The development of vaccines against the coronavirus is making rapid progress. But how long does immunity last? And how great is the risk of reinfection?
No long-term studies are yet available that provide the corresponding answers – the study duration has so far been a few months. According to a British study, immunity after a corona infection is very likely to last for at least six months. This was announced by study director David Eyre from Oxford University. No new symptomatic infections were found in any study participant who tested positive for antibodies. For the study, UK health workers were examined from April to November 2020.
Another recently published study by the La Jolla Institute of Immunology in California even suggests that immunity could last for many years. As the New York Times reports, the research is in line with another recent finding: survivors of the 2002 Sars epidemic, caused by another coronavirus, still carried certain vital immune cells 17 years after their recovery.
Antibodies and T cells are crucial
Thomas Jacobs from the Bernhard Nocht Institute for Tropical Medicine in Hamburg points out two points that are crucial for longer or even permanent immunity: If the body has many neutralizing antibodies, a virus is intercepted before it can penetrate cells. Corresponding vaccines would probably produce an even better antibody response than a natural infection.
In addition, the T-cell response was detectable over several months in several studies. This leads to the expectation that the symptoms of Covid 19 disease will decrease, says Jacobs. Such clinical immunity would ensure that sick people would only get cold symptoms, for example, as with more harmless coronaviruses. Fiona Watt from the British Medical Research Council recently made a similar statement in an article in the specialist journal “The BMJ”.
No antibodies despite infection
The answer to natural immune protection is made more difficult by the fact that in some people who have been proven to be infected, no antibodies at all are found, as a study by the Jena University Hospital shows. In the former corona quarantine location Neustadt am Rennsteig, no antibodies against the pathogen could be detected in around half of the infected. A study by the Lübeck health department had also come to the conclusion that only 70 percent of those infected had developed antibodies, while 30 percent did not.
Researchers at the Karolinska Institute in Stockholm, on the other hand, tested the blood samples of 2,000 people in the Swedish capital for evidence of T-cell immunity to Sars-Cov-2 in a study. They were able to show that although some people did not have antibodies, they still had T-cell immunity – especially people who had only very mild or hardly detectable symptoms. The actual percentage of people who have already had a corona infection and are probably immune for the time being could therefore be higher than antibody studies suggest. This was also recently communicated in relevant studies.
Vaccination protection essential for certain groups
Whether antibodies or T cells or a mixture of both are important for immunity cannot yet be answered, says immunologist Carsten Watzl from the Leibniz Institute for Labor Research at the Technical University of Dortmund. With a view to vulnerable risk groups, for example in old people’s homes, it is more important to have a vaccine that offers sterile vaccination protection for nurses and other people who work intensively with risk groups, says Jacobs. These would then probably have to be vaccinated more often. For the general population, clinical immunity would therefore be sufficient.
What are the benefits of plasma treatment with antibodies?
In the USA, the treatment of Covid-19 sufferers with plasma from recovered patients was permitted by means of an emergency permit in August. The blood plasma contains antibodies that are supposed to help the sick – a procedure that has been practiced for over a century. So far there have been indications with regard to Covid-19 that seriously ill patients survive somewhat more often when plasma with antibodies is administered than without. The results are not clear, because the patients usually received other drugs in addition to the plasma. Researchers in this country also started a similar therapy study with the blood plasma of those who have recovered.
How does a reinfection work?
Most recently, there were several reports about individuals who were infected with the new corona virus for the second time within a short period of time. Researchers then speak of a mutation. So far, there are no research results on the course of a reinfection, as only a few cases of reinfection have been reliably documented. As early as spring, some cases became known in which the coronavirus could be detected again a few weeks later after a negative test. In these cases, researchers assume different scenarios: the virus could have stayed in the body and the disease flared up again later – or the tests were misleading because dead viral material could have been detected.
A 25-year-old American first tested positive for Sars-CoV-2 in mid-April after milder cold symptoms and diarrhea. At the end of May he was tested positive again – this time with fever, headache and cough, and he also had to be ventilated from time to time. The case was published in the journal “The Lancet Infectios Diseases” in mid-October. Further cases of reinfection are known from the Netherlands, Belgium, Ecuador and Hong Kong.
Further 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: Figures on the coronavirus in Germany (as of December 15)
+ High numbers of corona infections: is the incidence value 50 correct? (As of December 11th)
Test and protection
+ Protection: This is how the vaccination against the coronavirus should be organized (as of December 9th)
+ How useful are mass tests for the whole population? (Status: November 28th)
+ What good are night curfews (as of December 5th)
+ Corona infection: how reliable are the tests? (Status: November 18)
+ Treatment: This is how far vaccine research against the coronavirus is (as of December 14th)
+ Sick people: New findings in the search for drugs (as of December 16)
+ Infection: What is known so far about reinfections and immunity against the coronavirus? (As of November 30th)
+ What is the situation like in the hospitals? (As of December 14th)
Contagion and Transmission
+ Positive examples: Can Germany learn from other countries? (As of 3.12.)
+ Transmission: how contagious are children? (As of November 17)
+ Transfer: What role do aerosols play (as of 10.10.)
+ Excess mortality: How deadly is the coronavirus really? (As of December 10th)
+ Travel warning: The current list of risk areas (as of December 14th)
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