Abstract
Background: In Brazil, vaccination has always been cutting across party political and ideological lines, which have delayed its start and brought the whole process into disrepute. Such divergences put the immunisation of the population in the background and create additional hurdles beyond the pandemic, mistrust and scepticism over vaccines.Methods: We conduct a mathematical modelling study to analyse the impacts of late vaccination and with slowly increasing coverage, as well as how harmful it would be if part of the population refused to get vaccinated or missed the second dose. We analyse data from confirmed cases, deaths caused by COVID-19, and vaccination in the state of Rio de Janeiro in the period between March 10, 2020, and October 27, 2021. The classical SIR model is extended to consider the effect of vaccination (efficacy, interval between doses, and vaccination rate) and data sets are regularised using Gaussian Process Regression. The model parameter distributions are estimated using Bayesian inference, aiming to obtain credible intervals in the simulations.Findings: We estimate that if the start of vaccination had been 30 days earlier, combined with efforts to drive vaccination rates up, 31,657 (25,801–35,117) deaths could have been averted. Our results also indicate that the slow pace of vaccination and the low demand for the second dose could cause a resurgence of cases as early as 2022.Interpretation: The government’s inaction and lack of a strategic plan to fight the pandemic meant that vaccination started late, leading to thousands of deaths that could have been prevented. Even when reaching the expected vaccination coverage for the first dose, it is still challenging to increase adherence to the second dose and maintain a high vaccination rate to avoid new outbreaks. Funding Information: Carlos Chagas Filho Foundation for Supporting Research in the State of Rio de Janeiro (FAPERJ) and Brazilian National Council for Scientific and Technological Development (CNPq).Declaration of Interests: The authors declare no competing interests.
Highlights
Introduction wordsAs of February 25, 2020, when the first case of infection withSARS-CoV-2 was reported in Brazil, the country has accumulated more than 21·8 million confirmed cases and, on November 17, 2021, Brazil’s death toll topped 610,000
For each particular vaccination rate, we simulate the model for all combinations of proposed scenarios, whose outcomes are shown in figure 3A, concerning the daily number of infected and dead individuals
For an arbitrary vaccination rate, it is clear that starting the vaccination campaign a few days earlier is beneficial both in terms of aflattening the curveso and in terms of suppressing the epidemic
Summary
2) was reported in Brazil, the country has accumulated more than 21·8 million confirmed cases and, on November 17, 2021, Brazil’s death toll topped 610,000. In the first case, immunised individuals are moved into the removed class proportionally to η, the overall vaccine efficacy. The portion of individuals who do not receive the second dose is equal to α and we assume an overall impaired efficacy, given by η. In Brazil, vaccination has always been cutting across party political and ideological lines, which have delayed its start and brought the whole process into disrepute. Such divergences put the immunisation of the population in the background and create additional hurdles beyond the pandemic, mistrust and scepticism over vaccines
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