Vaccine nationalism and the dynamics and control of SARS-CoV-2.

Caroline E Wagner,Edward C Holmes,Simon A Levin,Sinead E Morris,Jeremy Farrar,Rachel E Baker,Michael J Mina,Bryan T Grenfell,Ezekiel J Emanuel,Chadi M Saad-Roy,Oliver G Pybus,Andrea L Graham,C Jessica E Metcalf

doi:10.1126/science.abj7364

Abstract

Vaccines provide powerful tools to mitigate the enormous public health and economic costs that the ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic continues to exert globally, yet vaccine distribution remains unequal among countries. To examine the potential epidemiological and evolutionary impacts of “vaccine nationalism,” we extend previous models to include simple scenarios of stockpiling between two regions. In general, when vaccines are widely available and the immunity they confer is robust, sharing doses minimizes total cases across regions. A number of subtleties arise when the populations and transmission rates in each region differ, depending on evolutionary assumptions and vaccine availability. When the waning of natural immunity contributes most to evolutionary potential, sustained transmission in low-access regions results in an increased potential for antigenic evolution, which may result in the emergence of novel variants that affect epidemiological characteristics globally. Overall, our results stress the importance of rapid, equitable vaccine distribution for global control of the pandemic.

Highlights

Due to strong public and political pressures and fear of waning immunity, some countries with high vaccine availability are currently resorting to ‘vaccine nationalism’: stockpiling vaccines to prioritize rapid access to their citizenry [10]
The World Health Organization recognized that delayed access to vaccines in countries with low vaccine availability may lead to more evolutionary potential [12], which could result in immune escape or other phenotypic changes of interest
In the first “decoupled” framework, we assume that the epidemiological dynamics of both countries are entirely independent, with the exception of their respective vaccination rates; we compute a measure for the global potential for viral evolution of immune escape [6]

Summary

Introduction

Due to strong public and political pressures and fear of waning immunity, some countries with high vaccine availability are currently resorting to ‘vaccine nationalism’: stockpiling vaccines to prioritize rapid access to their citizenry [10]. We have recently shown that the strength and duration of immunity elicited following infection or one or two doses of a vaccine will have a crucial impact on the medium-term epidemiological and potential evolutionary outcomes [5, 6]. We extend these analyses to address potential epidemiological and evolutionary consequences of policies of vaccine nationalism or equitable access for a range of assumptions regarding the robustness of host immune responses. The full mathematical details for both frameworks are described in the supplementary materials

Methods

Findings

Conclusion