Why Our Immune System Might Be Better Than We Think At Fighting COVID-19 | CBC News (2023)

This is an excerpt from Second Opinion, a weekly roundup of health and medical science news emailed to subscribers every Saturday morning. If you have not yet registered, you can do so atby clicking here.

There is currently a lot of confusion and speculation about immunity to COVID-19.

You may have seen the headlines this week suggesting that the antibodies the immune system makes to fight the coronavirus are rapidly declining after infection, threatening hopes of long-term immunity to the virus.

But the problem is more complicated than it seems and more hopeful.

The Prepress Studio, which has not been peer-reviewed, found that the number of people with detectable antibodies in their blood in England has fallen from 6 per cent of the population at the end of June to just 4.4 per cent in mid-September.

The researchers concluded that there was "decreased immunity in the population" and an "increased risk of reinfection" and that the collaborative study of 365,000 patients clearly showed that detectable antibodies decreased.

But while the study and its dire conclusions made headlines around the world, experts say there is much more to consider before we can definitively say coronavirus antibodies don't last long enough to protect us.

After infection, a drop in antibodies is to be expected

An important factor to note is that it's not uncommon for immunity to wane after infection, said Alyson Kelvin, an assistant professor at Dalhousie University and a virologist at the Canada Center for Vaccination who evaluates Canadian vaccines forVIDO-InterVac-Labornot Saskatoon.

"Just showing that antibodies decrease after an infection doesn't simply mean that we are no longer protected," he said. "Our immune system is more complicated than what is good."

In fact, a drop in detectable antibodies is expected after an infection, and that high levels of antibodies remaining after a disease has passed could actually be a bad thing, Kelvin said.

"Normally we would associate a high level of activated immune response with more than one autoimmune disease in the absence of a threat," he said.

"So what we want to see is that some of knowing that our bodies are in control goes away after we've eliminated the virus."

The other important factor is that the immune system can actually remember how to make new antibodies when needed to fight future infections by storing types of protective white blood cells in the body called B cells.

Kelvin said just because there are no detectable antibodies in the blood doesn't mean we don't have reserves of these immune memory cells stored elsewhere in our body, such as in our bone marrow.

"Typically, memory B cells are hiding there, waiting for further exposure," Kelvin said. "Because these antibodies don't circulate when you're not exposed, you need to store them for when you need them."

Conflicting studies create confusion

another study,published this week in the journal Scienceand peer review, confusion over immunity to coronavirus may have increased.

He studied antibody responses in plasma samples from more than 30,000 COVID-19 patients at Mount Sinai Health System in New York City between March and October.

It came to a very different conclusion from the previous study: that more than 90 percent of patients produced moderate to high levels of antibodies, strong enough to neutralize the virus and lasting for many months after infection.

CLOCK | Antibodies to COVID-19 can wear off quickly, the study says:

One difference between the two studies is that the preprint studied patients ranging from asymptomatic to severe, while the published study focused on inpatients, who were mainly symptomatic.

"There seems to be a kind of split that milder cases don't have this noticeable increase in antibody responses for long periods of time after infection," Kelvin said. "That might be more obvious in people with a more severe infection."

The researchers in the New York study concluded that the antibodies they found were likely produced by "long-lived plasma cells in the bone marrow," supporting the notion that latent immune-memory B cells may be hiding there.

"This study suggests that most people infected with SARS-CoV-2 [the coronavirus that causes COVID-19] produce protective antibodies that are likely to protect against reinfection," Kelvin said.

"This would support the idea that we will be able to produce a vaccine that is safe and results in a protective immune response."

How our immune system reacts to the coronavirus

After exposure to a virus, either through an infection or a vaccine, the body goes through what's called an "expansion phase," during which these memory immune cells produce antibodies in response, something Kelvin likens to climbing a mountain.

Once the body thinks it's cleared the infection and reached the top of the mountain, these antibodies begin to wane during what's known as the "contraction phase," the beginning of the descent down the mountain.

When you reach the bottom of the mountain, the body goes into a "memory phase" where the most potent antibodies are stored until the next exposure, e.g. B. the experience of maybe climbing the mountain better next time.

It is believed that the B cells are not detectable in the bloodstream at this point, but are entering immune reservoirs in the body such as the bone marrow, meaning researchers could miss them if they only focus on the blood

"We don't yet know what amount of these antibodies is actually needed to prevent infection," said Dr. Lynora Saxinger, an infectious disease specialist and associate professor of microbiology and immunology at the University of Alberta.

"But there are many examples of low antibody levels that rise rapidly upon re-exposure to an infectious agent because memory B cells release antibodies upon re-exposure."

Another tool our body uses to fight infection are T-cells, another type of white blood cell stored in the body that can also attack the virus the next time it encounters it, but are adetached arm of the immune system.

A recent article published in Cell magazinediscovered that a balance of T-cells and B-cells produced in the body could lead to a better outcome after coronavirus infection, and Kelvin said a better understanding of T-cell immunity could help vaccine development .

On a positive note, memory B cells, which can protect against future infection, have already been demonstrated in both symptomatic and asymptomatic COVID-19 patients, as mentioned inanother study published in the journal Naturethis week.

Kelvin said that COVID-19 patients who develop serious illness or die after being infected with the virus may have a reduced ability to produce antibodies because they maytargeting and destroying these B cells.

"These results would support the idea that 'herd immunity' through natural infection does not lead to long-lasting immunity," he said. "Which, in turn, puts our vulnerable populations at risk of death."

Other coronaviruses such as SARS and MERS could also provide clues as to how long dormant antibodies are waiting to protect us from infections in the future.

"In both SARS and MERS, years after antibodies were undetectable, immune memory cells primed for specific responses to both viruses could still be found in recovered patients," said Dr. David Naylor, Co-Chairman of the US Federal Government Health.Immunity Working Group.

"Conclusion: Due to the millions of infected people, the duration of the epidemic and the still very low proportion of reinfections, it seems very likely that there will be a fairly long-lasting immunity to SARS-CoV-2 after an initial infection. "

Vaccines are the surest way to achieve immunity

It's important to note that research showing a decline in antibodies over time doesn't necessarily mean we're less likely to be able to develop safe and effective vaccines in the months to come.

"There is still a lot to learn about the durability of immunity," Naylor said.

No one expects any of the vaccine candidates to offer "unlimited immunity," and they may seem more like an annual flu shot, he said.

"The immediate question is whether the vaccines will achieve and maintain sufficient general immunity to keep the spread in check for us to get on with our lives."

Separately, Kelvin says immunity gained from vaccines is safer than that from rampant infections, a concept also known as herd immunity.

"More work is needed to understand how long immunity lasts," he said, adding that while a vaccine may also not provide long-lasting protection, it does not carry the same risk of death that COVID-19 patients face are.

"So a safe and effective vaccine would be the best way to control outbreaks."

To read Second Opinion's full newsletter every Saturday morning, subscribeby clicking here.