JMIR Publications

ABSTRACT

Background:

Contact tracing (CT), the process of identifying and managing contacts of infected cases, is one public health and social measure that may reduce the spread of infectious diseases. While previous systematic reviews of CT exist, a comprehensive review of both the effectiveness and potential unintended consequences has not been undertaken to our knowledge. Understanding of effective CT strategies could help governments and health authorities prepare effectively for emergency epidemic or pandemic situations.

Objective:

To systematically review evidence about CT across infectious diseases with epidemic or pandemic potential.

Methods:

We searched six bibliographic databases (MEDLINE, Embase, Global Health, CINAHL Ultimate, Cochrane, Scopus) between November 29th to 3rd December 2024, with supplementary citation searching. We sought human studies comparing CT to interventions with no CT or other forms of CT, delivered in the community, in pre-specified diseases of epidemic or pandemic potential. We included studies with any measure of disease transmission, related healthcare use, or unintended consequences of CT and prioritised studies with concurrent comparators. All screening, data extraction and critical appraisal was performed in duplicate. Due to substantial heterogeneity, a narrative synthesis was performed. This review was informed by meetings with a patient and public involvement and engagement group.

Results:

After de-duplication, 12,816 titles and abstracts were screened, with 198 records assessed for eligibility at full text. Five additional studies were found through supplementary searching. Finally, 88 reports (of 86 studies) were included, of which 57 reports of 55 studies were prioritised. Two main routes of transmission were represented: respiratory (tuberculosis (n=15 studies), Covid-19 (n=5 studies)) and bloodborne/sexually transmitted infections (STIs) (n=35 studies, of which 13 were in HIV, and 22 were bacterial/parasitic infections). Evidence was highly heterogeneous, and more than half of studies had notable methodological limitations. While there was no difference between CT and comparator interventions for most outcomes, there was some evidence of reductions in disease prevalence in tuberculosis, and for provider-initiated CT to be superior to patient-led approaches in STIs. Only two studies reported measures of unintended consequences.

Conclusions:

We found inconsistent evidence for the effectiveness of CT, focused primarily on tuberculosis and on contrasts between provider-initiated CT and patient-led referral in STIs and HIV. High heterogeneity in study design precluded any clear assertions as to optimal strategies for CT, including with respect to relevant subgroups. Future work should consider generalisability of CT mechanisms across contexts, including by route of transmission, and from the Global South; and a more thorough account of unintended consequences. Clinical Trial: CRD42025628278