After four years of the first covid-19 case in Brazil, it isn’t still possible to identify a pattern for the disease’s behavior. With vaccination, the infection and death rates dwindled dramatically, as well as the seriousness of the disease for most of the population.
Even so, the high rate of transmissibility of the virus and the unpredictability of mutations impose a kind of "precarious equilibrium" on the current epidemiological situation.
Antonio Augusto Moura da Silva, an epidemiologist and professor of the Graduate Program in Collective Health at the Federal University of Maranhão (UFMA, in Portuguese), states that, as the population acquires immunity against the virus, a pandemic may evolve to an “endemic”, that is, when a disease becomes recurring in a region, but without a significant number of cases or deaths.
“The question that emerges is whether we have already reached this balance, that is, whether the situation has evolved into what we call an endemic. Currently, it’s difficult to determine whether or not it was reached. We can’t affirm it. However, every state of equilibrium for all infectious diseases is always very fragile and can be disrupted by anything new," says the professor.
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Moura da Silva says that, although Brazil has not reached this stage, “evidence indicates” the country is walking "in this direction”. However, any balance is precarious, especially if the virus develops a more aggressive mutation. A lethal mutation is a possibility. Mutations are random events, and we can't predict which way they will go," he explains.
This analysis has the same conclusion as Paulo Lotufo, a professor of Internal Medicine at the University of São Paulo Medical School, to whom there isn’t yet a total comprehension of the diseases’ behavior.
He believes that, when dealing with the peaks of COVID-19 cases, it’s “interesting” to compare them to those of influenza. “While the influenza season follows a well-defined time pattern, COVID still did not show this clarity, making it difficult to predict how things will develop. The vaccine, although its contribution to decreasing serious cases and deaths, doesn’t provide for a broad comprehension of covid-19 peaks of cases,” he states.
The current perception is that, as seen in other diseases, there will be more vulnerable individuals, such as those with heat conditions. This dynamic is similar to that of influenza, but the pandemic continues to uncover particularities yet to be totally understood and recorded given the complexity constantly evolving.”
In this sense, the continuous collection and recording of data is crucial due to the constant transformations, contributing to a more complete and efficient understanding in the management of the health system.
Isaac Schrarstzhaupt, an epidemiologist and data scientist at the Rede Análise Covid (Covid Analysis Network, in English), also agrees that there is no pattern to the virus's behavior. He affirms further: he doesn’t know whether it will be possible to identify some pattern due to the virus's high transmissibility.
Schrarstzhaupt says the SARS-CoV-2 is so infectious that it doesn’t depend, for instance, on the seasons, which happens to flu during the winter, when people crowd indoors. In Covid's case, it’s more related to people’s behavior.
For instance, with people adopting prevention measures less frequently, such as the use of protective face masks, there is an increase in the rate of infection, regardless of whether it is winter or summer. As a result, there is a greater chance of the virus mutating and breaking the current control over the disease. "Mutation is a consequence of this high transmission rate because the virus enters the body, enters cells, begins to replicate, and then mutation occurs. A mutation can make the virus completely useless, or smarter. And then it becomes a new predominant variant."
It is mainly through this explanation that Schrarstzhaupt can't see the establishment of a pattern for the disease’s behavior. "For this to happen, the virus would have to lose the capacity to mutate and create so many variants, and the predominant variant that remains would have to be more or less predictable, like influenza. SARS-CoV-2's high mutation rate is what makes me believe it’s unpredictable, at least not in the medium term," says the data.
Vaccination
In addition to being highly infectious, there is a low COVID-19 vaccination rate, especially among children. Researchers emphasize that the current epidemiological situation is significantly different from the scenario seen before the vaccine. Even so, adherence to the latest doses of the vaccine is lower than desired.
According to the Ministry of Health, from the beginning of COVID-19 vaccination in Brazil, on January 17, 2021, until February 6, 2024, 517 million doses were administered to the general public, 6.7 million of which were to children under five years of age.
Up until now, only 6% of children aged between six months and two years and 6.4% of children aged between three and four years have concluded the monovalent vaccination schedule (bivalent coverage is only for children aged 12 and over). The percentage is well below the target of 90% immunization coverage.
"To reduce cases, the population must adopt protective measures. However, to reduce serious cases and deaths, it's only through vaccination. Data show that the pandemic is nowhere near the emergency phase, but it is still serious and responsible for a large percentage of serious respiratory cases," especially among children and the elderly, says the data researcher.
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In 2024, up to the sixth epidemiological week (February 10-16), there were 4,937 hospitalized cases of Severe Acute Respiratory Syndrome (SARS), with 41% (2,020) of them identified as respiratory viruses. Of these, 64% were due to COVID-19. Regarding deaths, 506 SARS deaths were reported in the same period, with 56% (283) identified as respiratory viruses. Of these, 91% were due to COVID-19. The data is from the Ministry of Health's latest Epidemiological Bulletin.
The Ministry's data shows that the elderly are more infected than children. In terms of deaths, the elderly lead.
What does the Ministry of Health say?
Ethel Maciel, Secretary of Health and Environmental Surveillance at Brazil’s Ministry of Health, says the current epidemiological situation is "very different" from when the pandemic was considered a Public Health Emergency of International Concern (PHEIC) by the World Health Organization (WHO). "After vaccination, there was very significant control of the disease. So we've gone from 3,000 people dying a day to an average of between 30 and 50 people a day," she explained.
This year, the COVID-19 vaccine became part of the country’s National Immunization Program (PNI, in Portuguese). The Ministry of Health's priority is children aged between six months and five years old and groups with a higher risk of developing severe forms of the disease: the elderly, immunocompromised people, pregnant and postpartum women, health workers, people with comorbidities, Indigenous people, river dwellers and quilombola people; people in long-term care institutions and their workers, people with permanent disabilities, people deprived of their liberty, teens and young people serving socio-educational measures, workers of the prison system, and people living on the streets.
The secretary highlights that "new strains may emerge. However, in the current scenario – where the Omicron and its subvariants dominate – our vaccines still protect. Our concern lies with those who are falling seriously ill and dying, which are mainly children under the age of two and adults over 70. Therefore, these groups are our current major concern."
"We've already seen a reduction in the number of deaths. Since we have a vaccine and medication, we don't want anyone to die. So one death is already a bad result. But we won't be able to eliminate it overnight. And we never can. We'll always have some remnants. But we're going to work towards an even greater reduction," says Maciel.
Edited by: Rodrigo Durão Coelho
