Fears that our immune system could quickly forget its encounter with 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 who are concerned that COVID-19 vaccines do not provide the protection period needed to control the spread of the virus throughout the population.
“This has been a black cloud that hangs over the potential protection that can be provided by any COVID-19 vaccine and gives real hope that once a vaccine or vaccines are developed, they will provide long-term protection,” says Monash University. immunologist Menno van Zelm.
Although it is still too early to say how long the immunity to this specific coronavirus may last, we can be sure that time will probably be on our side.
In a collaboration between Monash University, Alfred Hospital and the Burnet Institute in Melbourne, researchers analyzed blood samples taken from 25 volunteers diagnosed with COVID-19.
Each sample provided a snapshot of the status of the immune system from just four days after infection to as long as eight months.
Another 36 people with no medical history also provided one or two blood samples for comparison.
The COVID-positive samples suggest that concentrations of free-flowing SARS-CoV-2 antibodies begin to fade only 20 days after the onset of symptoms, a finding that is in line with previous studies suggesting that antibody levels fall rapidly, especially in mild cases of COVID-19.
While this is not in itself surprising, it has caused concern among immunologists over whether we could expect waves of reinfections in the coming years.
Antibodies are like mugs for the immune system, so it can easily skip past offenders who dare to show their face again. Without them, it is all too easy for a previous infection to roll right away.
In the case of some pathogens, these chemical hold ‘desired’ posters for years. Measles, for example, elicits an antibody response that is unlikely to decrease throughout your life.
Other pathogens disappear from memory a little faster. For tetanus, this disappearing action takes a little over a decade and requires frequent reminders in the form of booster vaccines to push the system to print a new batch of antibody ‘mug shots’ again.
The key to this antibody printing service is white blood cells called memory B cells. Formed during an infection to print antibodies specific for an invader, these cells can hide away for decades when the heat dies down, ready to generate a fresh supply of antibodies at a moment’s notice should the pathogen reappear .
To see if a COVID-known immune system still had enough B cells to do the job after just a few months, the researchers introduced fluorescently labeled pieces of SARS-CoV-2 to the once infected blood samples.
The analysis not only revealed a significant response in each of the COVID-19 blood samples, but allowed the team to determine which types of B memory cells responded to which particular part of the body of the virus.
“These results are important because they ultimately show that patients infected with the COVID-19 virus actually maintain immunity to the virus and the disease,” says van Zelm.
And since the proteins analyzed by the study are considered the primary sites to target, we can expect that most vaccines will also provide a good level of immunity for at least eight months.
Besides the? Time will tell. Hopefully we can bring news in the coming years with continued immunity that lasts far beyond expectation.
In order for the pandemic to be well brought under control if it is not completely eradicated, we need at least 70 percent of a population to be immune within the same time window. Only then can we be sure that the virus has so few places to hide that it may disappear.
Right now, we can be pretty sure the window is eight months wide. Let’s hope that’s enough.
This research was published in Scientific immunology.