Seroprevalence of SARS-CoV-2-Specific IgG Antibodies Among Adults Living in Connecticut: Post-Infection Prevalence (PIP) Study

Am J Med. 2021 Apr;134(4):526-534.e11. doi: 10.1016/j.amjmed.2020.09.024. Epub 2020 Oct 29.


Background: A seroprevalence study can estimate the percentage of people with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies in the general population; however, most existing reports have used a convenience sample, which may bias their estimates.

Methods: We sought a representative sample of Connecticut residents, ages ≥18 years and residing in noncongregate settings, who completed a survey between June 4 and June 23, 2020, and underwent serology testing for SARS-CoV-2-specific immunoglobulin G (IgG) antibodies between June 10 and July 29, 2020. We also oversampled non-Hispanic black and Hispanic subpopulations. We estimated the seroprevalence of SARS-CoV-2-specific IgG antibodies and the prevalence of symptomatic illness and self-reported adherence to risk-mitigation behaviors among this population.

Results: Of the 567 respondents (mean age 50 [± 17] years; 53% women; 75% non-Hispanic white individuals) included at the state level, 23 respondents tested positive for SARS-CoV-2-specific antibodies, resulting in weighted seroprevalence of 4.0 (90% confidence interval [CI] 2.0-6.0). The weighted seroprevalence for the oversampled non-Hispanic black and Hispanic populations was 6.4% (90% CI 0.9-11.9) and 19.9% (90% CI 13.2-26.6), respectively. The majority of respondents at the state level reported following risk-mitigation behaviors: 73% avoided public places, 75% avoided gatherings of families or friends, and 97% wore a facemask, at least part of the time.

Conclusions: These estimates indicate that the vast majority of people in Connecticut lack antibodies against SARS-CoV-2, and there is variation by race and ethnicity. There is a need for continued adherence to risk-mitigation behaviors among Connecticut residents to prevent resurgence of COVID-19 in this region.

Keywords: Antibodies; COVID-19; Connecticut; SARS-CoV-2; Seroprevalence.

MeSH terms

  • Antibodies, Viral / blood*
  • Attitude to Health / ethnology
  • COVID-19 Serological Testing* / methods
  • COVID-19 Serological Testing* / statistics & numerical data
  • COVID-19* / diagnosis
  • COVID-19* / epidemiology
  • COVID-19* / immunology
  • COVID-19* / psychology
  • Connecticut / epidemiology
  • Ethnicity
  • Female
  • Humans
  • Immunoglobulin G / blood*
  • Male
  • Middle Aged
  • Needs Assessment
  • Prevalence
  • Risk Reduction Behavior*
  • SARS-CoV-2 / isolation & purification
  • Seroepidemiologic Studies


  • Antibodies, Viral
  • Immunoglobulin G