HowToBestRollOutThe
VaccinationsVille
There has been a lot of talk recently about the 'one dose of the Covid vaccine' approach to get it into as many people as quickly as possible.
The hot take media's ginning up of bad news after one dose has also begun and will no doubt only get worse.
But what do we actually know about single jab efficacy?
As Derek Lowe explains over at 'Science Translational Medicine Blogs', very little:
"...How protective is one dose?
We don’t know for (the AstraZeneca) vaccine, nor for the Pfizer/BioNTech one, nor for Moderna’s. No studies have been designed to find that out, so all we can do is guess based on what we’ve seen with the interval between doses in the two-dose studies. That’s been encouraging with the two mRNA vaccines, but remember: we don’t know how they are over a longer period, because no one was left without a second dose for that long. It’s certainly possible that without the second booster that the protection seen after one shot starts to wane. We do not know. And we know even less about the Oxford/AZ vaccine’s behavior under these conditions..."
So, what's driving this one dose approach and the rapid approval of the the adenoviral AstraZeneca vaccine in the UK?
Well, if the UK variant, which we discussed briefly here, is actually more infectious, potentially due to higher viral load, Mr. Lowe reckons that, purely from a public health point of view, there is likely great concern about the healthcare system being overwhelmed without a rapid vaccine-mediated tampdown:
...That situation in the UK appears to be one of the biggest factors driving the approval and rollout, and I see their point: this vaccine is indeed better than nothing, one shot for more people is likely to be better than two-shots-for-some, and it looks like they’re going to need all the help they can get. But “better than nothing” is a rough place to be....
______
...That situation in the UK appears to be one of the biggest factors driving the approval and rollout, and I see their point: this vaccine is indeed better than nothing, one shot for more people is likely to be better than two-shots-for-some, and it looks like they’re going to need all the help they can get. But “better than nothing” is a rough place to be....
______
And don't let that 'blog' tag fool you - As noted previously, Mr. Lowe has proven his bonafides around here.
.
.
4 comments:
I am not a scientist but I like and respect science, I do not , as seems to be the fashion lately, question every development, delay, new discovery, change or rethink that comes along. I am happy that science generally allows for bonafide new information to be incorporated into an existing theory or to change the thinking altogether.
Ross K. I know this type of science isn’t your area but with your experience would you think it possible they had some of the test participants only have one shot? How would they know to go the extra half to full dose. The information may not be official but I gotta think the vaccine developers would have some idea, although they may not want to say as much for good reason.
Saying that, it would seem to be best to do as has been found to be most effective. I’d worry that the virus may gain some strength against the vaccine if it were not given the full walloping.
I learned two things this morning Ross. Don’t comment on a blog on only a half cup of coffee and read the links contained in the blog post. Having had a second cup and read your links my question to you has largely been answered. Sorry for going off half cocked, if you did have anything to add it’s always appreciated.
No worries Graham - in future I'll do my best to flesh out the links a little more.
Thanks for weighing in with thoughtful questions - they are key and the answers truly aren't yet known.
I am assuming (and this is speculation on my part, which makes me a little nervous) that the expectation is that there would be some protection from the first dose and that a later than currently scheduled 2nd dose would then be a good thing once the manufacture and distribution of the vaccines switch into high gear.
There is a bit of concern with the adenovirus-based vaccines (i.e. the AstraZeneca one, not the Pfizer or Moderna RNA/lipid coat ones) with this strategy, however, in that a long wait for the boost could result in your immune system mounting an antibody/T-cell response against the adenoviral portion of the vaccine itself (as opposed to the SARS-CoV-2 spike protein target).
The potential immune response against the adenoviral vector led to one of the proposed 'explanations' for why folks in the original AstraZeneca trial who mistakenly got a lower/half first dose of the vaccine appeared to do better than those who received a full first dose.
Derek Lowe explained this....Here:
"...Remember, one of the things about a(n) (adeno)viral vector is that you raise antibodies not only to the (SARS-CoV-2 spike) protein that whose genetic message you’re delivering, but to the (adeno)viral vector itself. It’s not impossible that a lower dose the first time made subsequent antibody neutralization of the second dose less of a problem. But you’d need to prove that..."
.
There is this:
https://i.imgur.com/rb7KNmo.jpeg
Post a Comment