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
- Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, United States
- Harvard University, United States
- Johns Hopkins University Applied Physics Laboratory, United States
- Pennsylvania State University, United States
- University of North Carolina at Chapel Hill, United States
- University of Pittsburgh, United States
- École polytechnique fédérale de Lausanne, Switzerland
- University of Victoria, Canada
- Northeastern University, United States
- University of Southern California, United States
- University of Virginia, United States
- University of North Carolina at Charlotte, United States
- Columbia University, United States
- CDC COVID-19 Response Team, United States
- United States Geological Survey, United States
- Fogarty International Center, National Institutes of Health, United States
Figures
Figure 1 with 3 supplements
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
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
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
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
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
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:
| Vaccination:
|
| Low vaccination; (high hesitancy) | Vaccination:
| Vaccination:
|
-
*
The Vaccine-eligible population is presumed to be individuals aged 12 years and older through the end of the projection period.
-
†
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).
-
‡
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).
-
§
COVID-19 Scenario Modeling Hub: https://covid19scenariomodelinghub.org/.
Additional files
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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
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MDAR checklist
- https://cdn.elifesciences.org/articles/73584/elife-73584-mdarchecklist1-v2.docx
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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
