Axios: Pfizer Vaccine 42% Effective Against Delta

[9S_]

Via Axios

New data on coronavirus vaccine effectiveness may be "a wakeup call"

Driving the news: The study, conducted by nference and the Mayo Clinic, compared the effectiveness of the Pfizer and Moderna vaccines in the Mayo Clinic Health System over time from January to July.

• Moderna was 76% effective against infection, and Pfizer was only 42% effective [against July’s dominant strain: Delta]
• The study found similar results in other states. For example, in Florida, the risk of infection in July for people fully vaccinated with Moderna was about 60% lower than for people fully vaccinated with Pfizer.

https://www.axios.com/coronavirus-vaccines-pfizer-moderna-delta-biden-e9be4bb0-3d10-4f56-8054-5410be357070.html

Edited August 11, 2021 by 9S_
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[JamesE]

This is interesting. I wonder what the difference is as both vaccines are full-sequence segments for the spike protein.

[NumbNut]

3 hours ago, JamesE said:

This is interesting. I wonder what the difference is as both vaccines are full-sequence segments for the spike protein.

Yes they're both mRNA vaccines, but there has been one mRNA failure I'm aware of, the CureVac vaccine, with an efficacy less then 50%. I think they've stopped development on it

[MrStretch]

Note, these numbers are "against infection".

They are both still very efficient in preventing serious illness or hospitalization. 

[SomTum]

7 hours ago, JamesE said:

This is interesting. I wonder what the difference is as both vaccines are full-sequence segments for the spike protein.

In the preprint they do speculate on vaccine dosing as a possible explanation:

Quote

BNT162b2 is administered as 30μg/0.3mL (100 μg/mL) doses 21 days apart and the Moderna vaccine is administered as 100μg/0.5mL (200 μg/mL) doses 28 days apart. Assuming similar sized constructs, this means that each mRNA-1273 dose provides three times more mRNA copies of the Spike protein than BNT162b2, which could result in more effective priming of the immune response.

https://www.medrxiv.org/content/10.1101/2021.08.06.21261707v1.full-text (Discussion section)

The interval might also be relevant: a slightly longer interval can lead to more of a boosting effect from the second dose, based on what they have seen in countries that stretched to get more first doses out.

This preprint does need a bit of cleanup, though. It is mentioned elsewhere, but they forgot to list age in the "Defining matched cohorts of vaccinated and unvaccinated individuals" section under Methods.

I think in a perfect world they also would match by community or Zip code because distribution of the two vaccines may not have been geographically random.