Am I immune to COVID-19 if I have already had it...

They have some immunity, but how much and how long are big unanswered questions.

There is evidence that re-infection is unlikely for at least three months, even in people with a mild case of COVID-19. That is how long New York researchers found stable levels of protective antibodies in a study with almost 20,000 patients at the Mount Sinai Health System.

Reinfection has been rare so far. Best-known example: Researchers in Hong Kong said a man had mild COVID-19 and was re-infected months later but showed no symptoms. His second infection was discovered through airport tests, and researchers said genetic testing found slightly different strains of the virus.

It is actually proof that the man’s immune system worked the way it should. Very few diseases make people completely immune for life.

The US state of Nevada also saw a similar case. A 25-year-old patient with no previous illness entered the Washoe County community testing station on April 18 with a sore throat, dry cough, and headache. His PCR nasal swab test for COVID-19 came back positive, but he was soon feeling fine again. Then, 35 days later, he was taken to the emergency room, short of breath and with a raging fever, and placed on oxygen support. It became the first confirmed US case of COVID-19 reinfection.

So far there have been only a handful of similar cases worldwide in Belgium, the Netherlands and Ecuador. Experts say it is too early to draw any full conclusions from such a small workforce. However, the prospect of catching COVID-19 again – and getting even sicker the second time – could have a significant impact on how governments navigate the path out of the pandemic.

Reinfections, in particular, can make the notion of herd immunity – that is, a sufficiently high percentage of people who eventually become immune to COVID-19 – unrealistic.

“Reinfection cases mean that in some people the immune response is insufficient to protect them from infection or disease,” Akiko Iwasaki, professor of immunobiology and molecular, cell and developmental biology at Yale University, told AFP.

“Reinfections from SARS-CoV-2 (the virus that causes COVID-19) mean that the immunity acquired through natural infection is not perfect.”

Researchers documenting the patient’s case in Nevada offered a number of possible explanations for how he might have gotten sick twice. He may have been exposed to a very high dose of the virus the second time, causing a more acute response. Alternatively, it could be a more virulent strain of the virus.

Will the reinfected be silent spreaders?

Antibodies are only part of the body’s defenses and naturally decrease over time. And normally “memory” immune cells can identify germs they have previously encountered so that they can fight them better the second time. This can help make repeated infections less severe.

Scientists are studying how the other parts of the immune system come into contact with the coronavirus.

It is not known whether people who have been re-infected but do not show symptoms can spread the virus to others. Because of this, health officials say that even people who have recovered from COVID-19 must wear a mask, keep their distance, and practice good hygiene.

Will reinfection be frequent?

Frederic Altare, director of immunology at the Inserm Research Center for Oncology and Immunology in Nantes-Angers, said there is currently little evidence that COVID-19 reinfection is a “major problem” given the low number of cases.

“With the number of people infected, there are only about a dozen proven reinfections – that’s not a lot,” he told AFP. However, others said it was difficult to accurately measure reinfection numbers as relatively little testing was done during the first wave this spring.

In other words, many people could theoretically have been infected in March or April and have remained asymptomatic only to test positive later in the year when they were re-infected, but this time with symptoms.

According to Jeffrey Shaman, professor of environmental health sciences at Columbia University’s Mailman School of Public Health, the main obstacle to establishing reinfection numbers is that SARS-CoV-2 is epidemiologically brand new, unlike other human circulating coronaviruses.

“The world has only looked at it for a few months,” he told AFP.

“We don’t know whether (reinfection) will be as frequent or as likely as the initial infection.

“It’s really important to understand what this virus will ultimately do and how difficult it will be to make a universal vaccine,” Shaman said.

How about other viruses?

While it’s hard to say how widespread or how common COVID-19 reinfections will be, scientists can search for similar viruses for clues.

Lia van der Hoek, an expert in coronaviruses at the Amsterdam UMC, has been studying the pathogens for decades. She was the lead author of a paper published in Nature Medicine last month that examines the four other coronaviruses that can catch people.

The study recorded 10 healthy people over a period of more than 30 years and found that patients were infected with the virus multiple times. One patient was infected 17 times during the study period.

“COVID-19 will likely behave the same way,” she told AFP.

The shaman also examined the circulation of other coronaviruses after 12 healthy people and proved that they could be re-infected a second time. He said evidence from other respiratory viruses suggests widespread reinfections from COVID-19 are by no means impossible.

Is herd immunity dangerous?

On Monday, Dutch researchers published the case study of an 89-year-old woman who died after contracting COVID-19 twice. She had been treated for cancer and her immune system was damaged, making her more susceptible to serious infections.

As the world looked for a vaccine, Iwasaki said that any ultimately safe and universal vaccination would have to produce higher levels and longer lasting immunity in humans than natural infections.

“Fortunately, some vaccine candidates seem to be doing just that.” But reinfections likely meant that any hope of naturally occurring herd immunity was “impossible,” Iwasaki said.

“From what we know about COVID-19, it would be too dangerous to attempt herd immunity through natural exposure to this virus as it can be fatal or harmful in people of all ages.”

There is also a dire prospect of so-called antibody-dependent amplification – when antibodies actually worsen subsequent infections, such as dengue fever.

While there is currently no evidence of COVID-19, Shaman said he doesn’t know of anyone who can rule it out.

Pandemic to endemic: will COVID-19 ever go away?

While many governments base their hopes of a full economic recovery on a vaccine, Van der Hoek said there may never be a single, fully effective, fail-safe COVID-19.

“The problem with coronavirus antibodies is that they decrease so quickly and you can get infected again with the same strain,” she said.

“So it could be that you need repeated (COVID-19) vaccinations all the time,” she said, adding, “This one will never go away. There is no way we can get rid of them. She will stay with us forever. ”The rest of humanity. ”