When Can We Lift Non-Pharmaceutical Interventions with the Availability of COVID-19 Vaccine in the United States?
Abstract
Research Objective
Coronavirus disease 2019 (COVID-19), a global pandemic, has disproportionately inflicted deaths and affected the US economy. With the recent emergency use authorization of COVID-19 vaccines, ongoing non-pharmaceutical interventions (NPIs) could be lifted in the future. Our objective was to quantify the impact of the timing of the lifting of NPIs on COVID-19 infections and deaths.
Study Design
We developed a dynamic transmission model with Susceptible-Exposed-Infectious-Recovered (SEIR) compartments to simulate the evolution of COVID-19 over time in the United States from March 2020 to December 2021. We accounted for heterogeneity by including seven age groups and four contact mixing domains (school, work, household, and other locations) relevant to SARS-CoV-2 transmission. We extracted model parameters from published studies, available databases, and via calibration. We also calibrated the effect of NPIs (e.g., restriction on businesses, mask mandates, limited indoor gathering) on contact rates within each mixing domain. The model was calibrated to reproduce COVID-19 deaths, reported infections and hospitalizations from March–December. We introduced the COVID-19 vaccine from January 2021, assuming an uptake rate of 15 million individuals per month and a prioritization schedule as defined by the Centers for Disease Control and Prevention. We assumed a vaccine efficacy of 70–90% (base case: 90%) for protection against developing COVID-19 symptoms, and we assumed 25% (relative to vaccine efficacy) of the protection against COVID-19 infection. We projected the total numbers of COVID-19 infections (diagnosed and undiagnosed), hospitalizations, and deaths in 2021 if NPIs are lifted in August, September, October, November, and not lifted in 2021.
Population Studied
US Population.
Principal Findings
Maintaining all NPIs in the US throughout 2021 is predicted to result in 36,300 deaths (22,700 deaths in age 70+), 11.19 million total COVID-19 infections (6.20 million diagnosed; and 2.11 million moderate/severe), 84,000 intensive care unit (ICU) admissions. TABLE shows the difference in outcomes if NPIs are lifted (compared with maintaining NPIs throughout 2021) in August, September, October, and November. All scenarios of the lifting of NPIs would result in additional deaths, infections, and hospitalizations. Sensitivity analysis showed that with the vaccine efficacy of 70%, the difference in outcomes would increase further.
| Outcome | Jan-Dec 2021 | Excess Outcomes with NPIs Lifting in: | |||
|---|---|---|---|---|---|
| Maintain NPIs in 2021 | Aug-2021 | Sep-2021 | Oct-2021 | Nov-2021 | |
| Deaths: total | 36,340 | +262,956 | +125,536 | +28,708 | +3360 |
| age 0–19 | 71 | +1299 | +774 | +221 | +30 |
| age 20–69 | 13,572 | +89,067 | +44,546 | +10,711 | +1371 |
| age 70+ | 22,697 | +172,591 | +80,215 | +17,776 | +1959 |
| Infections: total | 11.19 M | +165.88 M | +110.10 M | +35.14 M | +5.29 M |
| undiagnosed | 4.99 M | +84.63 M | +58.08 M | +19.31 M | +2.96 M |
| diagnosed | 6.20 M | +81.24 M | +51.98 M | +15.82 M | +2.33 M |
| Infections: moderate/severe | 2.11 M | +21.31 M | +13.48 M | +4.09 M | +0.60 M |
| Infections: asymptomatic/mild | 9.07 M | +144.56 M | +96.58 M | +31,051,361 | +4,691,031 |
| Hospitalizations | 224,247 | +2,179,487 | +1,394,693 | +455,218 | +69,833 |
| ICU admissions | 83,967 | +738,179 | +427,519 | +121,676 | +16,888 |
Conclusions
Even though COVID-19 vaccines are being deployed through emergency use approvals in the US, the time at which NPIs are lifted will still have a substantial influence on COVID-19 mortality during 2021.
Implications for Policy or Practice
Social distancing and restrictions on businesses are needed, potentially throughout 2021, to mitigate COVID-19 hospitalizations and deaths in the United States before immunity through vaccination programs can become effective.
Primary Funding Source
Janssen.
