Fabio Mazzitelli, from ACI Unesp*
A scientific paper written by researchers of the BR COVID-19 Observatory, with the participation of scientists from Unesp, Fiocruz, Unicamp, UFABC and USP, presents a thorough statistical analysis to measure, in figures, the fundamental role played by mass vaccination against COVID-19 and the efficacy of this sanitary strategy implemented amidst much misinformation and hesitancy during the sanitary crisis installed in Brazil. The analysis described in the study shows that in estimates considered conservative by the authors, the vaccines against the disease caused by coronavirus Sars-CoV-2 saved from 54,000 to 63,000 lives of people 60 years or above between January and August 2021. In the same period, vaccination also avoided from 158,000 to 178,000 hospitalizations of elderly people in Brazilian hospitals. The paper titled Estimating the impact of implementation and timing of the COVID-19 vaccination program in Brazil: a counterfactual analysis, which will be available online after November 21, is one of the highlights of its issue of the prestigious The Lancet Regional Health Americas, of Elsevier.
Although vaccination was kicked off in January, immunization in Brazil scaled up very gradually: 250,000 doses per day was the number achieved between February and March; the milestone of 500,000 daily doses was reached between April and May, and the rhythm of 1 million doses per day only became a reality in June 2021. If the vaccination rhythm of the immunization campaign had been, from the beginning, the same observed after eight weeks, for instance, the number of elderly deaths by the virus could have been from 40% to 50% smaller than the rate observed at the peak of the Gamma variant of concern (VOC) of Sars-CoV-2, according to the study. Estimates indicate that another 47,000 elderly lives could have been saved, and approximately 104,000 hospitalizations could have been avoided, in a scenario of more acceleration of immunizations. The dissemination of the Gamma variant was marked by a dramatic sanitary crisis in Manaus, capital of the state of Amazonas, in January 2021, and led to more extreme attitudes by some government agents, such as the lockdown decreed in February in the city of Araraquara, in the state of São Paulo.
To get to these figures, the researchers focused on the first months during which the vaccines began to be applied in the country and on the elderly, the first age group to complete the vaccine scheme through the immunization program. As they traced the curve of deaths and hospitalizations by Covid-19 among the Brazilian population and overlapped it with a similar curve in groups of elderly people who were being vaccinated by the Unified Health System (SUS) in 2021, the positive correlation between vaccination and the prevention of death and severe cases was evident: the more vaccination coverage grew amongst the elderly, the greater the reduction of COVID-19 impact in these groups of people 60 and up.
With the contrafactual analysis model built, assuming that immunization is directly related to the decrease in severe cases and deaths and that exposure to infection by Sars-CoV-2 was the same for all age groups over the period under analysis, the study built different scenarios in order to compare them with a hypothetical scenario of complete absence of immunization. It was then possible to observe a reduction of approximately 35% in hospitalizations of elderly people between January and August 2021. Considering that each hospitalized person during the pandemic resulted in an average cost, in Brazil, of US$ 12,000, preventing between 158,000 and 178,000 hospitalizations amounted to something between 1.9 and 2.1 billion dollars not spent by the public health system, an impact which the researchers compared, in the paper, to the US$ 2.2 billion invested in vaccines in the period under analysis, up to August 2021.
“Our model is based on the premise that the behavior of the epidemic was the same in the different age groups. Not in the sense that they had the same number of cases, but that they have the same up and down behavior, more or less during the same period of time. If we consider an age group that is not being vaccinated at a given moment and compare it with an age group that is receiving the vaccine, there is a difference in this behavior. The number of severe cases among the elderly began to decrease, while the number of hospitalizations among younger people began to go up. This behavior is due to vaccination in that population. This is the explanatory variable for the difference between these two age groups”, says Leonardo Souto Ferreira, first author of the paper and researcher of the Theoretical Physics Institute (IFT) of Unesp. “The fact that vaccines made a difference is indisputable.”
More lives could have been saved
The study goes beyond the mere quantification of the number of lives saved by vaccines in Brazil. The analysis made by the researchers built two other scenarios to estimate how many lives could have been saved and how many hospitalizations could have been avoided if mass vaccination against COVID-19 had begun at a more accelerated rhythm, such as what took place four and then eight weeks after the initial vaccination week, on 18 January 2021. These scenarios are described as a moderate and high acceleration of immunization, respectively.
“Although we could not avoid the emergence of the Gamma variant, as it appeared in November and vaccines were only made available in January, a rapid vaccination campaign could have considerably reduced the peak of hospitalizations and deaths, especially among the elderly and first and foremost in the states in which Gamma took a while to arrive”, states researcher Flávia Maria Darcie Marquitti, of the Gleb Wataghin Physics Institute and of the Biology Institute, both part of Unicamp.
The study emphasizes that, in mid-2021, immunization of the Brazilian population played a “decisive role” to prevent a new severe wave of hospitalizations and deaths when another variant of concern, Delta, began to spread through the country and become the predominant strain. At that point, vaccination had already sped up, as it had in previous vaccination campaigns, such as the H1N1 flu virus in 2010, when the SUS vaccinated 88 million people in three months.“When Delta came, it found it more difficult to spread”, explains Marcelo Gomes, co-author of the study and a Fiocruz researcher in the field of public health.
The researchers emphasized that the first-generation vaccine against COVID-19 allows our bodies to gather info on a certain virus without the need to go through infection and face the risks involved; it, therefore, avoids the risk of severe disease and death. “This should be made very clear to our population. Vaccines have a tremendous social impact, direct as well as indirect. The smaller the number of hospitalizations, the better we’re able to distribute resources to attend to those who end up having severe disease anyway, or who suffer from other conditions”, says Gomes.
Although the study focuses on the population above 60 years of age, for the researchers it also converses with the issue of children’s vaccination. Approved in the second half of December 2021, vaccination of children from 5 to 11 began in the second half of January 2022, coinciding with the peak of the Omicron variant. “If we had managed to begin vaccinating children as early as December, we would have had an extremely positive outcome for the public between 5 and 11”, said Gomes. “Vaccination of children has been slow going because a series of unfounded questionings have been created regarding the safety of the vaccine, generating what we call vaccination hesitancy: part of the population is unsure whether the vaccine is safe and effective”, he added.
Since the beginning of the pandemic, in March 2020, COVID-19 has caused the deaths of about 689,000 people in Brazil.
*With the collaboration of Cristina Azevedo (Fiocruz News Agency)