COVID-19 cases and hospitalizations averted by case investigation and contact tracing in the United States

  1. Gabriel Rainisch
  2. Seonghye Jeon
  3. Danielle Pappas
  4. Kimberly D. Spencer
  5. Leah S. Fischer
  6. Bishwa B. Adhikari
  7. Melanie M. Taylor
  8. Bradford Greening
  9. Patrick K. Moonan
  10. John E. Oeltmann
  11. Emily B. Kahn
  12. Michael L. Washington
  13. Martin I. Meltzer

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Abstract

Importance

Evidence of the impact of COVID-19 Case Investigation and Contact Tracing (CICT) programs is lacking. Policymakers need this evidence to assess its value.

Objective

Estimate COVID-19 cases and hospitalizations averted nationwide by US states’ CICT programs.

Design

We combined data from US CICT programs ( e . g ., proportion of cases interviewed, contacts notified or monitored, and days to case and contact notification) with incidence data to model CICT impacts over 60 days period (November 25, 2020 to January 23, 2021) during the height of the pandemic. We estimated a range of impacts by varying assumed compliance with isolation and quarantine recommendations.

Setting

US States and Territories

Participants

Fifty-nine state and territorial health departments that received federal funding supporting COVID-19 pandemic response activities were eligible for inclusion. Of these, 22 states and 1 territory reported all measures necessary for the analysis. These 23 jurisdictions covered 42.5% of the US population (140 million persons), spanned all 4 census regions, and reported data that reflected all 59 federally funded CICT programs.

Intervention

Public health case investigation and contact tracing

Main Outcomes and Measures

Cases and hospitalizations averted; percent of cases averted among cases not prevented by vaccination and other non-pharmaceutical interventions (other NPIs).

Results

We estimated 1.11 million cases and 27,231 hospitalizations were averted by CICT programs under a scenario where 80% of interviewed cases and monitored contacts, and 30% of notified contacts fully complied with isolation and quarantine guidance, eliminating their contributions to future transmission. As many as 1.36 million cases and 33,527 hospitalizations could have been prevented if all interviewed cases and monitored contacts had entered into and fully complied with isolation and quarantine guidelines upon being interviewed or notified. Across all scenarios and jurisdictions, CICT averted a median of 21.2% (range: 1.3% – 65.8%) of the cases not prevented by vaccination and other NPIs.

Conclusions and Relevance

CICT programs likely had a substantial role in curtailing the pandemic in most jurisdictions during the winter 2020-2021 peak. Differences in impact across jurisdictions indicate an opportunity to further improve CICT effectiveness. These estimates demonstrate the potential benefits from sustaining and improving these programs.

KEY POINTS

Question

What were the health impacts of COVID-19 case investigation and contact tracing programs (CICT) in the US?

Findings

By combining CICT program data from 22 states and 1 territory with mathematical modeling, we estimate CICT averted between 1.11 to 1.36 million cases and 27,231 to 33,527 hospitalizations over 60 days during the height of the pandemic (winter 2020-21). The upper estimate assumes all interviewed cases and monitored contacts complied with isolation and quarantine guidelines, while the lower estimate assumes fractions of interviewed cases and monitored or notified contacts did so.

Meaning

CICT programs likely played a critical role in curtailing the pandemic.

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  3. ScreenIT

    SciScore for 10.1101/2021.11.19.21266580: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Our study also has limitations. Jurisdictions’ self-reported CICT performance measures were not intended for this analysis. Although we employed the previously described data quality checks (eFigure 3 in Supplement 1), the reported measures that we used were likely influenced by differences in jurisdictions’ surveillance systems, CICT platforms and protocols (e.g., how they enrolled and monitored contacts). The extent to which these differences affected our results is unclear. We also only assess the impact over two months (60 days) of the pandemic and in 23 US jurisdictions. Results may differ for other periods (e.g., during the surge of the Delta variant and wider use of vaccine) and jurisdictions. Because cases were spiking across the entire US during the period that we analyzed and the vaccine had not yet been widely administered, it is likely that our estimates provide an upper limit of cases averted by CICT during the pandemic as of this writing (August 31, 2021). Finally, because we used statewide data, our results dilute potentially meaningful differences in CICT performance within jurisdictions (e.g., rural versus urban counties). Our analysis combined primary implementation data with mathematical modeling to estimate the health impact of COVID-19 case investigation and contact tracing across nearly half of US state and territory CICT programs. The volume of estimated cases and hospitalizations averted underscores the critical role CICT programs play in curtailing th...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a protocol registration statement.

    Results from scite Reference Check: We found no unreliable references.

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  4. Version published to 10.1101/2021.11.19.21266580v1 on medRxiv