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- André Biernath
- BBC News Brazil in São Paulo
Credit, fake images
From what is known so far, cases of infection are very rare and most patients who have had COVID-19 have immunity that lasts for at least six months.
Receiving a diagnosis of covid-19 is not easy. After all, the disease is surrounded by uncertainties from a medical and scientific point of view and insecurities from a personal perspective.
Now imagine recovering from the condition and, a few weeks later, suffering symptoms that suggest this infection, such as fever, dry cough, tiredness, and shortness of breath. Then, a new test confirms the suspicion: the coronavirus invaded the body again.
Yes, reinfection can occur and there are a few dozen confirmed cases in the world. The good news is that, based on what we’ve seen so far, this possibility is very rare.
Let’s get to the numbers: according to the Dutch news agency BNO News, one of the only vehicles for collecting global data on this topic, there are currently 26 confirmed cases of reinfection on the planet. Of these, 25 patients recovered well and only one died. The average time between the first and the second episode of covid-19 is 76 days.
The website also estimates that there are 893 other suspected reinfection cases, which still need to be looked at more closely.
In Brazil, the Ministry of Health affirms that these types of episodes have not become official. But there is a study published in September that detected reinfection in a nursing technician from Ribeirão Preto, in the interior of São Paulo. Furthermore, there are about 95 patients with a similar situation who are still under investigation here.
But after all, what is already known about these duplicate covid-19 episodes? And how can they influence the second wave of cases or the effectiveness of vaccines?
To answer these questions, we must first understand how our bodies create immunity against this and other viruses.
Defense activated
By detecting an attacker like Sars-CoV-2, the coronavirus responsible for the current pandemic, our immune system works to fight back and rid the body of the threat. This process is mediated by two cells: B and T lymphocytes.
“B lymphocytes are responsible for producing antibodies, the immunoglobulins that we know by the acronym IgG, IgA, IgM …”, explains Dr. João Viola, president of the Scientific Committee of the Brazilian Society of Immunology.
If all goes well and the patient recovers well, most of the time these defense cells learn to deal with the infection. If the coronavirus tries to attack the body a second time, simply release these antibodies (such as IgG and IgM) to neutralize the danger.
T lymphocytes are responsible, among other things, for identifying cells that are infected with a certain pathogen. They orchestrate a real counterattack to protect us. However, his performance against Sars-CoV-2 still continues with some unanswered questions.
This immune action seems to work well in the vast majority of those affected by the coronavirus. If we consider that another 63 million people have already suffered from COVID-19 and only 26 have been confirmed and documented to have had the disease twice (according to the most up-to-date figures), it is not an exaggeration, at least for now, to say that the risk of a second episode is very rare.
Credit, fake images
The production of antibodies (represented in the image in these Y-shaped structures) is observed in the vast majority of cases of Sars-CoV-2 infection.
In statistical terms, according to the data available to date, the reinfection rate is 0.000041%. “This is definitely not a frequent event from what we are seeing so far”, evaluates the infectologist Julio Croda, from the Oswaldo Cruz Foundation (FioCruz).
In relation to the second wave of the pandemic that hits Europe, the United States and Brazil, reinfection is therefore not a relevant phenomenon. According to the information available to date, the vast majority of those affected in recent weeks were vulnerable and contracted the virus for the first time.
But how to explain these confirmed cases (or reports) of reinfection?
Inadequate response
“Apparently, reinfection is more likely in those situations in which the first episode of covid-19 was mild,” contextualizes infectologist Fernando Bellissimo Rodrigues, professor at the University of São Paulo’s Ribeirão Preto School of Medicine.
Everything suggests that a mild disease with few symptoms generates a weaker immune response. “It seems that the production of antibodies is lower, and that would leave the person predisposed to a new disease after a while”, adds Rodrigues.
There is another possibility that needs to be explored here: instead of a reinfection, isn’t it just a continuation of the first picture, which got better for some time and then relapsed?
To rule out this hypothesis, experts turn to Sars-CoV-2 genetic sequencing. Ideally, have a sample from the first and second diagnoses to compare the viral RNA letters.
If they are absolutely identical, there is a high probability that it is actually a relapse. Now, if the genome is different, then it is easier to bet on reinfection.
“This study is as if we were reconstituting a crime without witnesses. We collected evidence that could favor one or another line of investigation,” compares Rodrigues, who was responsible for detecting the first case of reinfection in Brazil and analyzing 15 other suspected patients.
Validity date
Here’s a key question that still needs to be better understood to complete this puzzle: How long does immunity against covid-19 last?
First of all, it should be noted that Sars-CoV-2 is an absolutely new phenomenon from a historical perspective. The first cases were noticed in the last weeks of December 2019. Therefore, science has little more than 11 months of experience with this virus and its consequences.
“We can say that the immunity lasts six months or a little longer, because that is what we have followed up to now,” says Viola. We do not know, however, if this protection is lifelong (as with other viruses, such as measles) or if it does not persist in the long term (in a scenario similar to influenza, which causes the flu).
This expiration date has direct implications for vaccines. “Will the immunizing agent induce lasting immunity? Or will it need to be reapplied after a certain time?” Rodrigues asks.
Credit, fake images
It is not yet known how long the protection of the vaccine against covid-19 will last. Doses may guarantee immunity for the rest of your life or just for a few months or years
You can see it: there are vaccines that are taken once or several times in life. Others, on the other hand, are effective for a year or a little longer and require booster doses to upgrade protection against a certain virus or bacteria.
You will have to wait a little longer before we have all these answers.
Learnings
Although infrequent, cases of reinfection already leave us some lessons. The most important of these is that not everyone who has had contact with the coronavirus is free from a second episode. Therefore, it is not possible to relax in the recommended measures, such as physical distance, wash hands and wear masks.
After all, although it is a rare phenomenon, we are talking about a potentially lethal disease. “It is essential to maintain as much protection as possible. From the community point of view, we have to set an example and continue with the use of masks and other attitudes. This shows how we care about everyone around us,” says Croda, who is also Professor at the Federal University of Mato Grosso do Sul.
In a scenario of so many mysteries, one thing is certain: Covid-19 affects each individual differently, but overcoming the pandemic depends on the joint effort of the entire society.
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