Immune after Covid-19: memory cells stay in the body for eight months

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In the middle of the preparations for global mass vaccinations at the end of this year and at the beginning of next year, happy news from the scientific community bursts into the dreary November mood. It gives hope for a much more positive Advent season than expected, because it gives the answer to some of the most pressing questions of the time: How long does immunity last after a Covid infection? Can we get the pandemic under control with the help of vaccinations and a growing number of those who have recovered?

According to current knowledge, immune cells could protect us for years after a Covid 19 infection. According to the latest data, eight months after infection, people still have many memory immune cells and killer cells that prevent re-infection. To the delight of researchers at the La Jolla Institute for Immunology in California, the analysis of data on 185 recovered people showed that various types of immune cells, including those that recognize the spike protein on the coronavirus, remain in the body for a very long time. The study was initially made available on a so-called preprint server, as the data had not yet passed through the scientific assessment process.

The result is therefore good news, as initial evaluations showed that the antibody level against the virus is falling rapidly. This fueled fears that people who had once suffered a corona infection could become infected again. In fact, quarantine requirements based on this preliminary assumption apply today. Boris Johnson, for example, the British Prime Minister who had Covid-19 a few weeks ago, had to be quarantined again. He came into contact with a person who tested positive. In Germany, the health department also sends people into quarantine if they have had close contact with an infected person, even if they have already been through Covid-19. Hopefully this will soon change after this study.

Duration of immunity is also a crucial issue for vaccinations

The latest data show that the important memory cells remain in the body despite no longer detectable antibodies. This should reassure experts around the world, because the duration of immunity is also a crucial question with regard to the medium and long-term effects of vaccination. There is still no long-term data on the potential vaccines. Biontech and Moderna only started their major studies in July. Curevac plans to start its phase 3 study this year and finish it by next March.

But it remains to be seen how often vaccinations have to be made. You have to get vaccinated against flu every year. With other vaccines, the effect lasts for many years, for example against polio or tetanus. It was already known that immunity to SARS (Severe Acute Respiratory Syndrome), a pandemic that raged mainly in Asia in 2002 and 2003, has lasted 17 years in those who have recovered.

Akiko Iwasaki, an immunologist at Yale University, told the New York Times that she wasn’t surprised that the body remembers an infection for a long time, “because that’s what it should do.” Still, she was relieved by the new results: “This is exciting news.”


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