How long do the Covid-19 vaccines work?

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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Pharmaceutical companies announce promising results on their corona vaccines. But how long does the protective effect last?

The headlines are optimistic: The corona vaccine candidates from Moderna and Biontech / Pfizer are said to offer 90 percent or more protection against illness, and a vaccine from the British-Swedish pharmaceutical company AstraZeneca reports at least 70 percent effectiveness.

All hopes are now directed towards the fact that the vaccines will help stop the spread of the pathogen in the foreseeable future and contain the pandemic. But how long does the body have at least some protection against the viruses?

Long-term results are still missing

No long-term studies can yet be available that provide the corresponding answers - the study duration has so far been a few months in each case. A recently published study by the La Jolla Institute of Immunology in California looked at infected people.

According to this, both antibodies and T cells - two of the central weapons of our immune system - are still detectable at least five months after the onset of symptoms. This also applies to courses with mild symptoms. The study was published as a so-called preprint, so it has not yet been reviewed by independent experts.

Sterile immunity prevents the virus from passing on

For Thomas Jacobs from the Bernhard Nocht Institute for Tropical Medicine in Hamburg, these observations are encouraging in view of the multi-armed reaction of our immune system. He points out two points: In this study there is what is known as sterile immunity. Not only does it protect the vaccinated person, it also prevents them from passing the virus on to others. This is crucial for herd immunity.

Sterile immunity depends on the presence of high levels of neutralizing antibodies. In this case, a virus is caught before it can penetrate cells, explains Jacobs. Corresponding vaccines would probably produce an even better antibody response than a natural infection. As long as there are enough antibodies, one can assume robust, if not sterile immunity, said Jacobs.

T cells detectable for a long time

In addition, the T-cell response was also detectable for several months. This means that the symptoms of Covid 19 disease can be expected to decrease, says Jacobs. Such clinical immunity would ensure that sick people would only get cold symptoms, for example, as with more harmless coronaviruses.

A sterile, lifelong protective effect through the vaccines cannot currently be assumed. Nonetheless, the results of the preprint study would provide a welcome framework for the expected immunity from the vaccine.

Many T cells prevent severe disease

Another study group recently reported that the T cells are still detectable six months after a Sars-CoV-2 infection. "This is very promising news: if natural infection with the virus can produce a robust T-cell response, it may mean that a vaccine could do the same," said Fiona Watt, executive chairman of the UK Medical Research Council, in an article of the specialist journal "The British Medical Journal".

Vaccinations can protect you longer than through illnesses

Carsten Watzl, immunologist at the Leibniz Institute for Labor Research at the Technical University of Dortmund, points out that with other coronaviruses that cause normal colds, one to one and a half years are protected against renewed infection on average. A natural infection is not comparable to a vaccination, however, the immune response is more efficient after a vaccination, says Watzl, who is also Secretary General of the German Society for Immunology. "So the hope is that the vaccine candidates will keep the immunity much longer."

Whether antibodies or T cells or a mixture of both are important for immunity cannot yet be answered, says Watzl. Immunologist Jacobs adds: "A sterile immunity is presumably mainly dependent on a high number of neutralizing antibodies, while the severity of the course is related to the T-cell response, so that there is probably no" important "one in this context."

Regular refreshment only necessary for medical staff?

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 carers 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 be more than enough."

In addition, it is currently still uncertain whether a vaccination will also protect against passing on the pathogen. "If the antibody response is high, the likelihood of this is very low," explains Jacobs. With clinical immunity, however, there could still be a risk of spreading - further studies would have to follow here.

At some point just one pathogen among many

Overall, according to immunologist Watzl, the vaccines would initially calm the situation. "Even if the protection only lasts two years, it could still be vaccinated," he says. "That would be annoying, but manageable." And Sars-CoV-2 would become another pathogen against which you have to be vaccinated regularly. "But then we would no longer have a pandemic." (Cf / dpa)

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