Increase in COVID-19 Cases and Novel Variant Emergence Could Result From “Vaccine Nationalism”

The allocation of the COVID-19 vaccine between countries has so far tended towards vaccine nationalism, with countries building vaccines to prioritize access for their citizens over the fair sharing of vaccines. However, the magnitude of vaccine nationalism could have a strong impact on the global trajectories of COVID-19 cases and increase the potential emergence of new variants.

The allocation of the COVID-19 vaccine between countries has so far tended towards vaccine nationalism, with countries building vaccines to prioritize access for their citizens over the fair sharing of vaccines. However, the magnitude of vaccine nationalism could have a strong impact on global trajectories in the number of COVID-19 cases and increase the potential emergence of new variants, according to a study from Princeton University and McGill University published Aug. 17, 2021 in the journal Science. published.

“Certain countries such as Peru and South Africa that have had severe COVID-19 outbreaks have received few vaccines, while many doses have gone to countries experiencing relatively milder pandemic impacts, either in terms of mortality or economic disruption,” said Co. —first author Caroline Wagner, an assistant professor of bioengineering at McGill University who previously worked as a postdoctoral research associate at Princeton’s High Meadows Environmental Institute (HMEI).

“As expected, we have seen a large drop in cases in many regions with high vaccine access, but infections are reappearing in areas of low availability,” said co-first author Chadi Saad-Roy, a graduate student of ecology and Princeton’s evolutionary biology. and the Lewis-Sigler Institute for Integrative Genomics.

“Our goal was to explore, using mathematical models, the effects of different vaccine-sharing schemes on the global persistence of COVID-19 infections — as well as the potential for the evolution of new variants,” said Saad-Roy.

The researchers predicted the incidence of COVID-19 cases under a range of vaccine dosing regimens, vaccination rates and assumptions regarding immune responses. They did this in two model regions: one with high access to vaccines – a high access region (HAR) – and a low access region (LAR). The models also made it possible to link the regions through case import or the evolution of a new variant in one of the regions.

“In this way, we were able to assess the dependence of our epidemiological projections on various immunological parameters, regional characteristics such as population size and local transmission rate, and our assumptions regarding vaccine allocation,” Wagner said.

Overall, the study found that an increase in vaccine sharing resulted in a lower number of cases in LARs. “Since it appears that vaccines are very effective in reducing the clinical severity of infections, the public health implications of these reductions are very significant,” said study co-author Michael Mina, an assistant professor at Harvard TH Chan School. of Public Health.

Senior author C. Jessica E. Metcalf, a Princeton associate professor of ecology and evolutionary biology and public affairs and associate faculty in HMEI, added, “High numbers of cases in unvaccinated populations are likely to be associated with higher rates of hospitalization and greater clinical burden.” compared for highly vaccinated populations.”

The authors also used a framework developed in their previous work to try to quantify the potential for viral evolution under different vaccine-sharing schedules. In their model, repeated infections in individuals with partial immunity — either from a previous infection or a vaccine — can result in the evolution of new variants.

“Overall, the models predict that sustained increased case numbers in LARs with limited vaccine availability will result in a high potential for viral evolution,” said senior author Bryan Grenfell, Princeton’s Kathryn Briger and Sarah Fenton Professor of Ecology and Evolutionary Biology and Public Affairs. and an associate faculty member in HMEI.

“As with our previous work, the current study strongly underlines the importance of rapid, equitable worldwide vaccine distribution,” Grenfell said. “In a plausible scenario in which secondary infections in previously infected individuals strongly contribute to viral evolution, unequal vaccine allocation appears particularly problematic.”

As the pandemic continues, viral evolution may play an increasing role in sustaining transmission, said senior author Simon Levin, Princeton’s James S. McDonnell Distinguished University Professor in Ecology and Evolutionary Biology and an associate faculty member in HMEI. “In particular, antigen novel variants have the potential to threaten immunization efforts worldwide through several mechanisms,” he said, “including higher transmissibility, reduced vaccine efficacy or immune escape.”

Saad-Roy added: “In this way, global vaccine coverage will reduce the clinical burden of new variants, while also reducing the likelihood of these variants appearing.”

There are additional considerations for vaccine equivalence beyond epidemiological and evolutionary, said study co-author Ezekiel Emanuel, the Diane vs. Levy and Robert M. Levy University Professor and co-director of the Healthcare Transformation Institute at the University of Pennsylvania.

“Ethics also argue against countries building vaccines or allocating doses for boosters,” Emanuel said. “This study strongly supports that ethical view that stockpiling will undermine global health.”

Co-author Jeremy Farrar, director of the Wellcome Trust, UK, said the timing of when vaccines are shared is also likely to be critical: “Particularly parallel sharing is what has the greatest impact, not in order.”

Reference: “Vaccine Nationalism and the Dynamics and Control of SARS-CoV-2” by Caroline E. Wagner, Chadi M. Saad-Roy, Sinead E. Morris, Rachel E. Baker, Michael J. Mina, Jeremy Farrar, Edward C Holmes , Oliver G. Pybus, Andrea L. Graham, Ezekiel J. Emanuel, Simon A. Levin, C. Jessica E. Metcalf, and Bryan T. Grenfell, Aug. 17, 2021, Science.
DOI: 10.1126/science.abj7364

Other co-authors of the study include Sinead Morris, a postdoctoral researcher at Columbia University who completed her Ph.D. in Ecology and Evolutionary Biology from Princeton; Rachel Baker, an associate researcher at HMEI; Andrea Graham, professor of ecology and evolutionary biology at the faculty of Princeton and HMEI; Edward Holmes, an Australian ARC laureate and professor at the University of Sydney; and Oliver Pybus, professor of evolution and infectious diseases at the University of Oxford.

The article, “Vaccine Nationalism and the Dynamics and Control of SARS-CoV-2,” was published online Aug. 17 by Science. The work was supported by funds from the Natural Sciences and Engineering Research Council of Canada, the Cooperative Institute for Modeling the Earth System at Princeton University, the James S. McDonnell Foundation, the C3.ai Digital Transformation Institute and Microsoft Corporation, Google, the National Science Foundation, the US Centers for Disease Control and Prevention, and Flu Lab.