How likely are you to get reinfected from COVID-19? What is known about having coronavirus twice

The world has lived with the new coronavirus for more than eight months;

Vaccines are already in development and some drugs have been found to prevent the death of the most serious patients.

But there remains a lot that is not known about the SARS-CoV2 virus and the disease it causes, COVID-19.

Some of the main questions are: How long does immunity last after the virus is cured?

How likely is it that someone will get infected and sick again?

And what implications does this have for the long-term effectiveness of vaccines?

"It is a very deceptive virus and its immunity is very confusing," immunologist Danny Altman, from London Imperial College, told CNBC.

The doubts are especially urgent after it was made public on Tuesday that

, the first case of a death from apparent reinfection.

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This is what is known, so far.

How likely is someone to get infected again?

In addition to the Dutch case, four people have been found to be re-infected: one in the United States, a case confirmed this week;

a man in Hong Kong;

a person in Belgium;

and a patient in Ecuador.

In those cases, people were affected by a different strain of COVID-19 than the one that initially afflicted them, so it is speculated that the antibodies they had were not effective in protecting against another type of SARS-CoV2 virus or that it viral load was higher because it was another subtype.

So far, doctors indicate that

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"A singular finding does not imply that the phenomenon can be generalized," wrote the scientists who investigated the Nevada man who fell ill again, as published in The Lancet.

In fact, it is not surprising that there are such cases.

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Studies conducted since the 1970s indicate that

and very rarely fatal, according to an article published in the journal Scientific American. 

A similar situation happens with influenza, whose virus mutates constantly and therefore it is convenient to get vaccinated every year to protect yourself. 

With the exception, of course, that there is still no vaccine for SARS-CoV2 and that, unlike common flu caused by other viruses, from which most people recover quickly, SARS-CoV2 has a higher fatality rate. 

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Although scientists ask not to be alarmed at thinking that exceptions make the rule, they also warn that there may be more cases that have not yet been proven.

"So far we have only seen a handful of cases of reinfection, but that does not mean that there are not more, especially since many cases of COVID-19 are asymptomatic," they noted in The Lancet, "for now, regarding the cause of reinfection we can only speculate ”.

What is it like to get sick from COVID-19 again?

Of the few cases of reinfection that have been scientifically proven, in

.

The most serious on the second occasion was that of the patient in the Netherlands. 

However, the woman was 89 years old and suffered from a very rare bone cancer, so scientists who reviewed her death speculated that she could have been affected by cancer treatment, which usually weakens the immune system.

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In the case of Nevada, the symptoms in the reinfection included fever, dizziness and shortness of breath, for which the man required hospitalization, in contrast to the first infection when he only had a cough as well as headache and throat pain.

The Ecuadorian patient who was infected again also went from mild symptoms in the initial infection to moderate in the second infection, which was with another strain, although he did not have to be hospitalized.

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This could be due, according to the scientists from The Lancet, to a

, of

of the infection (ADE or

).

With this disease, those who develop hemorrhagic fever, one of the worst symptoms of dengue, usually already had a contagion of the virus transmitted by mosquitoes.

And there are two reasons, according to medical tests: The first is that the antibodies developed the first time with one subtype do not have the same efficacy with another of the four subtypes.

The second is due to ADE, in which the proteins that normally protect against infection have a counterproductive effect: the antibodies from the first contagion stick to the second virus in an effort to fight it and thus end up making it easier for the molecule to disguise itself as something benign and implant.

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Paul Hunter, from the University of East Anglia, told BBC News that the Nevada case is particularly

, as well as the severity of the second wave of the disease.

The time elapsed between the man's infections in Nevada was six weeks, about 40 days, while the Ecuadorian patient was virus-free for almost three months.

59 days passed for the second contagion of the Dutch woman.

How long does immunity to COVID-19 last?

Those who have developed an immune response, through antibodies called IgM (short-term) and IgG (long-term), maintain it on average between three and six months, according to a study published in June.

Another analysis done in Arizona this week concluded that people recovered from SARS-CoV2 continued to produce antibodies for up to seven months.

However, that is much less than the coronavirus most similar to the current one and that also became an epidemic a few years ago, SARS-1 (severe acute respiratory syndrome). 

Immunity acquired with the presence of antibodies due to this virus, whose epidemic outbreak in 2002 lasted about six months in Asia and with few infections in countries outside that region, lasts about two years. 

Although

"The idea is that even if your antibodies go down, your learned responses don't go away," Vineet Minachery, an immunologist at the University of Texas, told STAT News.

A health professional conducts sponsored coronavirus tests at the Clinica Campesina Martin Luther King Jr. Health Center in Homestead, Florida, in July.

AP

In other words, through memory, the body could again generate enough of the proteins that fight a virus if it registers that SARS-CoV2 wants to infect again.

To

, experts recommend waiting at least three weeks from the start of symptoms.

It is estimated that it takes the human body at least a week to develop antibodies, according to the Centers for Disease Control and Prevention (CDC).

This means that if a person takes the test too early, it could give a false negative result, and there is still a risk of contagion.

How should those who have already recovered from Covid-19 protect themselves?

Scientists in charge of studying human reinfection in Nevada agree: previous exposure to the SARS-CoV-2 virus may

to all people. 

This means that everyone, including those who have already recovered from the disease, must maintain the same measures to prevent reinfection, they indicated in the study published in the medical journal The Lancet.

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That is, wash your hands often, avoid touching your face, keep sufficient distance from other people (at least six feet or two meters), and wear a mask.

It is also important

.

A study conducted in New York City found that 62% of the participants claimed to have had symptoms but never actually had the virus.

"I think literally everyone in New York thinks they have had it. People shouldn't assume that their fever in January was COVID and that they are immune," Dr. Ania Wajnberg told the New York Times.

So whether or not there is a vaccine available and effective after the various phases of current testing, "I think we will

be

" researcher Menachery of the University of Texas told STAT News. 

With information from Scientific American, The New York Times, BBC News, The Lancet and STAT News