The latest research shows immunity to COVID-19 lasts for at least 8 months

Fears that our immune system could quickly forget the encounter with the SARS-CoV-2 virus are increasingly unfounded by Australian research that reveals that our blood is still able to achieve a strong response eight months after infection.

This is good news for those concerned that vaccines against COVID-19 will not provide the period of protection needed to manage the spread of the virus throughout the population.

“This is a black cloud that hangs over the potential protection that any COVID-19 vaccine could provide and gives real hope that, once a vaccine or vaccine is developed, it will provide long-term protection,” said Monash University immunologist Menno van Zelm.

Although it is too early to say 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 the Burnet Institute in Melbourne, 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 as much as eight months.

Another 36 people without a history of the disease also gave one or two blood samples for comparison.

COVID-positive samples suggest that free-floating antibody concentrations to SARS-CoV-2 begin to disappear only 20 days after the onset of symptoms, consistent with previous studies suggesting that antibody levels decline rapidly, especially in milder cases of COVID-19.

While this is not surprising in itself, it has caused astonishment among immunologists as to whether we should expect waves of re-infection in the coming years.

Antibodies are like cracking the immune system, allowing it to easily pounce on past perpetrators who dare to show their face again. Without them, it is too easy for the past infection to return to the waltz.

In the case of some pathogens, these chemical posters are sought after for years. For example, measles elicits an antibody response that barely drops during your lifetime.

Other disease agents disappear from memory a little faster. For tetanus, this act of disappearance lasts a little more than a decade, which requires frequent reminders in the form of auxiliary vaccines in order to push the system to print a fresh number of “cups” of antibodies again.

The key to this antibody printing service is white blood cells called memory B cells. Created during an infection to print attacker-specific antibodies, these cells can hide for decades after the heat subsides, ready to create a fresh supply of antibodies at the moment the pathogen should reappear.

To determine if the immune system familiar with COVID still has enough B cells to do the job after just a few months, researchers introduced pieces of SARS-CoV-2 fluorescently labeled into infected blood samples for some time.

The analysis not only revealed a significant response in each of the COVID-19 blood samples, but also enabled the team to determine which types of B memory cells respond to which particular part of the virus body.

“These results are important because they definitely show that patients infected with the COVID-19 virus actually retain immunity against the virus and the disease,” says van Zelm.

And since the proteins analyzed in the study are considered the main target sites, we can expect that most vaccines will also provide a good level of immunity for at least eight months.

Behind that? Time will tell. We hope to bring news in the coming years of continued immunity that lasts well above expectations.

For a pandemic to be well controlled, if not eradicated at all, we will need at least 70 percent of the population to be immune within the same time frame. Only then can we be sure that the virus will have so little room to hide, that it could simply disappear.

At the moment we can be pretty sure the window is eight months wide. Let’s hope that’s enough.

This research was published in Scientific immunology.