key: cord-0865794-k51dir3y
authors: Walker, Joseph; Paul, Prabasaj; Dooling, Kathleen; Oliver, Sara; Prasad, Pragati; Steele, Molly; Gastañaduy, Paul A.; Johansson, Michael A.; Biggerstaff, Matthew; Slayton, Rachel B.
title: Modeling Strategies for the Allocation of SARS-CoV-2 Vaccines in the United States
date: 2022-02-07
journal: Vaccine
DOI: 10.1016/j.vaccine.2022.02.015
sha: 459858bc6791900d5bdc2730015f66bf4b63d769
doc_id: 865794
cord_uid: k51dir3y

The Advisory Committee on Immunization Practices (ACIP) recommended phased allocation of SARS-CoV-2 vaccines in December 2020. To support the development of this guidance, we used a mathematical model of SARS-CoV-2 transmission to evaluate the relative impact of three vaccine allocation strategies on infections, hospitalizations, and deaths. All three strategies initially prioritized healthcare personnel (HCP) for vaccination. Strategies of subsequently prioritizing adults aged ≥65 years, or a combination of essential workers and adults aged ≥75 years, prevented the most deaths. Meanwhile, prioritizing adults with high-risk medical conditions immediately after HCP prevented the most infections. All three strategies prevented a similar fraction of hospitalizations. While no model is capable of fully capturing the complex social dynamics which shape epidemics, exercises such as this one can be a useful way for policy makers to formalize their assumptions and explore the key features of a problem before making decisions.

Abstract 27 The Advisory Committee on Immunization Practices (ACIP) recommended phased allocation of 28 SARS-CoV-2 vaccines in December 2020. To support the development of this guidance, we used 29 a mathematical model of SARS-CoV-2 transmission to evaluate the relative impact of three 30 vaccine allocation strategies on infections, hospitalizations, and deaths. All three strategies 31 initially prioritized healthcare personnel (HCP) for vaccination. Strategies of subsequently 32 prioritizing adults aged ≥65 years, or a combination of essential workers and adults aged ≥75 33 years, prevented the most deaths. Meanwhile, prioritizing adults with high-risk medical 34 conditions immediately after HCP prevented the most infections. All three strategies prevented 35 a similar fraction of hospitalizations. While no model is capable of fully capturing the complex 36 social dynamics which shape epidemics, exercises such as this one can be a useful way for 37 policy makers to formalize their assumptions and explore the key features of a problem before 38 making decisions.

Introduction 43 With the expectation that early demand for SARS-CoV-2 vaccines would exceed supply for an 44 extended period following introduction, the COVID-19 Vaccine Work Group of the ACIP began 45 to develop a framework for evaluating phased vaccine allocation strategies in the spring of 46 2020, to provide guidance to federal, state, and local decision makers. Work group members 47 considered evidence on the epidemiology of SARS-CoV-2, data on specific vaccines, vaccine 48 program implementation issues, and ethical principles. [1] 49 To support the development of ACIP guidance, we used a compartmental model of SARS-CoV-2 50 transmission in the United States to compare the relative impact of vaccination on infections, 51 hospitalizations, and deaths across several phased allocation strategies considered by the work 52 group. This modeling approach allowed us to simulate patterns of transmission within and 53 between different population groups over time, the progression of some infections to 54 hospitalization or death, and the effect of vaccination on each of these processes. After setting 55 up the model, we compared strategies in which the initial vaccination phases include 56 healthcare personnel and then either prioritize vaccination for adults with high-risk medical 57 conditions, adults aged 65 years or older, or a combination of essential workers and adults aged 58 75 years or older. [1] 59 60

Model Description 62 We used a deterministic SEPIR (Susceptible, Exposed, Pre-symptomatic infectious, symptomatic 63 Infectious, and Recovered) compartmental model to simulate SARS-CoV-2 transmission in the 64 US (including territories) across 6 age groups (0-4, 5-17, 18-49, 50-64, 65-74, and ≥75 years old). 65 The 65-74 and ≥75 years old age groups were each split into 2 subgroups (those with and 66 without a high-risk medical condition), while the 18-49 and 50-64 age groups were stratified 67 into 4 subgroups each (essential workers and non-essential workers with and without a high-68 risk medical condition), for a total of 14 population strata. For the purpose of this analysis, high-69 risk medical conditions include chronic obstructive pulmonary disease, heart disease, diabetes, 

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