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COVID-19 models

Sept. 25, 2020: COVID-19 model on effectiveness of global vaccination strategies

Which global distribution strategy for a hypothetical COVID-19 vaccine will save the most lives?

UF professors Ira Longini, Ph.D., and Natalie Dean, Ph.D., recently contributed to a modeling study that estimates the effectiveness of two different global distribution strategies for a hypothetical COVID-19 vaccine. In one scenario, countries work together, and in the other wealthy countries focus only on their own citizens.

Longini and Dean are both faculty in the department of biostatistics in the UF College of Public Health and Health Professions and the UF College of Medicine. Longini is a renowned expert in designing vaccine trials and vaccination strategies, as well as modeling infectious disease transmission; he works frequently with the World Health Organization and the US Centers for Disease Prevention and Control. Dean is a biostatistician specializing in the statistical analysis of infectious disease outbreaks such as Ebola, Zika and HIV. Her work also focuses on designing vaccine trial strategies for emerging pathogens and the pair often collaborate.

The new study was led by researchers at Northeastern University’s Laboratory for the Modeling of Biological and Socio-technical Systems (also known as the MOBS Lab). It is not yet peer-reviewed but is available online as a pre-print. The study results are also featured in the Gates Foundation 2020 Goalkeepers Report: COVID-19 A Global Response.

The research team analyzed what would happen if countries either cooperated or were selfish when distributing 3 billion doses of a hypothetical COVID-19 vaccine across the world. In the cooperative scenario, the doses are distributed proportional to each countries’ population. In the selfish scenario, the wealthiest countries snap up the first 2 billion doses for their own citizens.

The model assumes that the vaccine is effective after two weeks. But because no one knows what the future course of the pandemic may be, the researchers ran simulations assuming that a vaccine was available on March 16, 2020 and they analyzed how its availability and allocation would have affected the approximately 900,000 COVID-19 deaths recorded globally by September 1. By simulating “what if” scenarios, the researchers compared the effectiveness of the two allocation strategies against what unfolded in reality when no vaccine was available.

Bar graph showing the effects of nations cooperating or not to distribute a vaccine

Figure courtesy of the authors.

Their model showed that if nations were to cooperate to distribute a vaccine with 80% efficacy, it would have reduced actual COVID-19 related deaths by 61%, while the selfish scenario would have averted only 33% of these deaths. (See graph above.) When the vaccine’s efficacy was lowered to 65%, the model estimates that the cooperative and selfish allocation strategies would have resulted in 57% and 30% fewer deaths, respectively.

The research shows that when nations cooperate to distribute a vaccine, they can save far more lives globally than if wealthy nations were to focus only on their own citizens.