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COVID-19 – Page 2 – deonandia


COVID-19: Does a 4th Vaccine Dose Prevent Infection?

by Raywat Deonandan, PhD
Epidemiologist & Associate Professor
University of Ottawa
(I add my credentials to these COVID-19 blog posts in case they get shared. I want readers to know that my opinion is supposedly an educated and informed one)

Earlier this year, I wrote a post explaining how prior to the rise of the Omicron variant, COVID-19 mRNA vaccines were actually not bad at preventing both infection and transmission of the disease. Hence the strong evidence base for policy measures like vaccine mandates at work and vaccine passports at places like restaurants.

Omicron changed all that to a high degree by greatly reducing the vaccines’ ability to curtail infection and transmission, but not their ability to provide strong protection against the worst measurable COVID outcomes, like hospitalization and death.

That analysis was based on the assumption that most people had received only two doses of the vaccine. But I ended that post by citing some evidence showing that a third dose restored much of the jab’s effectiveness at preventing infection.

As I write this, that original Omicron strain has been supplanted by more transmissible subvariants. Currently, the BA.4 and BA.5 subvariants account for the majority of cases in North America. Both subvariants show an ability to overcome immunity garnered from both vaccination and prior infection from Omicron, suggesting that even three doses are no longer effective in preventing infection and transmission.

We are now in the era of 4th doses. So I thought it would be helpful to revisit the evidence around whether four doses can help prevent infection.

Spoiler alert: the evidence, as it is, suggests that four doses definitely increases our ability to avoid infection altogether. But there is debate about exactly how much that increase is, and how long it will last.


Monkeypox… More Than Just an Excellent Name for a Band

by Raywat Deonandan, PhD
Epidemiologist & Associate Professor
University of Ottawa

(I add my credentials to these COVID-19 blog posts in case they get shared. I want readers to know that my opinion is supposedly an educated and informed one… But wait! This is not a COVID-19 post.  And yet…. the credentials still remain relevant here. Sigh.)

As the title suggests, today’s topic is monkeypox. My inbox is blazing hot with dozens of media requests to come on-air and talk about this disease. So I thought I’d get ahead a bit and write what I know first, as I am certainly not a monkeypox researcher or expert.

I remember when I first gave monkeypox more than a passing thought. It was when reading a paper listing the likely candidates for a world-stopping global pandemic. The paper was written before the COVID pandemic. I wish I could find it now!

As of today, there are 36 suspected cases in Europe (UK, Portugal, and Spain), one in the USA, and a whopping 13 in Canada. (UPDATE: since I wrote this sentence a few hours ago, the disease has spread to Italy and Sweden.)

So, what is this disease, and should we be worried?  Let’s break it down. (more…)

COVID-19: Why Should the Vaccinated Care That the Unvaccinated Are Unvaccinated?

by Raywat Deonandan, PhD
Epidemiologist & Associate Professor
University of Ottawa

(I add my credentials to these COVID-19 blog posts in case they get shared. I want readers to know that my opinion is supposedly an educated and informed one)

As I write this, my home of Ottawa –and some other parts of the country and the world– is under siege by a fraction of the population who believe their rights are being infringed by rules designed to improve public health, most glaringly the rules around mandatory vaccination for some professions or some activities.

Presumably most, or at least many, of the protestors are unvaccinated and are directly affected by these rules. But a fair proportion are vaccinated and support the “right to choose.”  Their argument is that it should not matter to the vaccinated whether or not others choose to accept vaccination.

Theirs is a flawed argument. There are multiple reasons that vaccinated people are better served by (a) encouraging more people to become vaccinated, and (b) not wishing to mingle too often with the unvaccinated. Below, I list a few of those reasons.

But first, there are  two important facts to consider. The first fact, as we all know, is that vaccines are not 100% effective at stopping transmission and serious disease. This is especially true for the COVID vaccines in the wake of the Omicron variant. While Omicron has compromised the ability of two doses to prevent actual infection, a third dose greatly restores such protection. (See my earlier post on whether the vaccines still prevent transmission.)

The second fact is that the more unvaccinated people there are in the community, the more opportunity there is for rampant transmission within those groups. While Omicron has compromised the vaccines’ ability to curb transmission with only two doses, it still remains true that outbreaks are more likely to happen among unvaccinated groups. The Ontario Science Table estimates the risk of infection among the unvaccinated to be more than twice that of the vaccinated.

With that said, here are five reasons the vaccinated care that others are not yet vaccinated:

1) The more people who become vaccinated, the more community immunity we have. With Omicron so hyper-contagious, it is unlikely that we can reach true herd immunity. But every person who accepts full vaccination is a bulwark against transmission penetrating into the community. That greater transmission means that our vulnerable loved ones, like children who cannot be vaccinated, or the vaccinated elderly who remain at higher risk for bad outcomes and death, remain at unnecessarily high levels of vulnerability. The more people that get vaccinated, the lower this risk.

2) Less penetration into the community means that the vaccinated will experience fewer breakthrough infections. And while vaccines offer great protection against infection, hospitalization, and death, that protection is not absolute. So every time the risk of breakthrough infection is raised, the risk of a vaccinated person becoming hospitalized or dying also is raised. The more people who get vaccinated, the lower this risk.

3) The unvaccinated are “dry tinder” for the runaway fire that is COVID-19. They are more likely to become infected, seriously ill, hospitalized, and to die. Recent data from Public Health Ontario show that the unvaccinated over 40 have over seven times the risk of dying from COVID than do the vaccinated. In fact, in some age groups, the relative risk of dying from not being vaccinated is greater than the risk of getting lung cancer from smoking.

According to the Ontario Science Table, the unvaccinated have 6 times the risk of being hospitalized than do the vaccinated (2 doses), and over ten times the risk of ending up in the ICU. Therefore, the unvaccinated are more likely to eat up precious health care capacity that the rest of us need for non-COVID emergencies. The more people who get vaccinated, the lower this risk.

4) Due to both the higher likelihood of being infected and the higher likelihood of carrying a higher viral load, some studies suggest that the unvaccinated pose a higher infection risk directly to the vaccinated. As the authors of one pre-print study concluded, “while risk associated with avoiding vaccination during a virulent pandemic accrues chiefly to the unvaccinated, the choices of these individuals are likely to impact the health and safety of vaccinated individuals in a manner disproportionate to the fraction of unvaccinated individuals in the population.” In fact, the authors computed that the unvaccinated raise the risk of infection for the vaccinated by a factor of over six, beyond, of course, the risk that they themselves pose to other unvaccinated people.

5) We love you and don’t want you to suffer and die.

Those who wish to frame this debate as one around personal choice are not incorrect to do so, in the broadest sense. But they are wrong to suggest that the actions of those who choose not to vaccinate do not affect the rest of us. Quite the contrary.


Let’s Talk About RAT Tests (Podcast Episode)

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