Analysis: Why Covid-19 may become endemic in Brazil, like dengue or influenza

RIO DE JANEIRO, BRAZIL – More than a year after it began, the covid-19 pandemic is still not showing any indications that it will be over soon. Even less so in Brazil, where its control is precarious, with slow vaccination, a decline in compliance with preventive measures, and the omission of public agents to implement, encourage, control, and supervise compliance with social distancing rules.

Moreover, to make matters worse, new variants of the novel coronavirus have been emerging and spreading across the country. Therefore, while it is difficult to predict, many experts believe that it will extend at least until 2022.

According to epidemiologist Guilherme Werneck, vice-president of the Brazilian Association of Collective Health (ABRASCO) and professor at the Institute of Social Medicine of the Rio de Janeiro State University (IMS/Uerj), the conditions for controlling the epidemic in Brazil are so precarious that it will not end anytime soon.

“There is a shortage of vaccines, lack of organization and leadership, and irresponsibility on the part of public officials,” he criticizes. “Starting with the federal government’s misinformation actions, challenging the efficacy of masks, vaccines, and social distancing, and encouraging the use of ineffective drugs for the prevention and treatment of covid-19. It is possible, although still in a distant future, that the World Health Organization (WHO) will declare the end of the pandemic, but Brazil will still have to deal with unacceptable transmission levels.”

Physician Plinio Trabasso, from Unicamp’s School of Medical Sciences (FCM), also projects that the covid-19 epidemic in Brazil will be long-lasting, mainly because vaccination is not being conducted in a massive, widespread, and concurrent way.

As a result, there is still a large number of people susceptible to the disease in circulation. “For faster control, more people (ideally everyone over 18) need to be vaccinated quickly,” he says. “This creates an immunological barrier to the spread of the virus.”

According to Trabasso, in addition to vaccination, mass testing is needed, to identify potential transmitters and quarantine them, and more social distancing.

“These are the most effective ways to contain the spread of covid-19,” he explains. “Of course, hand hygiene and mask wearing are also important, but these are individual measures, whereas immunization and testing are state actions.”

The absence of effective epidemiological surveillance is another problematic and worrisome aspect of the pandemic in the country. “Brazil has financial resources and trained professionals to develop an efficient process of identifying cases, through testing and active search, and quarantine for all people infected, with financial support to ensure that the population will not lose income,” says health physician Maria de Fátima Siliansky de Andreazzi, professor of Political Economy of Health at the Federal University of Rio de Janeiro (UFRJ).

She says that in Europe, should someone be diagnosed with Covid-19 aboard a plane, for instance, they will track everyone who was close by, test and isolate all passengers. “In Brazil, in the case of Manaus, with the new strain detected, flights were not interrupted and furthermore, the Ministry of Health moved infected patients to other states,” she criticizes.

The problem is that despite vaccination, the novel coronavirus is not expected to vanish, unlike Sars-Cov-1, which caused the SARS epidemic.

“Some vaccines are showing excellent protection to prevent severe forms of covid-19 (most, over 90%). However, in some people they fail to prevent infection and, in many cases, the onset of symptoms,” explains physician Fredi Alexander Diaz Quijano, from the Department of Epidemiology, Faculty of Public Health, University of São Paulo (FSP-USP).

According to him, the actual impact vaccines will have in reducing transmission is uncertain, but indirect evidence suggests that they will not completely eliminate covid-19. One of the reasons for this is that new variants may eventually manage to escape the vaccines – and we may need to be vaccinated against the coronavirus as often as we are against the flu, for instance.

Given all this, it is very likely that the virus will remain in circulation. “It will not cause severe illness in the vast majority of vaccinated people, but for susceptible groups who have not been immunized (for whatever reason), there will still be a risk of outbreaks of severe cases and deaths.”

In other words, Covid-19 could become endemic, like AIDS, dengue, influenza, malaria and tuberculosis. “Endemics are situations in which the incidence of the disease is not as high, but it lasts a long time, and may suffer variations, related to the seasons, for instance,” explains physician Marcelo de Carvalho Ramos, full professor of Infectology at Unicamp’s FCM.

“An endemic infectious disease is one that has achieved a certain balance in its reproduction rate,” answers Quijano. “That is, when each contaminated person passes that condition to (on average) one other. This is what is known as the effective reproductive rate (R), which is the average number of new infected people that someone with the virus directly produces. In other words, in the case of endemics the value of R remains close to 1.”

When that number is higher than 1, then the disease progresses rapidly and causes outbreaks (or even major epidemics), as is the case with covid-19, whose R estimate at the beginning of the pandemic was 3. “If that value is much higher than 1 (for instance, higher than 10) it spreads fast, sometimes so fast that people susceptible to it are quickly exhausted,” he explains.

“On the other hand, R values lower than 1 lead to the number of cases progressively decreasing, eventually leading to the eradication of the disease within a community.”

This was the case with SARS: the Sars-Cov-1 virus did not achieve this ability to perpetuate itself. The novel coronavirus has already achieved this evolutionary leap, however. That is why experts believe that Covid-19 will become endemic.

“Sars-Cov-2 has already shown itself capable of mutating, as evidenced by the UK, South African and Amazonas strains,” says Trabasso. “Some of these, or others that will emerge, may allow the virus to escape acquired immunity, either through contact with the ‘wild’ variant or through vaccination.”

According to him, these mutants may cause micro outbreaks, until a new vaccine emerges and a new population contingent develops sufficient immunity to create a new immune barrier. And so on.

“That’s what happens with influenza, for example,” Trabasso explains. “Every year, the population needs to be vaccinated, because mutations can occur in the virus and the immunity acquired by infection or vaccination in preceding years does not guarantee protection against the variant present that year. This is how the novel coronavirus should behave from now on.”

Werneck points out other aspects that may lead Covid-19 to remain among humans for a long time to come. According to him, virus circulation would only be interrupted with high levels of immunity among the population.

“Our knowledge on immunity to the novel coronavirus is still scarce, particularly on the length of time conferred by infection or by a vaccine,” he explains. “Concurrently, what we know about the efficacy of available vaccines, to date, is that they do not provide effective protection against infection, but rather to the development of clinical and severe forms of the disease.”

In other words, these immunizers protect people because they prevent the development of symptoms and severe forms of covid-19, but they do not prevent them from being infected and eventually transmitting the infection.

“In addition, the vaccines used in Brazil (so far, the Oxford-AstraZeneca and CoronaVac) are about 70% effective, more or less, meaning they are quite effective, but not at optimal levels,” says Werneck. “So even with a high vaccination coverage, we could still have transmission.”

This means that without collective prevention measures, such as the wearing of masks, social distancing and personal hygiene, the vaccine alone will not be able to interrupt transmission. “Add all these problems in a context where vaccines are lacking and a high vaccination coverage of the population will still take time,” Werneck adds.

“We are therefore in propitious conditions to allow the circulation of the virus and the emergence of new variants, all of which contribute to the permanence of the infection among us in an endemic form.”

Source: BBC