1. Epidemiology and Global Health

Projected resurgence of COVID-19 in the United States in July—December 2021 resulting from the increased transmissibility of the Delta variant and faltering vaccination

  1. Shaun Truelove  Is a corresponding author
  2. Claire P Smith
  3. Michelle Qin
  4. Luke C Mullany
  5. Rebecca K Borchering
  6. Justin Lessler
  7. Katriona Shea
  8. Emily Howerton
  9. Lucie Contamin
  10. John Levander
  11. Jessica Kerr
  12. Harry Hochheiser
  13. Matt Kinsey
  14. Kate Tallaksen
  15. Shelby Wilson
  16. Lauren Shin
  17. Kaitlin Rainwater-Lovett
  18. Joseph C Lemairtre
  19. Juan Dent
  20. Joshua Kaminsky
  21. Elizabeth C Lee
  22. Javier Perez-Saez
  23. Alison Hill
  24. Dean Karlen
  25. Matteo Chinazzi
  26. Jessica T Davis
  27. Kunpeng Mu
  28. Xinyue Xiong
  29. Ana Pastore y Piontti
  30. Alessandro Vespignani
  31. Ajitesh Srivastava
  32. Przemyslaw Porebski
  33. Srinivasan Venkatramanan
  34. Aniruddha Adiga
  35. Bryan Lewis
  36. Brian Klahn
  37. Joseph Outten
  38. Mark Orr
  39. Galen Harrison
  40. Benjamin Hurt
  41. Jiangzhuo Chen
  42. Anil Vullikanti
  43. Madhav Marathe
  44. Stefan Hoops
  45. Parantapa Bhattacharya
  46. Dustin Machi
  47. Shi Chen
  48. Rajib Paul
  49. Daniel Janies
  50. Jean-Claude Thill
  51. Marta Galanti
  52. Teresa K Yamana
  53. Sen Pei
  54. Jeffrey L Shaman
  55. Jessica M Healy
  56. Rachel B Slayton
  57. Matthew Biggerstaff
  58. Michael A Johansson
  59. Michael C Runge
  60. Cecile Viboud
  1. Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, United States
  2. Harvard University, United States
  3. Johns Hopkins University Applied Physics Laboratory, United States
  4. Pennsylvania State University, United States
  5. University of North Carolina at Chapel Hill, United States
  6. University of Pittsburgh, United States
  7. École polytechnique fédérale de Lausanne, Switzerland
  8. University of Victoria, Canada
  9. Northeastern University, United States
  10. University of Southern California, United States
  11. University of Virginia, United States
  12. University of North Carolina at Charlotte, United States
  13. Columbia University, United States
  14. CDC COVID-19 Response Team, United States
  15. United States Geological Survey, United States
  16. Fogarty International Center, National Institutes of Health, United States
https://doi.org/10.7554/eLife.73584
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Cite this article
  1. Shaun Truelove
  2. Claire P Smith
  3. Michelle Qin
  4. Luke C Mullany
  5. Rebecca K Borchering
  6. Justin Lessler
  7. Katriona Shea
  8. Emily Howerton
  9. Lucie Contamin
  10. John Levander
  11. Jessica Kerr
  12. Harry Hochheiser
  13. Matt Kinsey
  14. Kate Tallaksen
  15. Shelby Wilson
  16. Lauren Shin
  17. Kaitlin Rainwater-Lovett
  18. Joseph C Lemairtre
  19. Juan Dent
  20. Joshua Kaminsky
  21. Elizabeth C Lee
  22. Javier Perez-Saez
  23. Alison Hill
  24. Dean Karlen
  25. Matteo Chinazzi
  26. Jessica T Davis
  27. Kunpeng Mu
  28. Xinyue Xiong
  29. Ana Pastore y Piontti
  30. Alessandro Vespignani
  31. Ajitesh Srivastava
  32. Przemyslaw Porebski
  33. Srinivasan Venkatramanan
  34. Aniruddha Adiga
  35. Bryan Lewis
  36. Brian Klahn
  37. Joseph Outten
  38. Mark Orr
  39. Galen Harrison
  40. Benjamin Hurt
  41. Jiangzhuo Chen
  42. Anil Vullikanti
  43. Madhav Marathe
  44. Stefan Hoops
  45. Parantapa Bhattacharya
  46. Dustin Machi
  47. Shi Chen
  48. Rajib Paul
  49. Daniel Janies
  50. Jean-Claude Thill
  51. Marta Galanti
  52. Teresa K Yamana
  53. Sen Pei
  54. Jeffrey L Shaman
  55. Jessica M Healy
  56. Rachel B Slayton
  57. Matthew Biggerstaff
  58. Michael A Johansson
  59. Michael C Runge
  60. Cecile Viboud
(2022)
Projected resurgence of COVID-19 in the United States in July—December 2021 resulting from the increased transmissibility of the Delta variant and faltering vaccination
eLife 11:e73584.
https://doi.org/10.7554/eLife.73584
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  3. Download .RIS
3 figures, 1 table and 2 additional files

Figures

Figure 1 with 3 supplements
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Historical data and weekly ensemble projections of reported numbers of COVID-19 cases.

(A) Hospitalizations (B) and deaths (C) under four scenarios representing different levels of vaccination and Delta variant transmissibility increase — United States, October, 2020–December, 2021.Projections are ensemble estimates of 9 models projecting four 6-month scenarios with 95% prediction intervals (the grey shading encompasses the prediction intervals from all four scenarios). Projections used empirical data from up to July 3, 2021, to calibrate models (black filled dots). The vertical lines indicate the beginning of each projection, with only data available prior to that point used to fit the projections. Observations available after the projection start are displayed as open dots.

Figure 1—figure supplement 1
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Historical data and weekly individual projections of reported numbers of COVID-19 cases under four scenarios representing different levels of vaccination and Delta variant transmissibility increase — United States, October 2020–December 2021.

Solid color lines and shaded areas represent median projections and 95% prediction intervals of reported cases for the entire US from each of the 9 models for each of the four scenarios. Projections used empirical data from up to July 3, 2021, to calibrate models (black filled dots). The vertical lines indicate the beginning of each projection, with only data available prior to that point used to fit the projections. Observations available after the projection start are displayed as open dots.

Figure 1—figure supplement 2
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Historical data and weekly individual projections of reported numbers of COVID-19 hospitalizations under four scenarios representing different levels of vaccination and Delta variant transmissibility increase — United States, October 2020–December 2021.

Solid color lines and shaded areas represent median projections and 95% prediction intervals of reported hospitalizations for the entire US from each of the 9 models for each of the four scenarios. Projections used empirical data from up to July 3, 2021, to calibrate models (black filled dots). The vertical lines indicate the beginning of each projection, with only data available prior to that point used to fit the projections. Observations available after the projection start are displayed as open dots.

Figure 1—figure supplement 3
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Historical data and weekly individual projections of reported numbers of COVID-19 deaths under four scenarios representing different levels of vaccination and Delta variant transmissibility increase — United States, October 2020–December 2021.

Solid color lines and shaded areas represent median projections and 95% prediction intervals of reported deaths for the entire US from each of the 9 models for each of the four scenarios. Projections used empirical data from up to July 3, 2021, to calibrate models (black filled dots). The vertical lines indicate the beginning of each projection, with only data available prior to that point used to fit the projections. Observations available after the projection start are displayed as open dots.

Figure 2
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Projected cumulative cases and mortality in the most pessimistic scenario (low vaccination, high variant transmissibility) and current vaccination coverage by state — United States, July 4, 2021–January 1, 2022.

(A) Correlation between cumulative projected cases per 10,000 population during the 6-month period and proportion of the eligible population vaccinated with at least one COVID-19 vaccine dose by July 3, 2021, by state. Circle sizes represent population size. Single dose coverage was used as data reporting were most reliable for the first dose at the time of this analysis; yet second dose coverage is highly correlated with first dose coverage (Pearson rho = 0.92 on July 3, 2021, p<10–15). (B) Cumulative projected cases per 10,000 population during the 6-month period, by state. (C) Correlation between cumulative projected deaths per 10,000 population during the 6-month period and proportion of the eligible population vaccinated with at least one COVID-19 vaccine dose by July 3, 2021, by state. Circle sizes represent population size. (D) Cumulative projected deaths per 10,000 population during the 6-month period, by state.

Figure 3
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Comparison of the median projected and observed state-level total COVID-19 case incidences occurring during July 4–31, 2021, United States.

Comparison is based on ranking of incidence per capita in 50 states + DC (Spearman’s rank correlation = 0.867). The grey solid line represents perfect agreement between ranks (y=x), which overlays a regression line fitted to the data (dashed line) and 95% confidence intervals (grey shaded area).

Tables

Table 1
COVID-19 projection scenarios* — United States, July 4, 2021–January 1, 2022.

Scenarios defined for projection of COVID-19 cases, hospitalizations, and deaths for the sixth round of projections through the COVID-19 Scenario Modeling Hub§.

Low impact variant;(low transmissibility increase)High impact variant;(high transmissibility increase)
High vaccination;
(low hesitancy)		Vaccination:

  • Coverage saturates at 80% nationally among the vaccine-eligible population* by December 31, 2021†

  • VE is 50%/90% for Pfizer/Moderna against currently circulating variants (1st /2nd dose) and 60% for J&J (1 dose)

  • J&J no longer used†*

Variant:

  • 40% increased transmissibility as compared with Alpha for Delta variant. Initial prevalence estimated at state-level by teams.

Vaccination:

  • Coverage saturates at 80% nationally among the vaccine-eligible population* by December 31, 2021†

  • VE is 35%/85% for Pfizer/Moderna against currently circulating variants (1st /2nd dose) and 60% for J&J (1 dose)

  • J&J no longer used†*

Variant:

  • 60% increased transmissibility as compared with Alpha for Delta variant. Initial prevalence estimated at state-level by teams.

Low vaccination;
(high hesitancy)		Vaccination:

  • Coverage saturates at 70% nationally among the vaccine-eligible population* by December 31, 2021†

  • VE is 50%/90% for Pfizer/Moderna against currently circulating variants (1st /2nd dose) and 60% for J&J (1 dose)

  • J&J no longer used†*

Variant:

  • 40% increased transmissibility as compared with Alpha for Delta variant. Initial prevalence estimated at state-level by teams.

Vaccination:

  • Coverage saturates at 70% nationally among the vaccine-eligible population* by December 31, 2021†

  • VE is 35%/85% for Pfizer/Moderna against currently circulating variants (1st /2nd dose) and 60% for J&J (1 dose)

  • J&J no longer used ‡

Variant:

  • 60% increased transmissibility as compared with Alpha for Delta variant. Initial prevalence estimated at state-level by teams.

  1. *

    The Vaccine-eligible population is presumed to be individuals aged 12 years and older through the end of the projection period.

  2. †

    Vaccine hesitancy expected to cause vaccination coverage to slow and eventually saturate at some level below 100%. The saturation levels provided in these scenarios are National reference points to guide defining hesitancy, though the speed of that saturation and heterogeneity between states (or other geospatial scales) and/or age groups are at the discretion of the modeling team (COVID-19 Scenario Modeling Hub, 2020). The high vaccination 80% saturation is defined using the current estimates from the Delphi group (updated from Round 6) (Carnegie Mellon University Delphi Group, 2021). The low saturation estimate of 70% is the lowest county-level estimate from the US Census Bureau’s Pulse Survey from May 26-June 7, 2021 data (Estimates of Vaccine Hesitancy for COVID-19, 2021).

  3. ‡

    To simplify the models and future projections of vaccine administration, it was assumed continued administration of the Johnson & Johnson (J&J) vaccine would not occur on or after the projection date (after July 4, 2021) due to the limited amount administered previously in the US (as of August 4, 2021 approximately 4 million doses delivered since April 13, 2021 compared to 153 million for Pfizer and Moderna) (Centers for Disease Control and Prevention, 2021b).

  4. §

    COVID-19 Scenario Modeling Hub: https://covid19scenariomodelinghub.org/.

Additional files

Supplementary file 1

Summary of model assumptions for the seventh round of long-term scenario projections from the US COVID-19 Scenario Modeling Hub.

This table details a summary of core model assumptions for the nine included models (arranged alphabetically).

https://cdn.elifesciences.org/articles/73584/elife-73584-supp1-v2.xlsx
MDAR checklist
https://cdn.elifesciences.org/articles/73584/elife-73584-mdarchecklist1-v2.docx

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  1. Shaun Truelove
  2. Claire P Smith
  3. Michelle Qin
  4. Luke C Mullany
  5. Rebecca K Borchering
  6. Justin Lessler
  7. Katriona Shea
  8. Emily Howerton
  9. Lucie Contamin
  10. John Levander
  11. Jessica Kerr
  12. Harry Hochheiser
  13. Matt Kinsey
  14. Kate Tallaksen
  15. Shelby Wilson
  16. Lauren Shin
  17. Kaitlin Rainwater-Lovett
  18. Joseph C Lemairtre
  19. Juan Dent
  20. Joshua Kaminsky
  21. Elizabeth C Lee
  22. Javier Perez-Saez
  23. Alison Hill
  24. Dean Karlen
  25. Matteo Chinazzi
  26. Jessica T Davis
  27. Kunpeng Mu
  28. Xinyue Xiong
  29. Ana Pastore y Piontti
  30. Alessandro Vespignani
  31. Ajitesh Srivastava
  32. Przemyslaw Porebski
  33. Srinivasan Venkatramanan
  34. Aniruddha Adiga
  35. Bryan Lewis
  36. Brian Klahn
  37. Joseph Outten
  38. Mark Orr
  39. Galen Harrison
  40. Benjamin Hurt
  41. Jiangzhuo Chen
  42. Anil Vullikanti
  43. Madhav Marathe
  44. Stefan Hoops
  45. Parantapa Bhattacharya
  46. Dustin Machi
  47. Shi Chen
  48. Rajib Paul
  49. Daniel Janies
  50. Jean-Claude Thill
  51. Marta Galanti
  52. Teresa K Yamana
  53. Sen Pei
  54. Jeffrey L Shaman
  55. Jessica M Healy
  56. Rachel B Slayton
  57. Matthew Biggerstaff
  58. Michael A Johansson
  59. Michael C Runge
  60. Cecile Viboud
(2022)
Projected resurgence of COVID-19 in the United States in July—December 2021 resulting from the increased transmissibility of the Delta variant and faltering vaccination
eLife 11:e73584.
https://doi.org/10.7554/eLife.73584