Ascientific article by members of the COVID-19 BR Observatory presents a refined statistical analysis demonstrating in numbers the fundamental role played by mass vaccination against COVID-19 and the effectiveness of this public health strategy, which was implemented amid much disinformation and hesitation in Brazil during the pandemic. The authors are scientists affiliated with São Paulo State University (UNESP), Oswaldo Cruz Foundation (FIOCRUZ), the State University of Campinas (UNICAMP), the Federal University of the ABC (UFABC) and the University of São Paulo (USP).
The results of the analysis show that vaccination against the disease caused by novel coronavirus SARS-CoV-2 saved between 54,000 and 63,000 lives of people aged 60 and over between January and August 2021, in estimates considered conservative by the authors. In the same period, vaccination also averted between 158,000 and 178,000 hospitalizations of COVID-19 patients in this age group. The paper, entitled “Estimating the impact of implementation and timing of the COVID-19 vaccination program in Brazil: a counterfactual analysis”, is available from November 21 on the “Online First” website of the prestigious journal The Lancet Regional Health Americas, published by Elsevier.
To obtain these numbers, the researchers focused on the first few months after the start of COVID-19 vaccine rollout in Brazil and on the over-60 age group, the first to complete the vaccination program according to the official calendar. They plotted two curves: deaths and hospitalizations due to COVID-19 for the Brazilian population, and deaths and hospitalizations for the over-60s who were vaccinated by the SUS (Brazil’s public health service), in 2021. Juxtaposition of the two curves clearly showed a positive correlation between vaccination and prevention of severe cases and deaths. The impact of the disease on the over-60s decreased as vaccination coverage of this age group increased.
They then constructed a model in which vaccination correlated directly with a fall in severe cases and deaths, and exposure to infection by the virus was assumed to be the same for all age groups throughout the period analyzed, simulating counterfactual scenarios without vaccination and with faster vaccine rollout. The results showed a reduction of approximately 35% in hospitalizations of over-60s in January-August 2021. Furthermore, considering a mean cost of US$12,000 per patient per hospital stay during the pandemic in Brazil, averting 158,000-178,000 hospitalizations would have saved the SUS US$1.9 billion-US$2.1 billion, which is equivalent to the amount Brazil invested in vaccines in the same period (US$2.2 billion).
“Our model assumes the behavior of the epidemic was the same in all groups, not in the sense that they had the same number of cases but that the numbers rose and fell at about the same time. If you take an age group that isn’t being vaccinated at a particular time and compare it with a different age group that is being vaccinated, then this behavior is different. Severe cases among the elderly begin to fall, while hospitalizations among younger people continue to rise. The difference is due to vaccination. That’s the explanatory variable for the difference between these two age groups,” said Leonardo Souto Ferreira, first author of the article and a researcher at UNESP’s Institute of Theoretical Physics (IFT). “The fact that the vaccines made a difference is indisputable.”
More lives could have been saved
Beyond quantifying the lives saved by vaccines in Brazil, the researchers constructed two other scenarios to estimate the lives that could have been saved and the hospitalizations that could have been averted if vaccine rollout had initially been as fast as it was four weeks and eight weeks after the start of mass vaccination on January 18, 2021, calling the scenarios moderate acceleration and high acceleration respectively.
In actual fact, vaccine rollout began in January and picked up speed gradually, rising from 250,000 doses per day in February-March to 500,00 doses per day in April-May and 1 million doses per day in June 2021. If rollout had started at the pace seen eight weeks later, for example, the number of deaths of over-60s could have been 40%-50% lower than the number recorded at the peak of the wave caused by the gamma variant of concern (VOC), according to the article. A further 47,000 lives could have been saved and 104,000 hospitalizations averted if the initial pace of rollout had matched the high acceleration scenario (equal to the pace four weeks from the start of rollout). The spread of the gamma variant caused a dramatic health crisis in Manaus, the capital of Amazonas State, in January 2021, and led some public agents to take extreme measures, such as the lockdown ordered in February in the city of Araraquara (São Paulo State).
“We couldn’t have averted the emergency caused by the gamma variant, since it was first detected in November and vaccine rollout started only in January, but a faster pace of vaccination would have considerably reduced the peak in hospitalizations and deaths, especially among the elderly and in regions of Brazil not reached until later by the variant,” said Flávia Maria Darcie Marquitti, a researcher at UNICAMP’s Gleb Wataghin Institute of Physics and Institute of Biology, and second author of the article.
Another point highlighted in the article is that vaccination played a “decisive role” in mid-2021 by averting a new wave of hospitalizations and deaths when the delta variant began spreading throughout Brazil. Delta eventually became predominant. By then, vaccine rollout had gathered speed and was proceeding as fast as in previous campaigns, such the one against the H1N1 influenza virus in 2010. In that year, the SUS vaccinated 88 million people in three months. “When the delta variant arrived, it met with more difficulty to circulate,” said Marcelo Gomes, a researcher at FIOCRUZ and a co-author of the study.
Scientists recall that first-generation COVID-19 vaccines averted the risk of severe disease and death by enabling the human organism to “learn” about the virus without being infected by it. “This should be very clear to all Brazilians. Vaccines have a tremendous social impact, both direct and indirect. The lower the number of hospitalizations, the better we can allocate resources to care for those who nevertheless fall severely ill or suffer from other diseases,” Gomes said.
Although the article focuses on the flaws in vaccine rollout for the over-60 age group, the authors reach a similar conclusion regarding the delay in vaccination for children. Approved in mid-December 2021, vaccination of the 5-11 age group began only in mid-January 2022, coinciding with the peak of the wave caused by the omicron variant. Critics of pediatric vaccination contributed to what the authors call “vaccination hesitancy” — doubts on the part of the population regarding the safety and efficacy of vaccines.
Since the start of the pandemic in March 2020, COVID-19 has caused some 689,000 deaths in Brazil.
The authors of the paper published by The Lancet Regional Health Americas received funding from FAPESP, CAPES, CNPq, FAPERJ and Inova FIOCRUZ.