Like many doctors on the front lines of the pandemic
I’m getting a lot of patients asking which vaccine I think is best.
And my answer is always the same:
The best vaccine is the first one you can get into your arm.
It might take a little convincing
but let me tell you why all the vaccines we have are excellent
and why they all perform about the same.
Let’s compare four vaccines approved in Canada
and being used across the world right now.
How do they work?
Pfizer and Moderna:
These were the first two vaccines out of the gate.
Both require two shots.
Both are mRNA vaccines.
mRNA is a molecule that our cells use to produce proteins.
In this case
they’ve built an mRNA that holds the code
for the spike protein of the novel coronavirus.
When that mRNA goes into our cells
our cells read the code
and produce the spike protein
which then triggers our immune system to make antibodies.
And in case you’re wondering
mRNA is a type of genetic material
but it’s not DNA
and it can’t do anything to alter your own DNA.
So those are the mRNA vaccines.
Now let’s look at AstraZeneca and Janssen.
The Astra vaccine requires two shots
but the Janssen vaccine requires only one.
Both of these use what’s called a viral vector.
In other words
instead of using mRNA to get our bodies to make the spike protein
they use a virus called adenovirus.
That adenovirus is harmless to us
but it’s designed to contain that same coronavirus spike protein.
And when our immune system is exposed to that protein
it creates antibodies
that protect us from COVID-19.
Now the big question on everyone’s mind:
Are they safe?
More than 600 million doses of these vaccines
have been administered around the word
Including more than six million here in Canada.
And as expected
about 1 in 10 000 people
have gotten severe allergic reactions to the shots
–and those have usually been people with a strong history of allergies.
But the good news is that if there are any other side effects
they’re extremely rare.
And what about those unusual blood clots with the AstraZeneca vaccine?
Well, they’re so rare that even if they are from the vaccine
your chances of dying of COVID-19 in this country
would be at least 50 times higher
than your chances of getting one of those blood clots from the vaccine.
Those risks may be different in people under 55
and more research is underway.
Now the vaccines will give you some arm pain
and a day’s worth of muscle aches
some fatigue, and even fever.
But those are actually good things
because it means your immune system is working.
How well do they work?
These are efficacy numbers.
In other words, how much less likely you are to get sick from the virus
if you’re vaccinated, compared to not vaccinated.
But the thing about these numbers is that they’re constantly changing.
For example, the AstraZeneca vaccine
was just found to be around 76% effective in the U.S. trial.
And those numbers are when the shot is given one month apart.
When you spread it to three months
it’s 81% effective.
And the Janssen vaccine averaged out to 67% across countries
but in the U.S., it was 72% effective.
But surely 95% has got to be better than 72%, right?
Actually, we don’t know.
And that’s because these studies were done at different times
and in different parts of the world.
Vaccines are less effective against the newer variants of concern
that are now here.
The Pfizer and Moderna trials were done when we didn’t have these variants of concern
whereas the AstraZeneca and Janssen trials
were done more recently
when variants had already begun to circulate.
Also, these are the numbers for the Pfizer and Moderna vaccines
when you get your shots 3 or 4 weeks apart.
What we don’t know how those vaccines will perform
when you get your shots 3 or 4 months apart
which will be the case for many Canadians.
So although 95% sounds better than 72%
that’s like saying the guy who scored 95% on a grade 10 math test
is smarter than the girl who scored 72% on an astrophysics exam.
The questions are so different that you just can’t know.
Now, having said all that
I’ll also tell you that those numbers aren’t even what we really care about.
These are the numbers that really matter.
This is how effectively each vaccine protects you against severe disease
things like ending up in hospital or dying from the virus.
So when it comes to the things that we really want to avoid
they all protect us really well.
So if you’re holding out for what you think is a better shot
you might just be refusing a vaccine that keeps you off a ventilator
in the hopes of getting one that might protect you better from getting the sniffles.
So if you’re lucky enough to be offered a vaccine, go get it.
The sooner we can all do that
the sooner we’ll get through this pandemic together.