Welcome to another MedCram COVID-19 update. We're going to talk about the AstraZeneca COVID-19
vaccine, otherwise known as Covashield or Vaxzevria, which is a vaccine product that is not available
in the United States, but is available in several countries around the world, and it is a product
of AstraZeneca and Oxford university. For those of you don't know, it is similar to the johnson &
johnson / janssen pharmaceuticals vaccine in that it uses a vector from an adenovirus. In this case, it's
a chimpanzee adenovirus and we have a video that goes over all of this if you want some
more background on this information what we're going to do here in this video is update you on
what's happened since this has been approved in several countries and what is the evidence
of its efficacy and what's going on right now in terms of the latest research and development
and this data was taken from a couple of publications, one specifically that was
published in the Lancet that looked at data from Scotland and represented about 99 percent of the Scottish
population at 5.4 million people. And the other one was a retrospective study that was published on a
preprint server that has not been peer-reviewed, but evaluated in a retrospective cohort the
effectiveness of the AstraZeneca vaccine in terms of the efficacy of this vaccine. As you can see
for the alpha variant there was an 86 percent efficacy against hospitalization in the alpha variant.
In the gamma variant it was 87 percent effective, and in the delta variant up to 92 percent
effective at preventing hospitalization after the second dose. Not much data was reported for
the beta variant, which was the primary variant early on in 2021 in South Africa. For the delta
variant, though, the prevention after the second dose of symptomatic infection was only 61 percent.
One of the issues with the AstraZeneca vaccine early on that was discovered in about March of
2021 was the issue of blood clots similar to the johnson johnson vaccine. This caused a pausing
of these vaccine campaigns in many countries in Europe and you can see that today even there are
a number of countries where usage has stopped. For instance in Norway and also in South Africa.
Other countries have limited AstraZeneca to higher risk populations like the elderly and
that is because of the European Medicines Agency finding. And the European Medicines
Agency is the agency in charge of the evaluation and supervision of medicinal products in Europe.
The known risks of this vaccine is that there are unusual blood clots associated with it with low
platelets, which are estimated to occur in 1 in 100,000 vaccinated people, and so as a result of
this, there were a number of people earlier in 2021 that got the first dose of the AstraZeneca vaccine,
but did not get the second dose, because of the pausing this opened up an interesting and unique
opportunity to see what would happen if these subjects with the first dose being AstraZeneca
had a different type of COVID vaccine, for instance an mRNA vaccine, as their second shot.
And as it turns out, there have been a number of studies that have looked at this, and the results
are interesting. This paper, which was published in the Lancet on the 18th of October, 2021
looked at the effectiveness in different groups of vaccinees in Sweden. They looked at those who got
the first dose of the AstraZeneca vaccine followed by the Moderna vaccine or the Pfizer vaccine
or another dose of the AstraZeneca vaccine, and of course we'll put a link in the description below.
The three groups were the AstraZeneca vaccine first coupled with the Pfizer-BioNTech vaccine,
and in that group there was 94,569 people. In the AstraZeneca-Moderna group
there was sixteen thousand four hundred and two, and then finally the last group was the
astrazeneca-astrazeneca, in which there was four hundred and thirty thousand one hundred.
So you can see here the first dose is always astrazeneca and the second dose is changed up,
and the endpoint that they were looking at here was symptomatic covid19 infection, so the number
that they came up with for the astrazeneca-pfizer was 67 percent effectiveness with a 95 confidence interval.
59 percent to 73 percent for the astrazeneca moderna, they came up with in the calculation 79 percent
effectiveness or efficacy with 62 percent to 88 to 95 confidence interval, and then finally the
astrazeneca they found to be at 50 percent with a 95 confidence interval of 41 to 58.
Now if they combined this as these are the different second dose to the first or heterologous,
they found that the effectiveness or the efficacy here was 68 with a 95 confidence interval of
61 to 74 percent. So how did this change the evidence we have known based on studies that
have been done before that? Adding the Pfizer or the Moderna vaccine to the Astrazeneca vaccine
elicits a stronger immune response compared to a homologous astrazeneca astrazeneca vaccine
schedule. However what we didn't know up to this point was whether or not that translated into
a better efficacy for the vaccine. So just to be clear on that point, higher antibody levels doesn't
necessarily correlate to better immunity from the vaccine, and while high antibody levels is a good
sign, what we really need to see to prove efficacy is a trial in the real world. So as the authors
state "in this study the heterologous COVID-19 vaccination using the astrazeneca vaccine as the
first dose followed by either the Pfizer-BioNTech or the Moderna as the second dose was associated
with a 67 to 79 percent effectiveness against symptomatic COVID-19 infection,
and of course this was significantly higher than the 50 percent effectiveness from the homologous
vaccination schedule using just astrazeneca for the first and the second dose. I just wanted you to
be aware that the current vaccine from astrazeneca for covet 19 is officially known as azd1222,
but currently astrazeneca is in phase 2 and phase 3 trials on a brand new vaccine known as
azd2816, and this has a different spike protein
and it is modeled after the beta variant which is known as the b1351
that was seen in south africa. So I hope you found that this was helpful.
For more information, don't forget to follow us at MedCram.com. Thanks for joining us.