What you need to know about Astrazeneca vaccine
HALIFAX — Recent studies have raised concerns about the effectiveness of the Astrazeneca vaccine against variants of the coronavirus that causes COVID-19, as well as possible side-effects such as blood clots.
The questions around this particular vaccine have prompted some Nova Scotians to ask whether they should wait for other vaccines to become available for their demographic.
Saltwire Network spoke to immunologist Dr. Gerald Evans of Queen’s University in Kingston, Ont., about these concerns. The following question and answer piece is condensed and edited from that interview:
Q: Some countries in Europe have suspended the use of Astrazeneca because studies have linked it to incidences of blood clots or thrombosis. Should people be worried about that?
A: I’ll start off by quoting William Shakespeare: this is much ado about nothing. It is readily apparent that the rate of thrombosis being seen in people who receive the Astrazeneca vaccine in a number of countries in Europe is in fact lower than the rate of thrombosis that is seen randomly in the general population. In other words, there is no added risk. It’s been picked up (by the media) because there’s been so much discussion about vaccine that people are looking for nuance within the concept of which one might be safer or not. It got traction, I think, because governments were suspending its use or they were saying a certain batch shouldn’t be used but really none of us who study these issues carefully, whether you’re a vaccinologist, whether you’re a hematologist interested in thrombosis, think that there’s anything at all to suggest there’s a causal link between the Astrazeneca vaccine and thrombosis, it’s not there.
Q: What about the effectiveness of Astrazeneca in battling the variants of the coronavirus that causes COVID-19 such as the South African and United Kingdom strains? A recent New England Journal of Medicine paper recently raised questions about its effectiveness against the South African strain (B.1.351).
A: I do know that the study was a rehash of what was talked about in February when this group initially did a press release saying they thought that the Astrazeneca vaccine wasn’t working and the South African government turned around and said it was suspending its use. Now that we have the data to analyze, it’s quite apparent this actually says nothing about efficacy. Because the group that they studied who received the vaccine — and were compared with the group that didn’t get the vaccine — were in fact a very young group of people (median age of 30). To be able to detect there’s a reduction in severe illness like hospitalizations and deaths, you wouldn’t expect to see a difference between a vaccinated and an unvaccinated group, with or without the variant.
What it tells you is that the vaccine may very well have protected some of these younger individuals from getting severely ill and hospitalized so all they ended up with was mild to moderate illness.
All of the vaccines (Astrazeneca, Pfizer, Moderna and Johnson and Johnson) prevent severe outcomes from COVID-19. All of them actually show that they’re really effective at preventing you from dying from COVID-19. This study from South Africa, although it’s done by a very reputable group of investigators there, wasn’t designed to show a reduction in severe illness. If so, they would have enrolled people who were much older.
Q: How much of a factor will these variant strains, which are believed to be more contagious, become as we continue to fight COVID-19?
A: In fact right now in Canada, certainly right here in Ontario, I can tell you over 50 per cent of the isolants that we’re finding are in fact variants, almost all of them by the way the B.117, the variant that arose in the U.K. We have not seen a lot of South African variants in our Ontario data nor across Canada. So, yes, there’s no question, B.117, is pretty well at the stage that it will become the SARS-COV-2 virus that’s causing all the infections (in Ontario).
If you have low numbers of cases, which is what’s happening in Atlantic Canada, which is what’s happening in my part of Ontario (Kingston), even when the variants arrive, the force of infections is quite low because community prevalence is low. It does bode well that Atlantic Canada may not be as affected by B.117 and the other variants but B.117 will eventually become the dominant strain across the globe, it is just replacing the original SARS-COV-2.
Q: Getting back to Astrazeneca and the people who are considering putting off their shots and waiting for Pfizer, Moderna or another vaccine what would you say to them?
A: The key message I would give to the public is, there is no difference right now in the efficacy of these vaccines. All of them will protect you from death. The problem you have if you want to delay it is that you run the risk of having no vaccine and if you get COVID19 and you have certain factors whether you’re older or some other problem medically, then you’re putting yourself at great risk.