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Headlines give cause for optimism: Moderna and Biontech / Pfizer’s corona vaccine candidates are said to offer 90% or more protection against disease, and a vaccine from British-Swedish pharmaceutical company AstraZeneca reports at least 70% efficacy . All hopes are now on the fact that vaccines will help stop the spread of the pathogen in the near future and contain the pandemic. But how long does the body have at least protection against viruses?
Long-term studies providing the corresponding answers are not yet available: the duration of the study has so far been a few months. A recent study from the La Jolla Institute of Immunology in California looked at infected people. According to this, both antibodies and T lymphocytes – two of the central weapons of our immune system – are still detectable for at least five months after the onset of symptoms, even if the symptoms are mild. The study was published as a so-called prepress, so it has not yet been reviewed by independent experts.
Mild course of the disease
For Thomas Jacobs of the Bernhard Nocht Institute for Tropical Medicine in Hamburg, these observations are encouraging given the multi-armed reaction of our immune system. He underlines two points: in this study there is what is known as sterile immunity, which depends on a large number of neutralizing antibodies. If the body has a lot of them, a virus is caught before it can enter cells. Matching vaccines would likely produce an even better antibody response than a natural infection. As long as there are enough antibodies, robust, if not sterile, immunity can be assumed, Jacobs said.
Furthermore, the T cell response was also detectable for several months. This leads to the expectation that the symptoms of Covid 19 disease will subside, Jacobs says. Such clinical immunity would ensure that sufferers only experience cold symptoms, for example, as with the more harmless coronaviruses.
More efficient immune response after vaccination
A sterile and permanent protective effect through vaccines cannot be assumed at the moment. However, the results of the preprint study would provide a positive picture for the immunity expected from the vaccine.
Another study group recently reported that T cells are still detectable six months after a CoV-2 SARS infection. “This is very promising news: if a natural infection with the virus can produce a robust T cell response, it could mean a vaccine could do the same,” said Fiona Watt, executive chair of the UK Medical Research Council, in an article in the specialized magazine “The BMJ”.
Carsten Watzl, an immunologist at the Leibniz Institute for Occupational Research at the Technical University of Dortmund, points out that with other coronaviruses that cause normal colds, one to one and a half years is protected on average from a new infection. A natural infection is not comparable to a vaccination, however, the immune response is more efficient after a vaccination, says Watzl, who is also the general secretary of the German Society of Immunology. “So the hope is that vaccine candidates will maintain immunity much longer.”
“Annoying, but manageable”
Whether antibodies or T cells or a mixture of both are important for immunity, it’s still not possible to answer, Watzl says. Adds immunologist Jacobs: “Sterile immunity presumably depends mainly on a large number of neutralizing antibodies, while the severity of the course is related to the T cell response, so there is probably no” important “one in this context.” .
From the perspective of vulnerable risk groups, such as in nursing homes for the elderly, it is more important to have a vaccine that offers sterile vaccine protection for nurses and other people who work intensively with risk groups, Jacobs says. These should therefore probably be vaccinated more often. “For the general population, clinical immunity would be more than enough.”
Furthermore, it is currently still uncertain whether a vaccination will also protect against the passage of the pathogen. “If the antibody response is high, the likelihood of this happening is very low,” Jacobs explains. With clinical immunity, however, there may still be a risk of spread – further studies should follow.
Overall, according to immunologist Watzl, the vaccines initially calmed the situation. “Even if the protection lasts only two years, you could still be vaccinated,” he says. “It would be annoying, but manageable.” And Sars-CoV-2 would become another pathogen that you need to be vaccinated against regularly. “But then we wouldn’t have a pandemic anymore.”
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