Modelling optimal vaccination strategies against COVID-19 in a context of Gamma variant predominance in Brazil
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2022
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Introduction: Brazil experienced moments of collapse in its health system throughout 2021, driven by the
emergence of variants of concern (VOC) combined with an inefficient initial vaccination strategy against
Covid-19.
Objectives: To support decision-makers in formulating COVID-19 immunization policy in the context of
limited vaccine availability and evolving variants over time, we evaluate optimal strategies for Covid-
19 vaccination in Brazil in 2021, when vaccination was rolled out during Gamma variant predominance.
Methods: Using a discrete-time epidemic model we estimate Covid-19 deaths averted, considering the
currently Covid-19 vaccine products and doses available in Brazil; vaccine coverage by target population;
and vaccine effectiveness estimates. We evaluated a 5-month time horizon, from early August to the end
of December 2021. Optimal vaccination strategies compared the outcomes in terms of averted deaths
when varying dose intervals from 8 to 12 weeks, and choosing the minimum coverage levels per age
group required prior to expanding vaccination to younger target populations. We also estimated dose
availability required over time to allow the implementation of optimal strategies.
Results: To maximize the number of averted deaths, vaccine coverage of at least 80 % should be reached
in older age groups before starting vaccination into subsequent younger age groups. When evaluating
varying dose intervals for AZD1222, reducing the dose interval from 12 to 8 weeks for the primary sched ule would result in fewer COVID-19 deaths, but this can only be implemented if accompanied by an
increase in vaccine supply of at least 50 % over the coming six-months in Brazil.
Conclusion: Covid-19 immunization strategies should be tailored to local vaccine product availability and
supply over time, circulating variants of concern, and vaccine coverage in target population groups.
Modelling can provide valuable and timely evidence to support the implementation of vaccination strate gies considering the local context, yet following international and regional technical evidence-based
guidance.
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Modelling, COVID-19, Immunization, Vaccines
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FERREIRA, Leonardo Souto et al. Modelling optimal vaccination strategies against COVID-19 in a context of Gamma variant predominance in Brazil. Vaccine, Amsterdam, v. 40, n. 26, p. 6616-6624, 2022. DOI: 10.1016/j.vaccine.2022.09.082. Disponível em: https://www.sciencedirect.com/science/article/pii/S0264410X22012166. Acesso em: 2 dez. 2024.