Under what circumstances could vaccination offset the harm from a more transmissible variant of SARS-COV-2 in NYC? Trade-offs regarding prioritization and speed of vaccination
Authors: Kim Hae-Young , Bershteyn Anna , McGillen Jessica B. , Braithwaite R. Scott 
Published: February 2021

Introduction

New York City (NYC) was a global epicenter of COVID-19. Vaccines against COVID-19 became available in December 2020 with limited supply, resulting in the need for policies regarding prioritization. The next month, SARS-CoV-2 variants were detected that were more transmissible but still vaccine-susceptible, raising scrutiny of these policies. In particular, prioritization of higher-risk people could prevent more deaths per dose of vaccine administered but could also delay herd immunity if the prioritization introduced bottlenecks that lowered vaccination speed (the number of doses that could be delivered per day). We used mathematical modeling to examine the trade-off between prioritization and the vaccination speed.

Methods

A stochastic, discrete-time susceptible-exposed-infected-recovered (SEIR) model with age- and comorbidity-adjusted COVID-19 outcomes (infections, hospitalizations, and deaths by July 1, 2021) was used to examine the trade-off between vaccination speed and whether or not vaccination was prioritized to individuals age 65+ and “essential workers,” defined as including first responders and healthcare, transit, education, and public safety workers. The model was calibrated to COVID-19 hospital admissions, hospital census, ICU census, and deaths in NYC. Vaccination speed was assumed to be 10,000 doses per day starting December 15th, 2020 targeting healthcare workers and nursing home populations, and to subsequently expand at alternative starting times and speeds. We compared COVID-outcomes across alternative expansion starting times (January 15th, January 21st, or February 1st) and speeds (20,000, 30,000, 50,000, 100,000, 150,000, or 200,000 doses per day for the first dose), as well as alternative prioritization options (“yes” versus “no” prioritization of essential workers and people age 65+). Model projections were produced with and without considering the emergence of a SARS-COV-2 variant with 56% greater transmissibility over January and February, 2021.

Results

In the absence of a COVID-19 vaccine, the emergence of the more transmissible variant would triple the peak in infections, hospitalizations, and deaths and more than double cumulative infections, hospitalizations, and deaths. To offset the harm from the more transmissible variant would require reaching a vaccination speed of at least 100,000 doses per day by January 15th or 150,000 per day by January 21st. Prioritizing people ages 65+ and essential workers increased the number of lives saved per vaccine dose delivered: with the emergence of a more transmissible variant, 8,000 deaths could be averted by delivering 115,000 doses per day without prioritization or 71,000 doses per day with prioritization. If prioritization were to cause a bottleneck in vaccination speed, more lives would be saved with prioritization only if the bottleneck reduced vaccination speed by less than one-third of the maximum vaccine delivery capacity. These trade-offs between vaccination speed and prioritization were robust over a wide range of delivery capacity.

Conclusions

The emergence of a more transmissible variant of SARS-CoV-2 has the potential to triple the 2021 epidemic peak and more than double the 2021 COVID-19 burden in NYC. Vaccination could only offset the harm of the more transmissible variant if high speed were achieved in mid-to late January. Prioritization of COVID-19 vaccines to higher-risk populations saves more lives only if it does not create an excessive vaccine delivery bottleneck.