Fears that our immune system may quickly forget its encounter with the SARS-CoV-2 virus are increasingly unfounded with an Australian study revealing that our blood is still able to produce a strong response eight months after infection. .
This is good news for those concerned that COVID-19 vaccines will not provide the period of protection needed to control the spread of the virus to the entire population.
“This has been a black cloud about the potential protection that any COVID-19 vaccine could provide and gives real hope that once a vaccine or vaccines are developed, they will provide long-term protection,” says Menno, a University immunologist. of Monash. van Zelm.
While it is still too early to know how long immunity to this specific coronavirus can last, we can be sure that time will probably be on our side.
In a collaboration between Monash University, Alfred Hospital and Melbourne’s Burnet Institute, the researchers analyzed blood samples taken from 25 volunteers diagnosed with COVID-19.
Each sample provided a snapshot of the state of the immune system, from just four days after infection to eight months.
Another 36 individuals with no history of the disease also provided one or two blood samples for comparison.
Positive samples in COVID suggest that floating SARS-CoV-2 antibody concentrations begin to disappear only 20 days after symptoms appear, a finding that matches previous studies suggesting that antibody levels drop rapidly, especially in mild cases of COVID-19. .
While this is not surprising in itself, it has caused consternation among immunologists as to whether we should expect waves of reinfection in the coming years.
Antibodies are like shots for the immune system, allowing you to easily pounce on past criminals who dare to show your face again. Without them, it is all too easy for a past infection to re-enter.
In the case of some pathogens, these “desired” chemical posters are maintained for years. Measles, for example, causes an antibody response that barely falls throughout your life.
Other agents of the disease fade from memory a little faster. For tetanus, this act of extinction takes just over a decade, and requires frequent reminders in the form of booster shots to push the system to reprint a batch of antibody ‘cup shots’.
The key to this antibody printing service is white blood cells called memory B cells. Formed during an infection by printing specific antibodies of an invader, these cells can hide for decades once the heat fades, ready to generate a new supply of antibodies at a previous time if the pathogen reappears. .
To see if an immune system known as COVID still had enough B cells to do the job after a few months, the researchers introduced fluorescently labeled SARS-CoV-2 pieces into the infected blood samples.
The analysis not only revealed a significant response in each of the COVID-19 blood samples, but also allowed the team to determine what types of B memory cells reacted to which particular piece of the virus’s body.
“These results are important because they definitely show that patients infected with the COVID-19 virus actually retain immunity to the virus and the disease,” says van Zelm.
And since the proteins analyzed by the study are considered primary target sites, we can expect most vaccines to also transmit a good level of immunity for at least eight months.
Beyond that? Time will tell. We hope that we can bring news in the coming years of continued immunity that will last far beyond expectations.
For the pandemic to be well controlled, if it is not eradicated completely, we will need at least 70% of the population to be immune in the same period of time. Only then can we be sure that the virus will have so few places to hide, that it may disappear.
Right now we can be pretty sure the window is eight months wide. Hopefully that’s enough.
This research was published in Scientific immunology.