating the actual extent of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic is challenging because virus test positivity data undercount the actual number and proportion of persons infected. SARS-CoV-2 seroprevalence is a marker of past SARS-CoV-2 infection regardless of presence or severity of symptoms and therefore is a robust biomarker of infection period prevalence. We estimated SARS-CoV-2 seroprevalence among residents of Hillsborough County, Florida, USA, to determine factors independently associated with SARS-CoV-2 antibody status overall and among asymptomatic antibody-positive persons. Among 867 participants, SARS-CoV-2 period prevalence (October 2020-March 2021) was 19.5% (asymptomatic seroprevalence was 8%). Seroprevalence was 2-fold higher than reported SARS-CoV-2 virus test positivity. Factors related to social distancing (e.g., essential worker status, not practicing social distancing, contact with a virus-positive person, and length of contact exposure time) were consistently associated with seroprevalence but did not differ by time since suspected or known infection (<6 months vs. >6 months).

Keywords: COVID-19; Florida; Hillsborough County; SARS-CoV-2; United States; coronavirus disease; respiratory infections; seroepidemiologic studies; seroprevalence; serosurvey; severe acute respiratory syndrome coronavirus 2; vaccine-preventable diseases; viruses; zoonoses.

MeSH terms

  • Antibodies, Viral
  • COVID-19*
  • Florida / epidemiology
  • Humans
  • Pandemics
  • SARS-CoV-2*
  • Seroepidemiologic Studies


  • Antibodies, Viral