[RcouF1uZ4gsC]

The mRNA vaccines have been the silver lining to the whole COVID-19 disaster.

They seem “unreasonably effective” against COVID, basically if you had a genie that you could ask to make a vaccine, it would be hard to do much better, other than the requirement for 2 jabs.

In addition, the mRNA technology has broad applicability to other issues such as other viruses (such as flu) and even cancer!

[dawnerd]

Traditional vaccines have also been "unreasonably effective". I'm all for mRNA going forward (I got pfizer myself) but lets not downplay just how effective the "old" tech has been against covid. It's really quite amazing how well we've been able to target it. Now if only we could get more people to accept that the vaccines are safe...

[zajio1am]

> Traditional vaccines have also been "unreasonably effective"

AFAIK not really. I know just about Sinovac and that was significantly worse efficacy than other vaccines. Note that adonovirusvector based vaccines like AstraZeneca one are not 'traditional vaccines' but also rather new tech.

[dawnerd]

That’s why I put old in quotes. mRNA is also nothing new, just new at this scale. People are just acting like it’s something that was just invented over the last year.

[armada651]

In your comment you implied mRNA is new tech though, you may want to clarify what you meant to say.

[armada651]

Which old tech vaccines? I haven't seen any attenuated vaccines for covid. Even the viral vector vaccines aren't exactly "old tech" and they are certainly less effective than mRNA vaccines.

Just like with mRNA; viral vector vaccines haven't been seen widespread use before COVID either. And the only attempts at an attenuated vaccine have been pretty ineffective as far as I know.

[dawnerd]

They're all pretty comparable. Novavax should be getting a lot more attention since it doesn't require super cold storage and appears to be on par with the mRNA vaccines.

https://www.yalemedicine.org/news/covid-19-vaccine-compariso...

[armada651]

Novavax does look promising, but I was mainly pointing out that there is currently no effective "old tech" vaccine in widespread use, it's all new tech.

I'm not saying that out of skepticism for these vaccines, I think it's amazing we're deploying all these new platforms. I just think saying that they're no more effective than vaccines we've had before is a misrepresentation of the facts.

[enterexit]

Does mixing of one mRNA vaccine with another mRNA vaccine for the second does create the same effect as if it's one brand of vaccine was used?

[raphlinus]

They are considered "interchangeable" by the National Advisory Committee on Immunization of Canada.

[1]: https://www.canada.ca/en/public-health/services/immunization...

[cwkoss]

Moderna and pfizer both encode the spike protein identically.

"Follow up earlier post. Here is moderna/pfizer/wild type spike. There is only 2 amino acids different from wild to vaccine. Same for both vaccines. The change forces the protein to look like it would when stuck to the outside of the virus, without needing the rest of the virus"

From Thought Emporium on twitter (cool biohacker with particular focus on genetic engineering, but amazing breadth into physical sciences as well - I highly recommend his youtube channel)

https://twitter.com/EmporiumThought/status/14081777241920675...

[bryan0]

CDC said it was "ok" to do so back in January. In Europe they studied mixing mRNA with non-mRNA doses (astra zeneca and pfizer) and that also appeared to work very well: https://www.pbs.org/newshour/health/a-mix-and-match-approach...

[polote]

Do we have any proof that the second dose is useful at all ?

[raphlinus]

There's very strong evidence, particularly against the Delta variant[1]. That paper cites a 33.5% effectiveness after one dose, compared to 87.9% after two doses of the Pfizer/BioNTech vaccine.

[1]: https://www.medrxiv.org/content/10.1101/2021.05.22.21257658v...

[giantg2]

That includes the lag time. A single dose is supposed to be about 80% effective once immunity develops. They don't know how long that will last and thus have the second shot to increase effectiveness and hopefully longevity.

[raphlinus]

It's likely that the 80% figure you mention was based on protection against "ancestral type" virus, as would have been measured in the main trials. The gap between first dose and second dose protection is larger for Delta variant than for other variants, as documented in the paper I cited.

[polote]

But the issue, is that if you had your first dose 2 days before being infected, you count as being infected after 1 dose.

We need to compare "1 dose, x days after first dose" and "two doses, x days after first dose" to compare the same thing

[raphlinus]

That is not consistent with the "Vaccination status" definition in the paper I cited. The tl;dr on that is that "first dose" starts 21 days after vaccination, and "second dose" 14 days after.

Also, to get a better sense of the timeline for vaccination effectiveness, take a look at a chart like this one: https://www.technologyreview.com/2020/12/10/1013914/pfizer-b...

[polote]

If you wait 21 days after the first dose, or 14 days after the second dose. Unless everyone had their second dose 7 days after the first one you still don't compare the same thing.

We need something like, 21 days after the first dose, and split the result between people who got one dose and those who got two. We also need to make sure that the repartition of ` age since first dose` is the same for the two doses group and the single dose group.

[Yajirobe]

Is it worth getting a third dose?

[haswell]

Yes, this was covered in the trials for both vaccines.

[bryan0]

pfizer trial showed first dose by itself was extremely effective. check out the chart here: https://www.businessinsider.com/how-well-pfizer-shot-works-a...

Much of the data comparing efficacy of 1 vs 2 doses doesn't wait until 10-days after the first dose, which defeats the point. That being said 2 doses is more effective, just not by as much as you'd might think.

edit: replaced the above link because it was pay-walled