Updated: February 1, 2021
Definition: Contact tracing is a process through which we can break chains of COVID-19 transmission, connect people to care, and identify clusters or outbreaks.
A comprehensive contact tracing program includes: conducting case investigation, identifying known exposed contacts, providing support for both positive cases and exposed individuals to safely isolate or quarantine until no longer infectious, and connecting unvaccinated individuals with vaccination resources.
Each person who is newly diagnosed with COVID-19 as a “case” is interviewed to enumerate their close contacts, e.g. those who have been within six feet for 15+ minutes over a 24-hour period. Those people who are identified as close contacts are notified and entered into a care management system, so that they can:
- Stay in safe quarantine according to CDC guidelines, supported by resources to protect themselves and their families
- Be tested for COVID
- Be monitored for symptoms
This process is the prospective component of contact tracing. Another important aspect of case investigation is called “source investigation”, or understanding where the person may have been infected with COVID-19. This is also called retrospective tracing. It is an important part of identifying clusters and is discussed further in Outbreak Response.
Contact tracing is not new for Departments of Public Health in the US. Local health departments have historically conducted contact tracing for other diseases, such as tuberculosis and sexually transmitted infections, but additional support is essential to manage the volume of cases and contacts associated with the novel threat of COVID-19. COVID-19 is also rapidly transmissible and can cause large outbreaks and move through communities quickly, introducing a higher degree of time pressure to testing and tracing than with some other conditions.
Contact tracing is a core public health tool used to respond to infectious disease outbreaks. It was identified early on as a way to combat COVID 19. Contact tracing, supplemented with community protection strategies, widespread testing, supported isolation and quarantine, and vaccination are the essential components of an effective pandemic response and of the broader public health toolkit for epidemic control and care delivery.
Previous contact tracing efforts:
- Contact tracing helped prevent Ebola from spreading in other West African countries during the 2014-2016 outbreak. Studies describe the importance of contact tracing in also identifying gaps that can be addressed for future response.
- Contact tracing was one of several interventions that helped control the SARS epidemic in 2003.
- Contact tracing was a core component of smallpox eradication and is frequently used for HIV, STIs, and tuberculosis.
Since people can transmit COVID before or without symptoms, contact tracing combined with quarantine is most effective.
Evidence supporting contact tracing in COVID-19 includes:
- South Korea, Singapore, New Zealand, Taiwan, and Iceland implemented contact tracing programs early on, helping to slow their epidemics.
- In England, due to a data systems error, some areas implemented contact tracing for cases sooner than others. Places with more timely contact tracing had fewer cases and deaths, providing "strong quasi-experimental evidence for the effectiveness of contact tracing".
- A modeling study published in the Lancet shows that even if other interventions (e.g. physical distancing) reduce the reproductive number, contact tracing can help reduce it further. The higher the percentage of contacts traced, the more effective contact tracing is.
Contact tracing is not only a purely epidemiological exercise to stop the spread of COVID-19, but also a care exercise that connects cases and contacts to social and material support. Given the potential logistical, emotional, and financial difficulties of quarantining or isolating for several days, effective contact tracing programs must also be able to connect cases and contacts to food, housing, medicine or other needs that arise over the quarantine and isolation period, like diapers or rent. Without contact tracing programs that can provide social support, people will have to choose between quarantining to stop the spread or continuing with their daily lives, thus perpetuating the pandemic. The inability to quarantine or isolate without direct support disproportionately affects poorer people and communities of color. Incorporating social support mechanisms into contact tracing programs also introduces the possibility of connecting cases and contacts to longer term support programs. This could include long-term enrollment in benefits programs for food, rental assistance or housing, or other resources in their community.
Effective contact tracing programs are guided by four core elements:
- Technical expertise: Effective contact tracing programs that successfully reach cases and contacts require epidemiological knowledge, logistical capacity, clinical support guidelines, robust training and mentorship programs, and program management expertise. Programs should be set up by or in conjunction with public health departments.
- Adequate Staffing: Without adequate staffing and flexibility, contact tracing programs will be unable to flex up and down as the course of the disease changes. A nimble, trained workforce is necessary to create an effective contact tracing program.
- Leadership: In order to implement a contact tracing program at the state or local level, effective government leadership is necessary to champion and manage the program, combat misinformation, build community buy-in, and properly finance tracing efforts.
- Equity agenda: Equity must be built into any COVID-19 contact tracing program to combat the systemic racism that puts Black, Latinx, and Native American populations at a higher risk of contracting the virus and suffering poor outcomes including death; these populations also have higher needs for social support in order to safely quarantine or isolate. Contact tracing programs must address these needs.
- Building a robust COVID-19 contact tracing program requires high-level political support and significant resources.
- COVID-19 contact tracing programs should be integrated within or in close partnership with public health departments who know the context of a region and have been doing this work for years. Contact tracing programs should amplify the existing work of local public health departments rather than centering themselves as the primary source of knowledge.
- Strong leadership and buy-in at both the senior policymaker and programmatic levels is necessary to a successful contact tracing program. Without buy-in and political will at the highest level, contact tracing programs will often fail to achieve public buy-in or meet funding needs. Strong technical and operational leadership at the program level is needed to guide rapid decision-making about the evolving demands on CT programs.
- Contact tracing programs should be well integrated within a state or local jurisdiction’s larger public health response to COVID-19, with strong operational integration and strategic alignment with testing, mitigation policy, supported isolation/quarantine and vaccine rollout efforts.
- Clear definition of roles, responsibilities and decision rights are essential within complex partnership structures supporting contact tracing; a regular review and adaptation of governance arrangements is essential to keep up with rapidly evolving epidemic dynamics and partner ecosystems.
An overview of the contract tracing process can be found here.
Effective contact tracing programs include 6 pillars. Some programs include all pillars within a central program, others rely on close partnership with separate workstreams:
- Testing – Testing should be widespread and decentralized. A successful and timely contact tracing program relies on tight coordination with testing in order to quickly contact anyone who has tested positive for COVID-19 and to refer contacts for testing.
- Case Investigation is the first step in the process after an individual is diagnosed with COVID-19, Case investigation involves interviewing a newly diagnosed person with COVID-19 to enumerate their contacts, ask about exposure details, monitor their symptoms over time, and ensure ability to safely isolate throughout their illness and provide connections to social support.
- Contact Tracing – After cases identify their contacts, contact tracing involves contacting and interviewing those people identified as exposed contacts through case investigation, and monitoring their symptoms, recommending testing, ensuring their ability to safely isolate throughout quarantine and provide connections to social support.Contacts of positive cases should all be referred to testing.
- Safe Isolation/Quarantine and Care Coordination – In order to successfully isolate/quarantine, CT programs need a coordinated approach to care and social support. Cases and contacts should be screened for social needs during case investigation and contact tracing. Some will require support to safely isolate or quarantine, and programs should mobilize or refer to different social resources including food, housing, transportation, economic support, and mental health and addiction resources.
- Outbreak Investigation – As case investigators uncover sources of exposure through source investigation, contact tracing programs are often the first source of information that a cluster may exist. This can trigger further investigation of the cluster and the outbreak response.
- Vaccination Resources -- COVID-19 identifies pockets of unvaccinated individuals, spreading more easily through unvaccinated populations than those that are vaccinated. By coupling contact tracing with vaccination resources, individualized education is provided to unvaccinated cases and contacts, followed by their connection to vaccination resources if willing. This also helps to prevent future outbreaks and severe disease.
Workforce considerations are described below.
Contact tracers and case investigators are expected to provide a number of services to cases and contacts, including health education on COVID-19; collection of demographic, clinical and exposure information; isolation and quarantine advising; and resource assessment.
- Education – What is COVID-19? How is it spread? What are the symptoms? How can I keep myself and my community safe and healthy?
- Epidemiological Data Collection – Demographic information; clinical information (symptoms, hospitalizations, etc.); exposure information (to identify clusters/multiple exposures); contacts; resource assessment
- Advising on Isolation/Quarantine – Importance of isolation for positive cases; importance of testing/quarantine for contacts; regular follow up and monitoring of symptoms; eventual clearing of people from isolation/quarantine
- Assessment for and Connection to Social Needs – Resource assessment during initial intake; continued assessment during follow up calls; liaising with community partners/care resource coordinators to arrange for resource delivery
Contact tracing includes definitive workflows between all pillars of the COVID response, including testing, treatment, and social support. This contact tracing workflow (page 13) can serve as a model for contact tracing programs creating their own workflows.
Care resource coordination (CRC) is the process of identifying the needs and providing the social, material, and other supports needed to allow cases and contacts to safely isolate or quarantine. Social determinants of health and disparities in health outcomes are exacerbated by the fragmented social support landscape in the U.S. and care resource coordination is a must-have to address this problem. Many cases and contacts cannot isolate or quarantine without support.
CRC work is needed because:
- Isolation (cases) and quarantine (contacts) break the chain of COVID-19 transmission.
- For cases and contacts to isolate and quarantine for 7-14+ days, support systems need to be in place to allow for everyone to quarantine and isolate safely and effectively. Without ensuring that everyone can quarantine and isolate safely, people may be forced to choose between meeting basic needs and quarantining, thereby perpetuating the pandemic.
- CRC work is essential to address health-related social needs and social determinants of health that directly impact individual health outcomes and population health.
Tool: PIH guide on the Components of CRC Programs
- Case investigators and contact tracers should complete an initial needs identification for all cases and contacts.
- Anyone with support needs should be referred to a care resource coordinator and a more detailed needs assessment is conducted.
- CRCs then refer to or provide resources, using warm handoffs and ensuring linkage, in order to support cases or contacts to isolate/quarantine safely. CRCs also help connect individuals to those who can link them to long term benefits if needed.
- Regular follow-up is required to assure additional resources are provided when necessary and symptoms are monitored.
- Screening for social support should be done early and often. Screening should start at testing sites and support should be offered throughout quarantine and isolation at regular intervals. All contact tracing staff should be trained to ask these questions in a non-threatening and culturally appropriate way as well as understand the variety of the types of support people may need.
- CRCs should have local experience and work closely with local partners in order to properly connect cases and contacts with the necessary resources. Diverse language abilities are necessary to reach everyone who may be infected.
- Establish clear referral protocols and lists of social support resources. Incorporate screening questions into contact tracing scripts. Ensure contact tracers and case investigators are trained on requirements for isolation/quarantine, common social needs, specific needs assessment scripts, and how to refer patients to a CRC.
- The overarching goal of care resource coordination is linkage to care, but linkage assumes supply. Creative solutions are required to ensure sufficient referral pathways, including adaptive systems to facilitate referrals between CRCs and community based organizations and updated resource databases organized geographically and thematically.
- Flag potential clusters for outbreak investigations. These clusters often identify pockets of unvaccinated individuals, who can then be connected with education, testing, and vaccination resources.
There are three primary roles within a contact tracing program: case investigators, contact tracers, and care resource coordinators.
- Case investigators engage with newly diagnosed COVID-19 patients, explain diagnosis and facilitate safe isolation; offer assistance; identify people they may have exposed to the virus (contacts); collect key information about the person; identify where the person may have been exposed and if they could be part of a cluster.
- Contact tracers engage with the contacts of people diagnosed with COVID-19; explain their risk of infection and of transmitting the disease; assess symptoms; explain and facilitate safe quarantine; assess support needs; collect key information about the person.
- Care resource coordinators engage with COVID-19 patients and their contacts to understand their resource needs to safely quarantine and isolate; connect them to essential material, financial, and social supports.
Programs should strive to combine the case investigator and contact tracer roles into one cross-trained role. This is for two major reasons: (1) to build a nimble workforce that can withstand large fluctuations in cases and contacts as the pandemic ebbs and flows and (2) to prepare employees for inevitable household transmission that requires them to speak to cases and contacts in the same phone call.
Support structures are necessary to manage the workforce of case investigators, contact tracers, and care resource coordinators, promoting productivity and wellbeing as well as improving program metrics and design.
- Management and Leadership Team: Responsible for oversight and accountability of the program, as well as troubleshooting. Consists of program leadership, responsible for implementation & design, data, strategy, policy, communications, HR, clinical, and coordination with the government and DPH. Should continuously track program metrics to improve program efficacy.
- For a contact tracing program to properly respond to an evolving pandemic and manage ongoing programmatic issues, a strong workforce management team must lead the program.
- Training Team: Responsible for training all new CIs/CTs/CRCs and offering continued education for all employees. Training programs should be nimble and tightly connected to implementation updates.
- Mentors and Peer Support: Given the numerous changing protocols needed in an adaptive CT program, mentors should be continuously available for questions and training of all employees. Peer support programs should be created to offer emotional assistance to employees given the taxing nature of the work.
- A nimble workforce that can fluctuate in size depending on the course of the pandemic is necessary for a program to be effective. The number of contact tracers and case investigators needed will vary, depending on:
- The number of new positive tests (cases)
- The number of contacts per case
- The average duration for each initial case investigation and contact tracing call
- The number of follow up calls per case and contact, and their average duration
- The responsibilities for outbreak investigation and response and linking with businesses or other places where larger exposures may have occurred
- Workforce estimation tools can be useful to estimate how many CTs/CIs/CRCs are needed at a given time
- Partners In Health and the Analysis Group created a workforce quantification tool to model the exact number of contact tracers and case investigators needed based on the epidemiological curve of the disease
- Engage and reinforce existing community health workforce members and cadres, including Community Health Workers, and engage FQHCs as key staffing partners where possible.
- Prioritize hiring from hardest-hit and most vulnerable communities; ensure recruiting and workforce partners have clear accountability for equity and diversity in hiring.
- Prioritize hiring of staff with diverse language capacities to address the diverse language needs of your constituency.
- For call center-based contact tracing programs, recruiting contact tracers with basic to moderate tech skills will increase the speed of training.
- The program should clearly communicate to recruits the evolving nature of the program based on the spread of the infectious disease and the resulting contract length -- a need for flexibility should be a key component of recruiting.
- Essential to rapidly respond to hotspots and outbreaks
- Depending on local financing and governance (home-rules vs. more centralized approach to public health), options for how to ramp up surge staffing vary; approaches include:
- Hire a centralized surge workforce to be deployed upon request to local departments, or operate virtual call centers with full statewide coverage
- Provide grant funding to local health departments to hire and manage surge staff locally
- Contract local CBOs to provide local health department staff with surge support
- Contact tracing communications campaigns should be hyperlocal with connections to local leaders and influencers.
- Building trust and sharing knowledge are the most important goals of any communications program.
- Information should be accessible to everyone in a community – extensive multi-media campaigns, broad coalitions of community organizations, and engagement in representative languages are needed.
- Information should be thoughtfully placed in relevant parts of the process, meaning the places people will likely go before being called by a case investigator if they do test positive (e.g. clinical officers, testing sites, etc.).
- Generate awareness about contact tracing.
- Dispel misinformation by pointing the public to official and comprehensive sources of verified facts.
- Rebuild trust in the public healthcare system among communities that have been historically marginalized.
- Destigmatize COVID-19 by ensuring cases and contacts feel safe when they are contacted and are comfortable sharing their contacts.
- Communicate that contact tracers are calling to help, connect people to medical services and social supports; they are not authority figures seeking to get them in trouble or affecting their immigration status.
- All community engagement and education should be available in local languages.
- Communicate with faith-based organizations and work with religious leaders to educate communities and build trust.
- Partner with community organizations and support public events (e.g. food distributions, education sessions, etc.).
- Coordinate with the DPH for events and campaigns around health promotion (e.g. mobile testing, flu vaccination).
- Public-facing communications for contact tracing programs should include multi-channel media campaigns in order to reach the highest number of people (i.e. TV, radio, Facebook/Instagram, Google Ads, and town halls).
- Programs should develop partnerships at the community level (i.e. mayors/local councils, health centers, community centers, faith groups, immigrant groups, school superintendents, food pantries, etc.) in order to build trust and combat disinformation.
- Anticipate transmission events and conduct proactive outreach to high risk locations to build trust, reinforce communication, and encourage safe practices (ex. Places of Worship ahead of religious holidays, bars ahead of St. Patrick’s Day/New Years, etc.).
- All media should be developed in local languages and delivered at a hyper-local level (i.e. grocery stores, churches, etc.).
- Consider working with communications companies (cell providers) for increased visibility on CallerID/getting through mobile spam filters.
Metrics should guide every contact tracing program in improving quality and ensuring program effectiveness
- Collecting comprehensive data and ensuring quality reporting and dashboards are essential to monitor delivery across 4 key dimensions of an effective program: Scale, Speed, Retention, and Equity.
- Demographic metrics provide a profile of the contract tracing program – all key performance indicators (KPIs) should be disaggregated by key demographic variables (i.e. gender, race, ethnicity, and language) and analyzed for differences.
- All metrics should have defined targets and progress tracked against these targets; leadership should actively manage progress.
Effective contact tracing programs focus on 4 critical dimensions: equity, scale, speed, and retention.
- Equity: Are we responding to all unique needs with a social justice lens, and prioritizing the most vulnerable groups? Are CRC referrals at the optimized level?
- Scale: Has the response built up the infrastructure to meet demand (e.g., staffing capacity, social support resources)?
- Speed: Is the response happening quickly enough to drive the rate of infection below 1: < 3 days for the full cascade?
- Retention: Where is loss-to-follow-up occurring at each stage in the cascade (i.e. testing to case investigation to contact tracing to follow-up)?
Tool: Partners In Health’s COVID-19 Data Evaluation: Metrics and KPIs, Section 3
- COVID-19 response metrics: # of cases reached, # of cases identified and supported to isolate, # of contacts identified and supported to quarantine, # of educational materials provided
- Social support metrics: % of individuals identified with resource need, referred, and received resource
- Clinical support metrics: % of individuals identified with pre-existing conditions in need of healthcare, referred, and connected to clinical care
- Timing metrics: show how long the entire cascade takes (from time of test to isolation/quarantine) with the goal of <3 days to drive R0 < 1
Tool: Sample Priority Metrics from PIH’s program in Immokalee, Florida
Tool: KPI guidance from PIH - these example key performance indicators (KPIs) provide an example of what contact tracing programs should be measuring and monitoring
Tool: Partners In Health’s COVID-19 Data Evaluation: Metrics and KPIs, Sections 2 and 4
- Case investigation metrics track case status and help identify problems in retention and scale
- Care resource coordination metrics map vulnerability and equity among contacts, particularly demonstrating those who need support to quarantine
Technology can be deployed at multiple times during the contact tracing process. However, technology requires humans to make it work. Contact tracing is not just an epidemiological exercise, it is an exercise in care that cannot be effective through technology alone.
Key digital and technology solutions for contact tracing include
- Local epi surveillance systems: These are the systems of records for all communicable diseases. Positive lab tests are received here. COVID cases can then be transferred to the case & contact management platform. Local or state epi systems may not be able to support the scale of COVID-19 contact tracing.
- Case and contact management platforms (CRMs): CRMs should be able to execute case investigation and contact tracing workflows at scale while collecting and storing data from calls. Data integrity and synchronization between the local epi system and CRM is of utmost importance, as duplicate cases and contacts should be minimized where possible, cases and contacts must be linked to capture the chain of transmission, and case data must be synced rapidly from the epi system to the CRM to ensure swift follow up.
- Proximity tracking tools: Digital tracking systems, often on mobile devices, are used to determine contact between an infected patient and a user. These programs often use Bluetooth or GPS. In the US, adoption of proximity tracking tools has been slow due to privacy concerns. Notably, these automated tools cannot provide care resource coordination and though they can supplement manual contact tracing, they should not replace it.
- Medical monitoring tools: These tools enable remote symptoms monitoring and referral to care and testing. Public health departments can enroll at-risk individuals in the app and monitor symptoms based on patient reports. Thus far, there has been limited data on adoption rates and effectiveness. These tools also lack functionality for referral to social support services and must be integrated into the CRM platform to connect patients to care.
Ensuring the privacy of a case and contact data is of the utmost importance. Contact tracing programs will not work if people don’t trust contact tracers to guard their information correctly and safely. Protected health information should only be used in reference to COVID-19 public health and individual care needs.
- Will the local disease surveillance database be used for the system of record for case data (i.e. MAVEN in MA, NEDSS elsewhere) or will a new system be deployed?
- What case and contact management platform (CRM) will be used to centralize case investigation and contact tracing workflow (i.e. SalesForce, CommCare)?
- What will the intersection be between the CRM and the epidemiological surveillance system? How will the CRM or epi system be updated to reflect the unique COVID-19 needs and considerations?
- Will Bluetooth/GPS proximity tracking or symptom monitoring tools be used widely? If so, how will the contact tracing program interact with those tools?
Contact tracing systems have the opportunity to effect long-term system change.
- Build community health programs that can also contribute to long-term healthcare system strengthening efforts
- Contact tracing programs can build upon existing community health worker programs or become the foundation of a new one
- Train contact tracers and community health workers to refer and accompany people to clinical care to improve access to healthcare even outside of the COVID-19 pandemic
- Combine COVID-19 response strategies with other health promotion activities to increase trust in the health care system
- Flu vaccination, basic primary care services, mobile COVID-19 testing, and COVID-19 vaccination