New research released on Wednesday should offer comfort to covid-19 survivors who are worried about losing their natural immunity to the coronavirus soon. The findings suggest that in most people a robust immune response to the virus lasts at least eight months – and there are good signs that it may even take years.
There has been concern about declining immunity since almost the beginning of the pandemic. Related coronaviruses that cause the usual cold are known for their people often being infected and spread again reports of re-infections of covid-19 have emerged in 2020. Some studies have also suggested that the level of antibodies against the virus may drop significantly three months.
On the other hand, immunity is a complicated mess. Antibodies are not the only source of immunity to germs like the coronavirus. And, so far, confirmed versions of reinfection still seem rare. This new study, published in Science, seems to offer the latest look at how our immune responses to the virus change over time – and the verdict is largely positive.
Scientists studied the blood of 180 volunteers who confirmed covid-19, including samples taken six months after infection. The levels of antibodies against the virus dropped after infection but remained stable thereafter for up to eight months in most people. T cells specific for the virus also decreased slightly after three months, but then again at a steady level. Meanwhile, memory B cells, which help awaken the immune system in response to a known threat and create more antibodies when needed, were actually more abundant in the six-month point as on one month. This is especially encouraging because these B cells are crucial for longer-term immunity, the kind that lasts for years.
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The findings do not directly indicate that our immunity to covid-19 will absolutely last for eight months and longer. Scientists are still trying to figure out how these immune responses in the body can be translated into the real world. But everyone says: 95% of the people in the study have some immune memory in their antibodies, B cells, and T cells to the virus five to eight months after their symptoms first started. This indicates, the authors write, that ‘lasting immunity to secondary covid-19 disease is a possibility in most individuals.’
Antibodies are usually the most important part of the immunity to prevent re-infection by germs. This and other research have shown that our antibody levels against the coronavirus can vary considerably from person to person. This may explain why some people have been re-infected in such a short time, in some cases appear only three months later. But as experts have noted, the other aspects of our immunity should usually protect people from serious diseases if they are infected second time.
Although the current pandemic is still very bad, with daily cases, hospitalizations, and deaths in the US on record-high levels. Iit will take more time to figure out other important questions, such as how long immunity is provided by vaccine. But in a sea of bad news, there is at least hope to catch on.