How long does immunity to coronavirus last once you catch it? Not much according to new evidence

How long does immunity to coronavirus last once you catch it? Not much according to new evidence

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It is perhaps one of the most pressing questions, but at the same time, one of the least answered of the Sars-CoV-2: How long does immunity last once a person is infected with the virus?

A new study published in the journal Nature Medicine and directed by Chinese scientists, it does not answer the question accurately, but it does give some clues about how long the antibodies last in a person infected.

According to this research, antibodies against coronavirus can last up to three months after a person becomes infected with Covid-19.

In their study, the researchers examined 37 asymptomatic people (who never developed symptoms), in the Wanzhou District of China. They compared their antibody response to that of 37 people with symptoms. The researchers found that people without symptoms had a weaker antibody response than those with symptoms.

In eight weeks, 81% of asymptomatic people saw a reduction in neutralizing antibodies, compared to 62% of symptomatic patients. Also, antibodies dropped to undetectable levels in 40% of asymptomatic peoples, compared to 12.9% of symptomatic individuals, according to the study findings.

Microscopic image of the Sars-CoV-2. PHOTO: Reuters

© National Institute of Allergy and Infectious Diseases – Rocky Mountain Laboratories
Microscopic image of the Sars-CoV-2. PHOTO: Reuters

The study contradicts those who believed that the immunity of the virus would be similar to that of the virus. Sars and the Mers, immunity lasting approximately one year for both coronaviruses. Scientists hoped that the antibodies to the new virus could last at least as long.

However, Howard Bauchner, editor of the Jama scientific journal, it is in line with other coronaviruses. “When you look at history, the common coronaviruses that cause the common cold, reports in the literature indicate that the durability of the immunity it protects ranges from three to six months and almost always less than a year, ”he said during an interview on June 2. “That’s not a lot of durability and protection.”

Research is the first in characterizing the immune response in asymptomatic people.

Herd immunity

The work largely dismisses the herd strategy that many countries proposed in their minute, which in the opinion of Álvaro Lladser, researcher at Fundación Ciencia y Vida, vice president of the Chilean Association of Immunology, “is a very risky alternative, because we do not know if the immunity that the infection gives is long-lasting or protective.”

He says that for such a strategy to work, it may take up to 70 or 80% of the infected population. “In the case of being only 60%, the deceased should 200,000,” he warns.

Although the studio is small, the researchers say they are still learning about key aspects of the virus, including the response of the immune system once a person is exposed, and they insisted on rejecting the possibility of creating so-called immunity passports, for those who have already suffered from the disease.

However, some specialists point out that the end of antibodies in the body does not necessarily mean the end of immunity and that these people can become infected a second time. Even low levels of potent neutralizing antibodies can be protective, like T and B cells of the immune system. That is, the innate ability of the human body to offer protection against foreign pathogens.

Another study conducted in China as well, but still in preprint mode (other scientists’ review is lacking), also concluded that it is unlikely that infected people have protective antibodies against the coronavirus for long periods of time.

For the study, the scientists looked for specific antibodies to the coronavirus in the blood samples of 1,470 patients with Covid-19 in three hospitals in Wuhan, China, the original epicenter of the pandemic.

Previous research pointed out by the authors of this research suggests that the antibodies that constitute the first line of defense against the coronavirus are detectable around seven days after a person is infected, whereas virus-specific antibodies can take around two weeks.


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