CATEGORY / epidemiology

COVID-19: Even More Q&A

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)

Today’s post is a bit of a hodgepodge of topics people have been asking me to talk about. Let’s begin with a question from a concerned citizen, who asked:


COVID-19: Answering Your Questions

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 has been the norm these past 15 months, I’ve been getting a slew of regular COVID- and vaccine-based questions from the general public. There are a few I’d like to answer in this public space.

And I want to start with questions asked by a class of 5th graders who recently invited me to do a Q&A in their school.



1. Does Covid 19 deserve the title “a plague”?

Well, there is no scientific definition for “plague”, but it’s generally understood to be a bacterial infection. And most people think of the Bubonic Plague, which was definitional a bacterial thing. One online definition says a plague is, “a contagious bacterial disease characterized by fever and delirium, typically with the formation of buboes ( bubonic plague ) and sometimes infection of the lungs ( pneumonic plague ).”

Since COVID is caused by a virus, I would say the answer is…. no.

2. Do you think the vaccine will completely get rid of Covid 19

The answer is no. I gave my reasons in this earlier post, “Can We Eradicate the Virus?

3. What was the worst pandemic in human history?

Well, that depends on what you mean by “worst”. The most impactful? The longest lasting? The most damaging? The one that infected the most people? Or the one that killed the most people?

Focusing on the last, we see that COVID has killed about 3 million people that we know of. But HIV/AIDS has killed over 35 million. The Plague of Justinian might have killed 100 million. And maybe the Black Death killed 200 million. So your guess is as good as mine.

4. How long did it take for the Spanish Flu to stop affecting people? Why did it stop if there were no vaccines?

In order for a pandemic to end, the disease has to reach a point at which it is unable to find enough hosts to catch it, i.e. susceptible people. We usually reduce the number of susceptible people by vaccination. But it could happen through infection, recovery and/or death as well. 

By the end of the Spanish Flu pandemic, maybe a third of the world’s population had caught it. So the number of susceptible people might have been small enough to halt its spread. But another thing also happened. The 1918 strain began to evolve via a process called “antigenic drift.” Versions came back in the winters of 1919-1920 and 1920-1921, but they were much less deadly.

Every so often, direct descendants of the 1918 flu combined with bird flu or swine flu to create powerful new pandemic strains, which is what happened in 1957, 1968 and 2009.

So the Spanish Flu was likely stopped by a combination of mutation and population immunity through recovery.

5. If you were born and your mom had Covid 19, will the baby have antibodies?

There are limited data. But it looks like at least some will.

6. Will it make my dad’s farts smell different?

Yes. Because your Dad will lose his sense of taste, and will therefore eat blander foods, thus changing his farts qualitatively.


Now here are some questions sent by a concerned citizen who forwarded to me some of the things he is hearing in his community:

1. I’m young and healthy and have a good immune system, I will handle Covid 19 just fine.  Why should I take the vaccine and risk any side effects?

Plenty of young, healthy people with good immune systems end up in the hospital for this disease, and some die. So you’re not bulletproof.

But the biggest reason to get jabbed is that you will contribute to herd immunity. If you get infected, you can pass it on to someone else who might not be young and healthy. Getting vaccinated greatly reduces your chances of getting infected and passing it on to someone else.

And if protecting others doesn’t motivate you, keep in mind that as long as the disease is circulating to a high extent, things will be closed, masks will be normalized, and life will be crappy. We need as many people as possible –even young, health ones– to become vaccinated so the disease goes away and everything can go back to normal.

So this is how you get your fun things back. Get jabbed.

2.  What are the long term effects of the vaccine?  I’m very scared that it will cause cancer or something in the future.

Well no one knows because we’ve only had the vaccines for about a year. But hundreds of millions of people have been jabbed, and nothing bad has happened to the overwhelming majority of them.

If you eat fast food or breathe city air, your risk of cancer from those things is thousands of times greater than the risk posed by the vaccine. So if you don’t feel a great urge to only eat organic vegan food and walk around with your own oxygen mask, then I question the consistency of your fear calculus.

I don’t mean to minimize your anxiety…. but I kind of do mean to. There is always some risk here. I just ask that you look around your life and honestly appraise whether you apply the same conservative thinking consistently.

3.  We are being told that even if we are vaccinated we still have to wear masks, social distance, etc.  So there’s nothing in it for me.  Why then would I take the vaccine?

What you’re not being told is that you only have to wear masks and distance for a short period of time after getting jabbed. Here’s why. Vaccination doesn’t offer 100% protection, but something closer to 95%. That only matters if the disease is highly prevalent. If it’s all around us, then it will find holes in our defences and capitalize on that 5% failure.

So we get vaccinated to slow transmission and wear masks, etc, to get protection up to 100% while the incidence rate drops. Once the rate has dropped, it becomes unlikely that the disease will find holes. Then we doff the masks permanently.

How long will that take? Weeks to months. Depends on where you’re starting from.

I describe this in more detail in my earlier post, “Why The Vaccinated Can’t Throw Caution To The Wind

4.  The side effects of the vaccine are worse than Covid 19, so I won’t take that risk.

Really? Let’s look at Ontario data. As of May 15, 2021, we’ve given about 5 million Pfizer shots, out of which there were a mere 57 serious adverse events. Of those, there were 3 deaths, none of which were thought to have been caused by the vaccine.

But even if you do believe that they were caused by the vaccine, that works out to a risk of death of 0.00006% from the vaccine, and a risk of serious side effects of 0.001%.

Now, the infection fatality rate of COVID the disease is controversial. Most of us peg it at around 1%. But some people who downplay its seriousness would say it’s more like 0.2-0.4%. That’s your chance of dying if you get COVID.

Okay, if the latter are correct (and they are not), then the risk of death from COVID is over three thousand times greater than the risk of death from vaccine. Frankly, it’s probably more than twice that amount.

5.  The government is using the vaccine to control us.

Guess what? The government has better tools to control us. Ever heard of taxes, speed limits, and the police force?

6.  We don’t know what the plan is, if we will need to keep getting these shots or how often.  How can I trust this when they don’t even know what we will need to do in the future?

This is the price of being an adult. Sorry if that comes across as flippant, but scientists don’t know everything. Doctors can’t cure everything. There is uncertainty in the world. This is has always been the nature of life.

We are faced with an unprecedented global emergency, and by some miracle the smartest people on this planet have found us a solution. But those same smart people aren’t gods. They don’t know the future.

I understand that you want certainty; we all do. But this is what real life is about: making important decisions based on imperfect and incomplete information.

No one can promise you everything will be okay. We can only give probabilities and our best guesses.

7.  The vaccine is EXPERIMENTAL.  It’s not registered and anyone who takes it is a guinea pig and participating in a big experiment.  I’m going to wait and see what happens.

I’m not sure what “registered” means. The vaccines are the most scrutinized medical products in the history of human civilization. They have gone through all the same steps as every other drug your doctor has prescribed to you. No corners were cut.

The only difference is that because of the acute public scrutiny, you are aware of this vaccine and its regulatory path. You aren’t aware of the flimsy regulatory and testing process around your workout supplements, hair conditioner or chocolate bar. I guarantee you that those products did not go through multiple clinical trials of tens of thousands of people in dozens of countries, and had their data pored over by teams of scientists and journalists publicly in every corner of the world. The COVID vaccines did undergo that level of scrutiny.

How long do you want to wait? The vaccines have been injected into hundreds of millions of people now, with over six months worth of post-market data, and over a year of total clinical data.

There is nothing “experimental” here. The experiments were done a year ago, on animals and on tens of thousands of clinical trial subjects. Th mRNA and viral vector vaccine platforms have been years in the making; they just culminated this year as a result of intense resource allocation and budgetary focus.

Frankly, I’m much more terrified of the long term cancer, heart disease and diabetes-causing impacts of processed foods than I am of the miniscule risk posed by COVID vaccines.

Having said that, the risk is not zero. Everyone wants certainty of absolute safety, and that does not exist. Again, it’s the price of being a grown-up in a modern world: we have to make difficult decisions without guarantees.

So I am sympathetic to people’s fears. And I don’t want to minimize risk. But do consider all mindless risks we take on an hourly basis that we accept reflexively. And take some time to read the warning label on a bottle of aspirin or some other over-the-counter medication you happily accept.

Man, I sound irritable this evening!

COVID-19: Should You Give Your Child the Vaccine (Podcast Episode)

May 28, 2021 — It’s a question I get a lot these days: should I give my child the COVID-19 vaccine? Well, it’s ultimately a personal decision that you should take up with your child’s pediatrician. In this brief episode, I outline a framework for how to think about risk vs reward. You can read my full take on the question at this blog post: “COVID-19: Should I Vaccinate My Child?

This episode is also available as a YouTube video:


COVID-19: Should I Vaccinate My Child?

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)

Image borrowed from


Someone recently asked me to comment on COVID vaccination and children, specifically to offer guidance on whether they should get their child vaccinated.

Here’s the thing: I’m not comfortable telling parents whether or not to vaccinate their children against this disease. This is ultimately a personal choice, and is qualitatively different from the well established pediatric vaccines, like those for polio, rubella, diptheria, rotovirus, and measles, all of which I will heartily encourage your child to receive.

Instead, I will offer an approach for how to navigate this decision for yourself.

As always, I offer this disclaimer: I am a PhD scientist, not a medical doctor. So I cannot and will not offer clinical advice. As well, I own shares in all of the companies that manufacture COVID-19 vaccines for Canada. (Worth hundreds! Hundreds of dollars!) And I have done paid consulting work for many drug companies, most recently for AstraZeneca for whom I served on a medical advisory panel to react to their vaccine efficacy and safety data. If this disclosure compels you to discount my opinion on these matters, that is certainly your right.

Ultimately, this is about balancing risk vs reward. Specifically, how do we weigh the risk posed by the vaccine vs the reward offered by vaccination?

So let’s break it down like that.


1. Risks Posed by the Vaccine

Presently, the only COVID-19 vaccine authorized in Canada for use in children is that made by Pfizer.

Their recent trial enrolled 2,260 American kids aged 12-15. A total of 18 COVID cases were observed in the trial, all of which were in the placebo group of 1,129 people. None of the 1,131 people who got the vaccine contracted the disease.

This means that, according to these data, the vaccine has 100% efficacy on adolescents. Follow-up showed strong immunity a month after the second dose.

100% efficacy! That’s astounding. But do remember that it was found to be 95% efficacious among adults, so this isn’t too surprising. And real life effectiveness will always be a little less than trial-computed efficacy. So this number will come down as millions of kids are vaccinated.

(Pfizer and other companies are presently pursuing studies on children as young as 6 months. But no data are yet available for that cohort.)

While the full data have not yet been published, no serious safety signals have yet been indicated. Do remember, though, that there were only two thousand or so children in this trial. As millions become vaccinated, rarer effects will be observed. This is to be expected, but of course is not necessarily comforting.

But we can look at how the vaccine has been experienced by adults to get a good sense of how children will react. And tens of millions –possibly hundreds of millions– of adults have taken the Pfizer jab.

So what do we know about the safety of the vaccine among adults? Let’s look at Ontario data. Out of almost 5 million doses of the Pfizer vaccine given as of May 15, 2021, there were 57 “serious” adverse reaction reports. That works out to about 0.001% of injections resulting in a serious event.

What’s a serious event? One that “results in death, is life-threatening, requires in-patient hospitalization or prolongs an existing hospitalization, results in persistent or significant disability/incapacity, or in a congenital anomaly/birth defect”, according to the WHO standard definition.

In the Ontario adverse reaction data, three of the 57 were deaths. Yikes. That’s not good, right?

But hold on: “One report of death occurred in a resident of a health-care institution with significant co-morbidities. The cause of death was not attributed to the vaccine. The second report of death occurred in a community dwelling senior with complex cardiovascular and renal conditions, wherein the [adverse event] may have contributed to but was not the underlying cause of death. The third report of death occurred in a community dwelling senior with multiple comorbidities including heart disease and an autoimmune disorder. The cause of death was not attributed to the vaccine.”

In other words, none of the three deaths were caused by the vaccine. And even if they were, it would work out to a risk of death of 0.00006%.


2. Rewards Offered by the Vaccine

Now this is a little trickier to compute. We all know by now that children who contract COVID-19 are far less likely than adults to develop symptoms, to be hospitalized, and to die. The risk of the disease to them is very small… but not zero.

Though the infection fatality rate for young people is very small, we still expect that for every million 12-15 year old who contracts this disease, 20-30 will die from it.

This works out to a risk of death if you get COVID of 0.003%, which while vanishingly small, is still at least 50 times greater than the risk of dying from the vaccine.

But there are two remaining issues. First, this isn’t just about death, but also about illness. And second, the risk of death or illness from COVID must be multiplied by the probability of actually getting COVID in the first place.

In the USA alone, there have been thousands –nay, tens of thousands— of children hospitalized for COVID. We should not become overly comfortable with our children becoming infected with this virus.

As Gideon-MK puts it, “So the acute to children risks are relatively low. They are a bit higher than the risks from regular seasonal influenza, a bit lower than the risk of some of the nastier childhood diseases like measles, but they are much lower than the risks that adults face from coronavirus infections.”

It’s that second part that confounds me: what is the risk of your child contracting COVID in the first place? This is the most important metric in my mind, and I don’t have a good answer for you. It comes down to the incidence rate. Is it low enough?

We all agree that the best way to keep children safe from this disease, especially in schools, is to keep it out of the community in the first place.

If the incidence rate is high, then the probability of your child encountered an infected person is high, therefore their probability of becoming infected is high. As that probability approaches 100%, the more the risk of death approaches the IFR of 0.003%. But if the incidence is low, then the probability of getting the disease is also low, and the risk of death approaches zero.

So the risk of death –and of illness– hinges on how much disease is currently in the community. As adults become vaccinated, and as our strong mitigation efforts bear fruit, it seems highly likely that the incidence rate will drop fast in most parts of Canada.


3. What About Herd Immunity?

Well now we’re into another realm. The risk of the vaccine harming your child is really really small. But the risk of your child being harmed by COVID if the incidence rate is low is also really really small. So what’s the tie breaker?

Some will argue that the tie breaker is that vaccinated children contribute to herd immunity.

If we assume that herd immunity for COVID-19 kicks in at the point at which 75% of the population has immunity, and that our vaccines are 95% effective, then 80% of the Canadian population must be fully vaccinated for this magical threshold to be reached.

Guess what the percentage is of Canadians who are adults? Yep, about 80%.  This means that 100% of adults would have to accept vaccination before we can have the herd immunity conversation. And as we all know, there is sufficient vaccine hesitancy an skepticism that getting 100% acceptance is nigh impossible.

So if children were also vaccinated, our chances of achieving that magical goal go up substantially.

Really, this to me is the most compelling reason for pursuing vaccination among children. It’s not necessarily to protect the children, who have a very small overall COVID risk, but rather to protect other people. Those other people might be an unnamed greater population who benefit from herd immunity, or it might be the relatives of these children who have a higher risk profile than the children themselves. Though it is assumed that these relatives would themselves be vaccinated.

The ethical pushback against this mindset is that we have no other precedent that I can think of wherein we ask children to accept a risk —albeit a vanishingly tiny risk– to protect others from a disease that poses a similarly vanishingly small risk to the children themselves.

There is another ethical issue having to do with why low risk children are eligible for vaccination at all when there are still unvaccinated seniors among us in parts of the world where the disease is raging, and while there are seniors still awaiting their second doses in places like Ontario.

But for the parent, this comes down to a decision based on individual risk vs individual reward. As noted, I am reticent to offer explicit advice on this matter. I just hope my thoughts here have been useful in helping to understand the issues. For a deeper dive into this question, I recommend Gideon M-K’s full post on the issue, “Vaccinating Children Against Covid-19: Should we be protecting kids from coronavirus infections?

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