A new study suggests that most people who survive SARS-CoV-2 infection retain the protective memory they need to prevent a major relapse. The protection afforded by a vaccine can be long lasting.
- New research has found that people who have been exposed to COVID-19 may develop immunity to SARS-CoV-2 for 8 months or more.
- This is due to a long-lasting immune memory that allows the immune system to become active against the virus.
- However, due to differences in individual immunosuppressants, not everyone who has been exposed to COVID-19 will have long-term immunity against the virus.
Researchers at the La Jolla Institute in La Jolla, CA, looked at the four branches of the “adaptive” immune system – which protects against certain diseases – in people who have survived COVID-19, the disease caused by the SARS-CoV-2 virus. .
Between 5 and 8 months after the onset of their symptoms, about 95% of these immune system retained memory for the disease in at least three of its branches.
“Our data suggests that the immune response is there – and it remains,” said Dr. Alessandro Sette, who co-directed the study with Professor Shane Crotty.
The scientists measured levels of antibodies, B memory cells, and two types of T cells, all targeting the virus.
“To the best of our knowledge, this is the largest ever study for any infectious disease that has measured these four components of immune memory,” said Dr. Crotty.
The research appears in the journal Science.
Medical News Today has reported several smaller studies with apparent results in terms of post-infection immunity.
For example, researchers at the University of Arizona College of Medicine in Tucson found that people with COVID-19 infection were still exposed to anti-virus antibodies 5–7 months later.
In contrast, a study by Imperial College London in the United Kingdom suggested that antibody responses to the virus within population decline would follow the first wave of disease.
As a result, there have been concerns that the immune response of many people may be too weak to protect them from relapse. This would also affect the length of protection from vaccines.
“Of course, the immune response decreases to some degree over time, but that’s normal,” says Dr. Sette. “That’s what immune responses do. They have the first stage of ramping up, and after that miraculous extension, eventually the immune response partially contracts and gets to a stable level. ”
Prof. did. Sette and his colleagues analyzed 254 blood samples from 188 individuals who underwent COVID-19. Of these, 43 samples were taken at least 6 months after infection.
They found that levels of antibodies targeting the spike protein, which the virus uses to enter its host cells, remained relatively stable for at least 6 months.
More striking, perhaps, were the B memory cells that secrete these antibodies more abundant 6 months after incidence of symptoms than at 1 month.
It is likely that these cells would make up the production of antibodies after the second exposure to the virus.
The researchers also measured levels of T helper cells, which employ other parts of the immune system to fight infection, and kill T cells, which destroy infectious cells.
They found that, 3-5 months after the onset of symptoms, the number of these two T cell types targeting the virus had significantly decreased.
The scientists believe that it is a good indication that some antibodies, B memory cells, and T cells remain in pesron blood more than 8 months after infection because the different branches of the immune system working together.
“This means that there is a good chance that people will have an immune system, at least against serious disease, for that period of time, and possibly for much longer,” said Dr. Crotty.
Similarly, the study found significant changes in the amount of immune memory between individuals. This suggests that people with relatively weak adaptive immunity to the virus may remain prone to relapse.
Authors’ Warning:
“We have seen heterogeneity in the magnitude of variable immune responses to SARS-CoV-2 leading to immune memory level. It is therefore possible that a fraction of the population with SARS-CoV-2 infection with low immune memory would tend to be redefined relatively quickly. “
They note that some reconfirmation cases have been confirmed. For example, a case was reported in Hong Kong and another in the United States.
The authors state that future studies should include longer-term data for each subject to gain a more detailed understanding of the stability of antibody protection against the virus.
In addition, they acknowledge that local protective memory in the upper respiratory tract may play an important role in determining the resilience of a person. The current study only measured immune cells and circulating antibodies in the bloodstream.
Finally, it is important to remember that the researchers did not design the study to address the possibility that mutations may allow the virus to “escape” the altered immune response after an initial infection or vaccine.
For live updates on the latest developments regarding the novel coronavirus and COVID-19, click here.