Why 'waning immunity' from COVID-19 vaccines isn't as bad as it sounds

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Canadians concerned over waning immunity from COVID-19 vaccines, breakthrough infections and the need for booster shots in the general public could benefit from a dose of some important context, experts say.

Antibodies, your first line of defence against COVID-19 infection, do decline — and may even be doing so as you're reading this — but that's not unexpected.

While one aspect of your vaccine-induced immunity to COVID-19 is technically "waning" in the weeks and months after vaccination, that's not necessarily a bad thing — because it's not your immune system's only form of protection against the virus.

"I don't even like the term," said University of Toronto immunologist Jennifer Gommerman. "And the reason I don't like the term is that it implies that the immune response in its entirety is declining."

It's "entirely normal" for antibody levels to drop initially after vaccination and your immune response to the virus to become "contracted" over time, she said. But your body is also creating "highly efficient" memory B cells to fight off COVID-19 long term.

B cells work quickly to generate large quantities of antibodies in the weeks after vaccination, but they typically produce more effective antibodies as time goes on, helping sharpen the long-term response to a virus.

So while reports of waning immunity may sound concerning, that initial decrease in antibody levels may also be necessary in the fight against COVID-19, as it helps fine-tune the immune system's plan of attack.

A new study published in the journal Science found "robust cellular immune memory" from B cells for at least six months after mRNA vaccination against all circulating strains of the virus — even the highly contagious delta variant.

The researchers found those memory cells, unlike the initial wave of antibodies, continue to learn how to fend off the virus months after vaccination and are actually getting better at it over time.

"That doesn't sound like 'waning' to me," Gommerman said. "There's a natural contraction, but waning implies that something bad is happening." 

Reports of waning immunity and breakthrough infections have sporadically emerged across Canada in places like the Northwest Territories and New Brunswick, but lack important context and data on who is seriously affected and why.

The N.W.T. has been in the midst of a COVID-19 outbreak since mid-August that started in the Sahtu region before spreading to Yellowknife and its surrounding communities. It has infected 1,584 residents.

During that time, there have been 54 hospitalizations attributed to the outbreak, about 17 of which were among fully vaccinated people. A government spokesperson declined to comment on how many of the nine deaths in the territory were among those fully vaccinated.