Infection rate and factors affecting close contacts of COVID‐19 cases: A systematic review

Abstract

Objective Contact tracing plays an essential role in mitigating the impact of an epidemic. During the COVID‐19 pandemic, studies of those who have been in close contact with confirmed cases offer critical insights to understand the epidemiological characteristics of SARS‐CoV‐2 better. This study conducts a meta‐analysis of existing studies' infection rates and affecting factors. Methods We searched PubMed, Web of Science and CNKI from the inception to April 30 2022 to identify systematic reviews. Two reviewers independently extracted the data and assessed risk of bias. Meta‐analyses were conducted to calculate pooled estimates by using Stata/SE 15.1 software. Results There were 47 studies in the meta‐analysis. Among COVID‐19 close contacts, older age (RR = 1.94, 95% CI: 1.70, 2.21), contacts in households (RR = 2.83, 95% CI: 2.20, 3.65), and people in close contact with symptomatic infections (RR = 3.62, 95% CI: 1.88, 6.96) were associated with higher infection rates. Conclusion On average, each primary infection corresponded to 5.8 close contacts. Among COVID‐19 close contacts, older age and contacts in households were associated with higher infection rates, and people in close contact with symptomatic infections had three times higher risk of infection compared to people in close contact with asymptomatic infections. In general, there are significantly more studies from China about close contacts, and the infection rate among close contacts was lower compared to other countries.

Infection rate among close contacts of patients with coronavirus disease in Japan: a descriptive study and literature review

“…The different ORs in the analysis confirming the impact of the stratification (duration) factor also suggest that the infection rate among close contacts changed. Among COVID-19 close contacts, the elderly and household contacts have higher infection rates, and those with close contact with symptomatic COVID-19 patients reported a 3-fold higher risk of infection than those with close contact with asymptomatic COVID-19 patients [16]. In addition, close contacts who have frequent contact with COVID-19 patients and those exposed to COVID-19 patients with symptoms of coughing are at increased risk of infection [8].…”

Close contacts of xenograft recipients: Ethical considerations due to risk of xenozoonosis

“…There are notable parallels and precedents for guidelines tailored to individuals who come into close contact with certain patient groups, such as vaccination recommendations specific to close contacts of immunocompromised individuals and guidance around close contact with individuals with known SARS-CoV-2 infections. 18,19 It is similarly vital to consider whether and how close contacts should be informed of, and asked to provide consent or assent for the risks of xenotransplantation. We broadly describe five options: Option D: The scope of risk to individuals beyond the recipient necessitates consideration beyond just close contacts, but anyone who could be deemed a bystander with a risk of potential exposure.…”

“…There are notable parallels and precedents for guidelines tailored to individuals who come into close contact with certain patient groups, such as vaccination recommendations specific to close contacts of immunocompromised individuals and guidance around close contact with individuals with known SARS‐CoV‐2 infections 18,19 . It is similarly vital to consider whether and how close contacts should be informed of, and asked to provide consent or assent for the risks of xenotransplantation.…”

A network meta-analysis of risk factors of infection among close contacts of COVID-19

“…For example, the SARs for living together range from 3.83 % to 68.2 % [ 20 , 21 ], the SARs for social activities such as dining range from 1.02 % to 15.29 % [ 22 , 23 ], a difference of more than ten times. And there are also differences in the combined effects of some meta-analysis reports, for example, some studies believe that family members have a high risk of infection [ 12 , 24 ], while others believe that eating together has a high risk of infection [ 25 ]. Additionally, the understanding and evidence are lacking on the order in which different risk factors contribute to infection.…”