South Africa's Astra Vaccine Snub
Raises Serious Questions
A shot seen as a key tool in the Covid-19 fight has been
sidelined in at least one country. What are the implications?
By Bloomberg Opinion
February 9, 2021, 7:19 AM EST
A halt in the use of the Astra-Oxford vaccine in South
Africa is concerning, but there are still powerful tools in the virus fight.
Sam Fazeli, a Bloomberg Opinion contributor who covers the
pharmaceutical industry for Bloomberg Intelligence, answered questions about
the implications of South Africa’s decision this week to temporarily halt the
rollout of the AstraZeneca Plc-Oxford University vaccine after a trial showed
the Astra shot had limited efficacy against a new variant of the virus that
emerged there. In the meantime, the country will speed up its supply of shots
from Johnson & Johnson and Pfizer Inc.-BioNTech SE. The conversation has
been edited and condensed.
What’s the rationale behind this move? Isn’t the Astra
shot effective against the virus?
While AstraZeneca’s vaccine was found to offer good efficacy
against previous forms of the virus and even a more transmissible variant that
emerged in the U.K., it showed only 10%
efficacy in a relatively small trial of 2,000 subjects against mild and moderate disease caused by
the B.1.351 variant first found in South Africa. The data wasn’t able to
show whether the Astra vaccine protects against severe illness from this variant, though chances are it might. Johnson & Johnson’s vaccine did
show 85% efficacy against moderate
to severe disease in a much bigger trial, in which most of the Covid cases
arose from the variant. So presumably that’s why J&J’s vaccine is preferred
over Astra’s in South Africa.
So the data on the J&J shot and the B.1.351 variant from South Africa is still good
news, right?
Well, yes and no. An 85%
efficacy against severe or critical disease is great, but it still means
that 15% of patients did develop more serious Covid-19. This compares with
close to 100% efficacy for vaccine trials conducted in other geographies where
B.1.351 was not prevalent. Also, the efficacy of the J&J vaccine was 57%
against moderate to severe
disease. When you overlap those two, it suggests that a much lower efficacy
against moderate disease dragged it from 85% to 57%. While we don’t know
whether its efficacy would be as low as AstraZeneca’s vaccine when only looking
at mild-to-moderate disease, the data tell us it’s not going to be great.
Moreover, this leaves us with potentially two vaccines that leave at least
some people susceptible to severe disease while they are not preventing mild
disease, and by inference, a higher
risk of viral transmission.
What risks does this pose?
Continued transmission with even mild to moderate disease
brings two possible risks with it. One is that this allows the virus to
continue to mutate and evolve
more vigorously than if the vaccines had prevented mild disease, as they do for
the non-variant versions. There is also the risk that there will be a higher
rate of “long Covid” from
infections with the B.1.351 variant than non-variant viral infections. I say
this because there is probably a correlation between disease severity and long
Covid, though this still needs to be proved.
Can’t vaccines be adjusted to target a new virus variant?
This is true. I have often written about how fast the
vaccines using messenger RNA technology from Pfizer Inc.-BioNTech SE and
Moderna Inc. — as well as others from J&J, Astra and Novavax Inc., which
use different vaccine methods — can be adapted to any new variant. That is not
the problem. And some good news has just been published by the Fred Hutchinson
Cancer Research Center showing that people who were previously infected with
either an older version of the virus or the B.1.351 variant and then vaccinated
with the Pfizer-BioNTech or Moderna vaccines responded equally strongly in the
form of generating high antibody levels. The key finding was that the
vaccination induced antibodies that could neutralize a virus that was
engineered to look similar to the B.1.351 variant, telling us that the immune
system is not “blind” to this variant. But this does not tell us that future
new vaccines will be as efficacious as those developed against non-variant
virus. It is possible that a new-variant vaccine may run afoul of “original antigenic sin” – that is, even
as the immune system gets stimulated by the new vaccine booster shot, it may
actually produce a lot of antibodies against the original version of the virus.
This is all theoretical, but we can’t just assume everything will go our way.
Presumably there will be more variants. How can we stay
ahead of them?
To keep one step ahead of this virus, we have to vaccinate
as fast as possible to get that 85% efficacy that the J&J vaccine
showed against severe disease in our communities; while not bulletproof, it’s
still strong protection against the worst Covid-19 outcomes. We also need to
keep testing and routinely conduct full genomic analysis at a much bigger
scale on samples from around the globe, not just the U.K. and South Africa,
where the most troublesome variants were first spotted. This way, we can
identify outbreaks of B.1.351 or other new variants before they have taken root
in the community and it’s too late. Last, we should develop the next round of
vaccines as fast as possible and determine their potential for offering
protection as early as possible so we can adjust our expectations. This may
sound a little like doom and gloom, but it’s not. We do have vaccines that will
hopefully significantly reduce the burden of the disease on our societies and
health-care systems. What I am saying, though, is that we cannot just assume
that science will forever beat biology and evolution and that we should price
that into our expectations.
This column does not necessarily reflect the opinion of the
editorial board or Bloomberg LP and its owners.
To contact the author of this story:
Bloomberg Opinion at davidshipley@bloomberg.net
To contact the editor responsible for this story:
Beth Williams at bewilliams@bloomberg.net
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