Risk factors associated with occurrence of COVID-19 among household persons exposed to patients with confirmed COVID-19 in Qingdao Municipal, China

Transbound Emerg Dis. 2021 Mar;68(2):782-788. doi: 10.1111/tbed.13743. Epub 2020 Aug 30.


Tracing and isolation of close contacts is used to control outbreaks of coronavirus disease 2019 (COVID-19) in China. However, risk factors associated with the occurrence of COVID-19 among close contacts have not been well described. A total of 106 household contacts were included in this study, of whom 19 developed into COVID-19 cases, and the secondary attack rate was 17.9%. Multivariable analysis showed that increasing risk of occurrence of COVID-19 among household contacts was associated with female index patients (adjusted hazard ratio [aHR] = 3.84, 95% CI = 1.07-13.78), critical disease index patients (aHR = 7.58, 95% CI = 1.66-34.66), effective contact duration with index patients > 2 days (aHR = 4.21, 95% CI = 1.29-13.73), and effective contact duration > 11 days (aHR = 17.88, 95% CI = 3.26-98.01). The sex and disease severity of index patients with COVID-19 and longer effective contact duration with patients with confirmed COVID-19 could help epidemiologists to identify potential COVID-19 cases among household contacts at an early stage.

Keywords: COVID-19; SARS-CoV-2; close contacts; household contacts; risk factor.

MeSH terms

  • Adult
  • COVID-19 / epidemiology*
  • COVID-19 / transmission
  • China / epidemiology
  • Cohort Studies
  • Contact Tracing
  • Disease Outbreaks*
  • Disease Transmission, Infectious
  • Family Characteristics*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Prospective Studies
  • Risk Factors
  • SARS-CoV-2*