19 – What is known so far about reinfections and immunity against the coronavirus


Recently, there have been several reports of single people being infected with the new corona virus for the second time. What does this say about immunity and vaccine research?

What is known about coronavirus reinfections?

Since the novel coronavirus has been circulating around the world, he has been puzzled if and when anyone could contract Covid-19 again after a coronavirus infection – an important question as well as regards vaccine requirements. Already in the spring, some cases became known where the coronavirus could be detected again a few weeks later after a negative test. In these cases, the researchers hypothesize different scenarios: the virus may have remained in the body and the disease manifested again later – or the tests were misleading because dead viral material could be detected.

There have now been reports of some patients – for example in Belgium, the Netherlands, the United States, Ecuador and Hong Kong – who contracted the virus again weeks or months after being infected with Sars-CoV-2. These are definitely reinfections: as Dutch virologist and government consultant Marion Koopmans announced, the Dutch patient’s genetic code – a sort of fingerprint of the virus – differs significantly from the first in the second infection. This speaks against a flare-up of the first infection, he told Dutch radio.

Genetic changes in the fingerprint

Another genetic signature was found in the new Belgian patient. She became ill again three months after her first infection. Shortly before, the University of Hong Kong reported that a man was re-infected after four and a half months: different virus sequences were found in him than the initial infection. It was the same with a man in Nevada and one Ecuadorian, as reported by researchers from both countries.

How does a reinfection work?

There are no research findings on this so far, as only these three reinfection cases have been reliably documented. In the case of the Hong Kong man it is known that, according to the university, he did not show any symptoms with the second infection. In the case of the patient in Belgium, virologist Marc Van Ranst speaks of mild symptoms. In the Netherlands it is an elderly patient with a weak immune system, the details of the course of the disease are not known. It could be that the course is at least easier with a second infection – or that you are no longer contagious, suspects Carsten Watzl, general secretary of the German Society of Immunology.

Individual cases from the United States and Ecuador currently speak out against this. The 25-year-old American initially tested positive for SARS-CoV-2 in mid-April after milder cold and diarrhea symptoms. At the end of May he was tested positive again – this time with fever, headache and cough, and he also had to be ventilated at times. The Ecuadorian man had only mild symptoms when he was first infected in May, and in August the disease was moderately severe.

How long are you immune to after a corona infection?

This question is still largely unanswered. The Dlf “Research News” program reports on new investigations from Harvard Medical School and the University of Toronto that focus on antibodies to the coronavirus. More than 300 infected people were screened for studies. The result: the antibodies were detectable in the blood and also in the saliva of most infected people. The researchers found the greatest amount of antibodies in the patients they examined two to four weeks after infection. The amount of antibody then decreases.

After three months, the antibodies were still present in almost all infected people and in some even after six months, albeit at lower concentrations.
However, it is difficult to get an answer to the question of whether and how long immune protection persists. In addition to antibodies, other factors such as the overall strength of the immune system, which varies from person to person, play an important role in protecting against the pathogen. It is still possible that the duration of immunity differs from person to person, as the Robert Koch Institute states.

No antibodies in people with known infection

The response after natural immune protection is made more difficult by the fact that in some people who have been shown to be infected, no antibodies are found, as a study from the University Hospital of Jena shows. In the former quarantine Corona Neustadt am Rennsteig, it was not possible to detect antibodies against the pathogen in about half of the infected. A study by the Lübeck health department also concluded that only 70% of infected people had developed antibodies, while 30% did not.

What role do helper T cells play in defense?

But it’s not just antibodies that fight infections. The so-called helper T cells also play an important role, as they can remember for years which pathogens the body has successfully fought. However, tests on these immune cells are significantly more complex than antibody tests, as Gerard Krause of the Helmholtz Center for Infection Research told Deutschlandfunk.

In a small study, researchers from Stockholm’s Karolinska Institute tested blood samples from 2,000 people in the Swedish capital for evidence of T-cell immunity to SARS-Cov-2. They saw that some people did not have antibodies, but still showed immunity to T lymphocytes, especially people who only had very mild or hardly detectable symptoms. The actual percentage of people who have already had a corona infection and are likely immune for the time being may therefore be higher than antibody studies suggest. This too has recently been disclosed in relevant studies.

What does this mean for vaccine development?

According to our research group, when we talk about an immune reaction in vaccination studies, we refer to the production of antibodies. It is not clear from what amount an immunity is achieved and for how long it lasts. Furthermore, it is only so far clear to the Oxford University vaccine candidate that the vaccine also produces suitable T memory cells, but this would be quite relevant for long-term immunity. The DLF Research News editorial team gathered information on the state of vaccine research here.

What are the benefits of antibody plasma treatment?

In the United States, treatment of Covid 19 patients with plasma from already cured patients is now allowed through an emergency permit. There are antibodies in the blood plasma that are supposed to help sufferers, a procedure that has been practiced for over a century. So far there have been indications regarding Covid-19 that seriously ill patients survive somewhat more often on the administration of plasma with antibodies than without. The results are unclear, because patients usually received other drugs in addition to plasma. Official approval of the treatment is therefore still pending in the United States. Critics accuse US President Trump of initiating emergency approval mainly due to the presidential election campaign.

DLF scientific correspondent Volkart Wildermuth has gathered more information on immunity to the novel coronavirus here.

(Stand: 10.10.2020)

More articles on the coronavirus

We have created a news blog. In view of the large amount of information, this provides an overview of the most important current developments.

Numbers and dates

+ Current developments: Coronavirus data in Germany (as of October 26)
+ Situation in Germany: What does the rapid increase in new infections and the incidence value mean? (Status: 22/10)
+ Classification: what numbers do we mention on coronavirus and why (as of: 22/08)

Test and protection

+ Coronavirus test: when, where and how? (As of: 28.09.)
+ Corona infection: how reliable are the tests? (Status: 08.10)
+ Treatment: this is how far research on coronavirus vaccines is (as of 20 October)
+ Remdesivir and Co: How far is the search for drugs against Covid-19? (Starting October 16)
+ Infection: what we know so far about reinfections and coronavirus immunity (as of 10.10.)
+ Hospitals: What the rise in corona infections means for them (from 15 October)

Contagion and transmission

+ Transfer: what role do aerosols play (as of 10.10.)
+ Surfaces: how long does the coronavirus last (from 12 October)
+ Face Masks: What You Should Know About Protective Masks (as of: 24.09.)
+ Autumn: What to do when the crown and flu wave collide (starting October 14)
+ Excess Mortality: How Deadly Is Coronavirus Really? (Status: 10.10.)
+ “Superspreader Events”: when demos, celebrations and events become a problem (starting October 13)

Holidays and free time

+ Customs: what remains of the carnival in this session (as of 19.09)
+ Club: what about the opening of the discos (from 03.10.)
+ Travel Notice: Current List of Hazardous Areas (as of 22 October)
+ Overview: Housing bans in the federal states (from 17 October)
+ Repatriated travelers and partygoers: those who are currently increasing the number of German infections (as of 10.10.)

You can also find DLF news on Twitter at: @DLFNews.

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