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Boosters are required because of waning vaccine immunity. The Omicron variant is a threat because of its apparent ability to evade existing immunity. Achieving herd immunity is essential (or impossible).

Those kinds of statements are commonplace in daily media coverage, and even kitchen table conversations.

After almost two years of the COVID-19 pandemic, “immunity” remains the word of the moment.

Immunity, both individual and collective (the herd), is also essential if we hope to shift COVID-19 from being a devastating pandemic illness to a manageable endemic one.

But we still have a lot to learn about the body’s immune response to SARS-CoV-2, the virus that causes COVID-19.

We know that the vaccines we have provide pretty good protection against infection with the coronavirus.

We know too that people who have been infected with the virus develop antibodies that confer some immunity.

But is acquired immunity better than vaccine-induced immunity?

That’s the subject of much debate. The answer seems to be, like many immunity-related questions, “it depends.”

Research shows that the best immune protection comes from a combination of being infected and getting vaccinated. That means that even those infected should get their shots.

We can’t forget that contracting COVID-19 comes with risks, from severe illness to long-COVID, so this isn’t an endorsement for getting infected deliberately.

On the surface, immunity is a pretty simple concept. When you are exposed to a pathogen such as coronavirus, the immune system fights off the intruder with killer T-cells and B cells; it also produces antibodies that “remember” the germ and react quickly if it arises again. (Vaccination essentially tricks the body into thinking there is a viral attack so that it produces antibodies without having to suffer illness.)

But immune response is actually a complex process with a lot of moving parts.

And the state of immunity in the world is also a complicated puzzle.

We started off with everyone susceptible to the novel coronavirus and, two years later, there is a patchwork of immunity created by infections (at least 270 million worldwide) with different variants, and vaccination with a variety of products (4.2 billion people have received at least one dose, and 365 million three doses).

Susceptibility to infection varies wildly, and so does immune protection.

There are three key areas that scientists are studying closely: the strength of immunity, the durability and whether variants can sidestep antibodies.

A person can be exposed to the virus and develop a robust immune response, or none at all. Similarly, a person can be fully vaccinated and still contract a breakthrough infection.

As noted, the debate about what provides the most robust immune response – infection or vaccination – is not settled.

Still, we haven’t paid enough attention to the status of those who have contracted COVID-19 and recovered. (At least 1.85 million Canadians are known to have been infected.) Some countries consider prior infection to be the equivalent to at least one shot. Canada, with the exception of Quebec, does not.

The durability of immunity matters a lot too. Protection from vaccines seems to wane after about six months and that’s why boosters are being promoted. That doesn’t mean vaccines don’t work, it means they have limitations.

What we do know is that people who are vaccinated are less likely to suffer from severe illness and death. Hospital admissions, especially those in intensive care, are predominantly unvaccinated patients.

The great unknown today is how immunity – regardless of how it’s acquired – will hold up against variants like Omicron.

To date, it looks like the new variant can evade antibodies to a certain extent. That will result in more infections, even in the vaccinated, at least until we can tweak vaccines (which, thankfully, is possible with the mRNA vaccines).

But there is also growing evidence that the infections will be less severe, especially in those who are vaccinated with at least two shots.

That’s why there is a push for people to get third doses. The more shots you have, the better your immunity will be. It might also be longer lasting, but we don’t know.

Will we require annual COVID-19 shots in the future? Perhaps. But that’s not the end of the world. We already have annual flu shots.

COVID-19 is here to stay. It’s in our interest, individually and collectively, to bolster our immunity as best we can because that will minimize illness and death.

Ultimately that’s what matters.

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