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Sunday, May 19, 2024
Dr. Brown: With Omicron dominating, be careful this holiday season

Where SARS-Cov-2 is concerned, surprise is the operative word. As recently as last summer some experts began to imagine a world beyond COVID or at least a world where COVID was corralled well enough to begin opening up.

Then three things went wrong.

First, the anti-vaxxers dug their heels in, so the pandemic simmered and flared up throughout much of the Western world and beyond.

Second, the Israelis and Qataris discovered that the effectiveness of mRNA vaccines began to wane four to five months following the second shot, with the result that some of the fully vaccinated developed breakthrough infections, which occasionally were severe enough to warrant hospitalization.

Third and most worrisome, what many virologists feared most might happen: A new, potentially dangerous mutant version of the virus emerged a few weeks ago. It turned out to be even more transmissible than Delta and perhaps capable of skirting the antibody responses provoked by vaccines or earlier natural infections. The Omicron variant had entered the fray.

More than any previous variant, Omicron is literally armed to the teeth with over 50 mutations, far more than earlier variants, 30 of which involve the spike protein.

Some latter mutations, because of their strategic location, might facilitate the virus’s chances of locking onto ACE-2 receptors in the host cell’s membrane, and perhaps, cloaking the spike protein from the body’s antibodies. On the positive side there’s no evidence that T cell immunity is impaired.

It’s too early to say whether the worst fears of virologists and infectious disease experts are justified. So far, the variant appears to be infectious enough to displace the Delta variant and, at least in laboratory tests, it appears to be less responsive to antibodies created naturally or in response to vaccines. But at least among the young, the associated clinical illness appears to be mild.

It will take several weeks before we know for sure whether this highly transmissible variant causes more severe infections in the wider population. But even if the virus proves no more lethal than Delta, transmission to more people, means more cases and deaths.

Most experts expect current vaccines to remain effective, but less so, with only two jabs – hence the added push for booster shots these days. Recently Pfizer announced that a version of its current vaccine, engineered to deal with the Omicron and other variants, could be available by the spring of 2022. That’s one of the pluses of mRNA vaccines such as Pfizer’s and Moderna’s products – quick adaptations to changing viral antigenic targets.

Hopefully, Omicron will turn out to be relatively benign despite its many mutations, but it is worrisome, because each new variant appears to sport more mutations – somewhat like an arms race between the virus and our defences such as vaccines, monoclonal antibody treatments and most recently antiviral drugs.

So far, the virus is more than holding its own, especially against the unvaccinated and much less success against the fully vaccinated. The reason is an ancient one, evolution on the part of the pathogen (in this case by natural selection acting on random mutations in the virus) and naturally acquired adaptations on the part of human and other animal hosts.

This is mightily aided in the case of humans by vaccines and soon antiviral drugs, both of which, like the annual flu vaccine, will have to be regularly updated. It’s a long game and we’re barely through the first innings.

With more indoor activities and a certain rebelliousness and resistance on the part of many to continue social distancing and masking, this winter, like last year's, could be one to remember. Let’s hope not but be prepared to adjust.

Luckily, unlike last winter, most are now fully vaccinated, and many have received a booster. That’s a big plus but remember the vaccinated may develop breakthrough infections and spread the virus to the vulnerable.

Be cautious and enjoy the holiday season.

Dr. William Brown is a professor of neurology at McMaster University and co-founder of the InfoHealth series at the Niagara-on-the-Lake Public Library.  


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