Session S15 - Mathematics of Planet Earth

Wednesday, July 14, 17:30 ~ 17:55 UTC-3

Optimizing COVID-19 second-dose vaccine delays saves ICU admissions

Claudia Sagastizábal

Unicamp, Brazil   -   This email address is being protected from spambots. You need JavaScript enabled to view it.

The current production level of coronavirus vaccines is setting the rhythm for the deployment of vaccination campaigns. As most vaccines require two doses, delivery delays reduce the initial impact on transmission and increase the risk of the emergence and spread of new SARS-CoV-2 strains. Governments consider delaying the second-dose to increase the number of first-dose vaccinated individuals. Such a delicate decision depends on the first-dose efficacy and the time window of the second-dose. To assess the desirability of stretching doses, we propose an optimization model based on an extended SEIR dynamics that find the best gap between doses. Robot Dance is a mathematical optimization platform developed for intervention against Covid-19 in a complex network. In the considered instance, the model infers the lightest social distancing profile required from the society while deploying vaccines. Such optimal strategy is chosen among multiple scenarios of postponement of the second-dose, keeping the intensive care unit (ICU) use below maximum capacity by means of a probabilistic constraint. Our results show that the decision depends strongly on whether the vaccine blocks infection or alleviates symptoms. With a vaccine-like AZD1222 with two-dose efficacy of 82.4%, assuming the first-dose efficacy is 55-65% or more and the vaccine blocks infections, the algorithm recommends delaying the second-dose as much as possible. By contrast, if the vaccine only alleviates symptoms, stretching the gap between doses to its maximum time is the best strategy only after the first-dose efficacy is at least 70-75%. Our results show that, when the vaccine blocks infection and the efficacy of the first dose is about 70%, delaying the second-dose saves 400 ICU admissions per million people in 200 days thus leading to a sharp contribution in saved lives.

Joint work with Paulo J. S. Silva (Instituto de Matemática, Estatística e Computação Científica, Universidade Estadual de Campinas, São Paulo, Brazil), Claudia Sagastizábal (Instituto de Matemática, Estatística e Computação Científica, Universidade Estadual de Campinas, São Paulo, Brazil), Luis Gustavo Nonato (Instituto de Ciências Matemáticas e Computação, Universidade de São Paulo, São Paulo, Brazil), Claudio Struchiner (Fundação Getúlio Vargas, Rio de Janeiro, Brazil) and Tiago Pereira (Instituto de Ciências Matemáticas e Computação, Universidade de São Paulo, São Paulo, Brazil).

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