Recently, there have been several reports of individuals infected with the new corona virus for the second time. What does this say about immunity and the vaccine search?
What is known about redefinitions with the coronavirus?
Since the new coronavirus has been circulating around the world, it has been confusing whether someone can get Covid-19 again after a coronary infection – an important question as well as the requirements for vaccines. As early as spring, some cases became known where the coronavirus could be detected again a few weeks later after a negative test. In these cases, researchers hypothesize different scenarios: the virus could have remained in the body and the disease flashed again later – or the tests were misleading because dead viral material could have been detected.
Now there have been reports from some patients – for example in Belgium, the Netherlands, the USA, Ecuador and Hong Kong – who have caught the virus again weeks to months after being infected with Sars-CoV-2. These are definitely redefinitions: As the Dutch virologist and government advisor Marion Koopmans announced, the Dutch patient’s genetic code – a type of virus fingerprint – is very different from the first in the second infection. That speaks against the flare of the first infection, he said on Dutch radio.
Genetic fingerprint changes
Another genetic fingerprint was found in the newly sick Belgian patient. She was ill again three months after the first infection. Just before, the University of Hong Kong reported a man who was infected again after four and a half months – different virus sequences were found in him than in the initial infection. It was the same with a guy in Nevada and one Ecuadorianer, as reported by researchers from both countries.
How does redefinition work?
To date there are no research results on this, as only these three cases of redefinition have been reliably documented. In the case of the Hong Kong man, it is known that, according to the university, he showed no symptoms with the second infection. In the case of the Belgian patient, virologist Marc Van Ranst talks about mild symptoms. In the Netherlands it concerns an elderly patient with a weakened immune system, details of the course of the disease are unknown. The course may be at least easier with a second infection – or you’re no longer infectious, suspect Carsten Watzl, Secretary General of the German Immunology Association.
Currently the individual cases from the USA and Ecuador speak against this. The 25-year-old American had initially tested positive for Sars-CoV-2 in mid-April after symptoms of cold and milder diarrhea. In late May it was tested positive again – this time with fever, headache and cough, and sometimes had to be ventilated. The Ecuadorian man had only mild symptoms when he was first infected in May, and in August the disease was fairly serious.
How Long Are You Immune After Corona Infection?
This question remains largely unanswered. The Dlf “Research News” program reports on new studies by Harvard Medical School and the University of Toronto that focus on antibodies against the coronavirus. More than 300 infected people were examined for the studies. The result: antibodies were detectable in the blood and also in the saliva of most infected people. The researchers found the highest number of antibodies in the patients examined two to four weeks after infection. Then the size of the antibody decreases.
After three months, antibodies were still present in almost all infected persons, and in some even after six months, albeit at lower concentrations.
However, the question of whether or not the immune defense persists is difficult to obtain. In addition to the antibodies, other factors such as the overall strength of the immune system, which vary 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 Foundation states.
No antibodies in infected people
The answer after natural immune protection is made more difficult by the fact that, in some people who have been proven to be infected, there are no antibodies at all, as a study by Jena University Hospital shows. In the old quarantine town of Neustadt corona for Rennsteig, no antibodies against the pathogen could be detected in about half of the infected. A study by Lübeck’s health department also concluded that only 70 percent of those infected had antibodies, while 30 percent did not.
What role do T helper cells play in defense?
But antibodies don’t just fight infection. So-called T helper cells also play an important role, as they can remember for years which pathogens the body has successfully fought. However, testing on these immune cells is far more complex than antibody testing, as Gerard Krause of the Helmholtz Infection Research Center on Deutschlandfunk said.
In a small study, researchers at the Karolinska Institute in Stockholm tested the blood samples of 2,000 people in the Swedish capital for evidence of T-cell immunity to Sars-Cov-2. They found that some people did not have antibodies, but still had T-cell immunity – especially people who had very mild or rarely detectable symptoms. So the actual percentage of people who have already had a corona infection and are immune for the time being may be higher than antibody studies suggest. This has also recently been communicated in relevant studies.
What does this mean for vaccine development?
According to our research team, when an immune reaction is mentioned in vaccination studies, it refers to the production of antibodies. It is unclear how long immunity is achieved and how long it lasts. In addition, to date it is only clear to the vaccine candidate from Oxford University that the vaccine also produces suitable T memory cells – but that would be relevant for long-term immunity. The DLF Research News editorial team has collected information on the status of vaccine research here.
What are the benefits of plasma treatment with antibodies?
In the USA, the treatment of Covid 19 victims with plasma from patients who have already recovered has now been granted an emergency license. The blood plasma contains antibodies that are supposed to help the sick – a process that has been practiced for over a century. To date there have been indications for Covid-19 that critically ill patients survive somewhat more frequently when plasma is given antibodies than without. The results are unclear, because patients usually received other drugs in addition to the plasma. Therefore, official approval for the treatment is still pending in the USA. Critics accuse US President Trump of having initiated the emergency approval largely because of the presidential election campaign.
DLF science correspondent Volkart Wildermuth has collected more information on immunity to this new coronavirus.
Further articles on the coronavirus
We’ve created a news blog. Given the large amount of information, this provides an overview of the most important current developments.
Numbers and dates
+ Current developments: Figures on the coronavirus in Germany (as of 19 November)
+ Situation in Germany: What does the rapid rise in new infections and the value of incidence mean? (Status: 10/22)
Test and defense
+ Tests for coronavirus: when, where and how? (Status: October 29th)
+ How useful are mass tests for the whole population? (On November 15)
+ Corona infection: how reliable are the tests? (Status: November 18)
+ Treatment: This is how far the vaccine against the coronavirus research is (on 16 November)
+ Remdesivir and Co: how far is the drug search against Covid-19? (From October 16)
+ Infection: What do we know so far about redefinition and immunity against the coronavirus? (Status: 10.10.)
+ Hospitals: What the increase in corona infections means for them (on November 14th)
Contagion and Transmission
* Transmission: how contagious are children? (On November 17)
+ Transmission: What role do aerosols play (from 10.10.)
+ Face masks: What to know about protective masks (on October 29th)
+ Excess mortality: how deadly is the coronavirus really? (On November 14th)
+ Travel alert: Current list of risk areas (on November 13th)
You can also find the Dlf news on Twitter at: @DLFNews.