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Princeton researchers expose consequences of vaccine nationalism

A Princeton University and McGill University study published Aug. 17 in Science journal revealed that vaccine nationalism may lead to increases in the transmission of COVID-19.

The authors define vaccine nationalism as the “stockpiling [of] vaccines to prioritize rapid access to their citizenry.”

The researchers examined the transnational implications of vaccine nationalism by testing various assumptions in a high access region (HAR) and a low access region (LAR). They found, through more equitable vaccine sharing between HAR and LAR countries, that infections and the potential for antigenic evolution, or the emergence of new strains of the virus, would decrease.

“Vaccine nationalism, dosing regimes, and host immune responses have important interactive effects, and these will substantially shape epidemiological dynamics and evolutionary potential in the medium term,” the study said.

The authors reached this conclusion through the creation of two models: a decoupled and coupled framework. The decoupled framework assumes that the epidemiological dynamics of two countries in a specific scenario are independent of each other. In the coupled framework, the authors assume some immigration between countries and the potential for mutations.

In addition, the researchers identified vaccine distribution as a “public goods problem,” given that the optimal global vaccine allocation may differ from the nation’s preferred allocation, but each country has a vested interest in lessening the potential for novel strains to emerge.

In the University’s press release on Aug. 18, senior author Bryan Grenfell, Professor of Ecology and Evolutionary Biology and Public Affairs noted, “Overall, the models predict that sustained elevated case numbers in LARs with limited vaccine availability will result in a high potential for viral evolution.”

While this research is occurring against the backdrop of the emergence of novel COVID-19 strains such as the delta variant, the research did not directly link their findings on the potential for antigenic evolution to a particular strain.“We’re trying to tease apart the key parameters, such as the strength of natural immunity after infection or vaccine-induced immunity on total trajectories,” said Chadi Saad-Roy, one of the co-first authors and a graduate student in the department of ecology and evolutionary biology and the Lewis-Sigler Institute for Integrative Genomics at the University.

Another co-first author, Caroline Wagner, was previously a postdoctoral research associate at the High Meadows Environmental Institute (HMEI). In addition, one of the senior authors of the study, C. Jessica Metcalf, is an Associate Professor of Ecology and Evolutionary Biology and Public Affairs at the University. Metcalf is currently on sabbatical and was not available for comment.

In the Aug. 18 press release, Metcalf noted, “High case numbers in unvaccinated populations will likely be associated with higher numbers of hospitalizations and larger clinical burdens compared to highly vaccinated populations.” However, the study found that increased vaccine-sharing would not only result in reduced cases in LARs, but also lessen the clinical severity of infections.

The article also opens the opportunity for future research to be done in the field.

“There’s a number of refinements that can be done to these models,” Saad-Roy said. “It’s opening up a number of potential future avenues to build upon and refine the models.”

The model has additional complexities such as differences in population sizes and transmission rates.

The study builds on two other articles in Science examining various epidemiological dynamics of COVID-19.

The first article, published on Nov. 13, 2020, was entitled “Immune life history, vaccination, and the dynamics of SARS-CoV-2 over the next 5 years.” The research examined potential five-year transmission landscapes depending on a variety of factors such as immunity, vaccination rate and effectiveness, and social distancing protocol.

The second article, “Epidemiological and evolutionary considerations of SARS-CoV-2 vaccine dosing regimes,” published April 23, examined the epidemiological and evolutionary considerations of dosing regimes.

Other University co-authors include Simon Levin, Professor in Ecology and Evolutionary Biology, Rachel Baker, an associate research scholar in HMEI, and Andrea Graham, Professor of Ecology and Evolutionary Biology.

Source: The Daily Princetonian

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