Are people immune after a corona infection? Reports of re-infection and dwindling antibodies had fueled doubts. But recent studies show that immunity could last a long time – maybe even years. This is of great importance for the use of vaccines.
It has long been one of the big questions about the coronavirus: How long does immunity against the pathogen last after an illness is over? This is also important in view of the recent success reports on the effectiveness of corona vaccines. Because a high level of protection is one thing – how long it lasts is another. But new studies on long-term immunity give hope.
Reports from the past few months had repeatedly raised the possibility that immunity to Sars-CoV-2 could only exist for a short time. For example, individual cases were repeatedly discovered in which people had contracted the coronavirus a second time. At the same time, there were observations that many infected people do not form any antibodies against the pathogen.
One also caused a stir Study from Great Britain taken care of, after which the amount of antibodies against Sars-CoV-2 in the blood in the months after the infection drops sharply in some cases. A study by the Chinese University of Chongqing had also shown that antibodies can dwindle considerably within two to three months. However, experts subsequently emphasized that a falling antibody level after an infection is normal and initially does not say anything about immunity – what is more important is the memory of the immune system.
Immune cells after eight months
A team from the La Jolla Institute for Immunology in California and other researchers have now found new evidence that immune memory could work quite well in the case of Sars-CoV-2. When examining 185 people recovering from Covid-19, they discovered that the vast majority still had enough immune cells to fight off the coronavirus eight months later. “This level of memory will likely protect the vast majority of people from becoming seriously ill for many years,” Shane Crotty, one of the study’s lead authors, told the New York Times. The study has so far only been published on a preprint server and has not yet been checked by other researchers.
Another, earlier one study from the USA supports the hope of stable immunity. Researchers led by immunologist Marion Pepper from the University of Washington had examined how strong the immune memory is in infected people who show only mild symptoms. In addition to the amount of antibodies, they also analyzed other components of the immune system – such as B and T memory cells. The result: The memory cells not only remained after the infection, but in some cases even increased in the months after the infection, the authors write.
Another one appeared in the summer study, which provided other evidence of permanent immunity: In the blood of people who had Sars 17 years ago, researchers still found T memory cells against the now-disappeared pathogen Sars-CoV, which is closely related to Sars-CoV-2 . Another investigation also found the very efficient cytotoxic T cells or T killer cells in Covid-19 convalescents who no longer had any antibodies – they can destroy cells in the body that are infected by viruses.
Experts see the studies as evidence that the human immune system does not react any differently to Sars-CoV-2 than to other pathogens. The immunologist Akiko Iwasaki told the “New York Times” that she was not surprised that the body was building up a permanent immune defense against Sars-CoV-2, because “that is what should happen”. Nevertheless, it is “exciting news“.
The findings also give rise to hope that highly effective vaccines such as those from Biontech / Pfizer or Moderna could actually have an impact on the pandemic. Because vaccines train the body’s own defense system even better than a natural infection, say experts. This means that they usually offer longer-lasting protection against re-infection. Here, too, T and B memory cells play a key role against Sars-CoV-2. “While the natural infection can lead to a poor immune memory that may not last, the vaccine will give you a strong permanent memory,” said immunologist Danny Altmann of Imperial College London. If all of this also applies to Sars-CoV-2, then permanent immunity through vaccinations would be tangible – and thus possibly an end to the pandemic.