Corona: can you get infected twice?

Christiane Fux studied journalism and psychology in Hamburg. The experienced medical editor has been writing magazine articles, news and factual texts on all conceivable health topics since 2001. In addition to her work for, Christiane Fux is also active in prose. Her first crime novel was published in 2012, and she also writes, designs and publishes her own crime plays.

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The following applies to many infectious diseases: if a patient has the disease behind them, they are protected from the pathogen for some time or even for life. It is not yet clear whether this also applies to SARS-CoV-2. Hong Kong is currently reporting the first evidence of a second infection with the pathogen. On the other hand, recent studies indicate that longer immune protection is at least conceivable.

Anyone who has had a corona infection hopes to be protected from it for the time being. The question is of crucial importance because without long-term immune protection, herd immunity is not possible even after a long period of time.

Longer immune protection possible

The typical immune reactions also occur with a SARS-CoV-2 infection. If the virus has managed to penetrate body cells, the immune system forms what are known as T killer cells, among other things. You are specifically geared towards the new pathogen. They destroy body cells in which the virus has lodged. In addition, B lymphocytes (B cells for short) produce antibodies that bind to the pathogen and thus render it harmless.

The antibodies against the virus initially continue to patrol the blood. For the time being, this makes it difficult or even impossible for the pathogen to trigger a new infection. However, studies have shown some time ago that they disappear from the blood relatively quickly - or in some people were not even detectable in the first place. This raised doubts about long-term immune protection.

Antibodies detectable for months

Recently, however, studies have also been published that paint a somewhat different picture. A group led by US immunologist Deepta Bhattacharya was able to show that the production of certain antibodies against Sars-CoV-2 persists for at least three months. The study has not yet been reviewed by experts or published in a specialist journal.

Canadian researchers also report in such a preprint study that at least certain antibodies, so-called IgG antibodies, are relatively stable in the blood and saliva for longer than 100 days. It is unclear how many antibodies are actually needed for effective protection.

Memory cells give cause for optimism

A study published in the specialist journal “Cell” ensures that so-called T memory cells are built up on a large scale in the event of a corona infection.

In the event of a new infection, they react quickly and can build up a specific defense squadron of killer cells and B cells comparatively quickly. In addition, researchers write in "Nature" that they found specific T cells in all of the samples they examined from recovering Covid patients.

A preprint study from the USA also came to the conclusion that people who had a mild course of the disease had persistent memory cells in their blood.

Detected double infection?

However, Hong Kong researchers only reported on Monday that they could for the first time have detected another corona infection in a patient who had already recovered for a long time.

According to this, a man was infected with the virus in the spring. After he had recovered from the corona infection, the virus was detected again four months later after a trip to Spain in August. Genetic tests have shown that there are different variants of Sars-CoV-2. That speaks against a flare-up of the first infection.

Maria van Kerkhove, Covid-19 Commissioner of the World Health Organization (WHO), referred to the press release at a press conference and said: "As we understand the press release, this could be an example of reinfection." However, this has not been clearly proven .

Is it easier for a second infection?

It could be that the course is at least easier with a second infection - or that you are no longer contagious, says Carsten Watzl, Secretary General of the German Society for Immunology.

Watzl emphasizes that people naturally want to know whether or not they are protected after a corona infection. This question could be particularly relevant for hospital staff who deal with infected people. For the course of the pandemic, the question of immunity is not relevant, says Watzl.

"The last word has not yet been spoken."

It is unclear what the previous results on immunity after infection mean for the effectiveness of a vaccination. It will be a while before there is a really clear picture of immunity. The study situation is still diffuse, sometimes contradicting one another. Or to put it in Liebert's words. "The last word has not yet been spoken."

Studies that keep an eye on people after an infection for years have so far been lacking - after all, the virus has only been known for about eight months.

(CF / dpa)

Tags:  laboratory values travel medicine menshealth