COVID-19 immunity: what we're learning and what we still need to figure out

When we look for our way out of this pandemic, every safe exit route involves the immune system. Either we'll fight off the virus, and generate immunity, or researchers will develop a vaccine that will provide immunity. 

But the more we learn about this coronavirus, the more perilous our road may be to get to these safe exit routes.

According to McMaster University immunologist Dawn Bowdish, research on how our immune system responds to other coronaviruses suggests that a vaccine or exposure to the virus may not provide the kind of lifelong immunity we get with the chickenpox vaccine. 

"What we expect based on what we've learned from other related viruses like SARS and MERS is that the immune response will likely fade," she told Quirks & Quarks' host Bob McDonald. 

The durability of immunity is critical to understand so we can know when it's safe for recovered individuals to go back to work, especially if they're on the front lines. It's also going to be essential for vaccine research so we can understand how long we might be protected. 

But there are paradoxes appearing as we understand more about how we respond to this coronavirus. For one thing Bowdish said the strength of immune response in patients who died from COVID-19 looks very similar to the response in those who lived.

"They had the same levels of antibodies, which are one feature that generally gets rid of a virus, but they also have one major difference in their immune response," she cautioned.

Immune cells going where they don't belong

Scientists studying autopsy samples from people who died from COVID-19 found that an important set of immune cells is active — but possibly in the wrong place.  These are T cells which are part of the adaptive immune system that can learn to recognize and attack viruses with great precision.  

"It looks — to all the world — that those cells are ending up in the lungs and helping clog the air exchange in the lungs," said Bowdish.

"If these T cells get inappropriately activated, they sort of lose their precision and so there is a lot of collateral damage. And that looks like it might be part of the problem in this infection," added Bowdish. 

What this may mean for vaccine development

For years, the focus of most vaccine development was to elicit antibodies that could neutralize viral pathogens by binding to them and preventing them from infecting our cells.  

That strategy has worked with many viruses. Tetanus might be a good example as Bowdish expects that vaccine may provide the same type of immunity that we may see with the COVID-coronavirus. 

With the Tetanus vaccine, "the antibodies do exactly what they're supposed to do — they bind, they stop the toxin from making us sick."

But at the moment, we still don't know enough about the specific antibody response to the COVID-19 virus to know how well they stick to the virus to prevent them from entering our cells, nor how well they do their job of clearing the virus.

The worry for Bowdish when it comes to our ability to develop a vaccine is that we're dealing with another virus like HIV.

"We actually make tons of antibodies to the HIV virus if we're infected, but none of those cells stick in a way that they stop the virus from infecting," she said about HIV's antibody response, which she called "completely useless."

She's hoping she and other scientists can find a "magic bullet" antibody that will prevent the virus from infecting our cells.

Written and produced by Sonya Buyting