"The study will evaluate up to 1,420 participants across the three cohorts:
"Cohort #1 (n = 615): Received two doses of the current Pfizer-BioNTech COVID-19 vaccine 90-180 days prior to enrollment; in the study, participants will receive one or two doses of the Omicron-based vaccine
"Cohort #2 (n = 600): Received three doses of the current Pfizer-BioNTech COVID-19 vaccine 90-180 days prior to enrollment; in the study, participants will receive one dose of the current Pfizer-BioNTech COVID-19 vaccine or the Omicron-based vaccine
"Cohort #3 (n=205): Vaccine-naïve participants will receive three doses of the Omicron-based vaccine"
Thanks for sharing this. Did you notice how they describe the trial? "Safety, tolerability, and immunogenicity." They didn't say "efficacy." Back when you and I first discussed the possibility of a variant-specific vaccine, we talked about whether they would just look at immunogenicity, as they do for influenza vaccines, to avoid the need for expensive and time-consuming efficacy analyses. It looks like that's what they're doing!
And that seems justified, since it appears primarily that Omicron evades immunity rather than being very different in terms of its inherent transmissibility.
I realize that we are dealing with different strains and that coronaviruses never generated much permanent immunity, but the idea that an actual viral infection does not result in immunity as (or more) effective as a vaccine goes against my clinical expectations. I thought that reinfection rates have remained fairly low despite shifts in SARS-CoV-2 strains. Is it possible that, when we study vaccine effectiveness, we are measuring immunity to Delta or Omicron in a fairly specific or limited way, thus missing other ways in which an actual infection might generate immunity? Should we perhaps be calling it "measurable Omicron immunity" instead?
I think we should absolutely be making this distinction. I believe what we have been seeing primarily in Omicron vs prior variants is immune evasion, not immune waning.
I do believe it is clear that there is some waning of immunity among recovered persons, and perhaps also some among vaccinated persons (I am less convinced of this in the latter case, because I haven't seen studies wherein over time, vaccinated people became more susceptible to the WHN-01 variant--only increased susceptibility to variants that escaped immunity to varying degrees). We did see, to some extent at least, reinfection of recovered persons with the same variants that they initially got, back in 2020. So in those cases I think there is a clear case for waning taking place.
I think the word "waning" has been misapplied in the pandemic to situations that represent immune escape. Omicron is clearly a variant that evades preexisting immunity to other variants, to at least some degree.
Pfizer just announced that they're starting their Omicron vaccine trial: https://investors.pfizer.com/Investors/News/news-details/2022/Pfizer-and-BioNTech-Initiate-Study-to-Evaluate-Omicron-Based-COVID-19-Vaccine-in-Adults-18-to-55-Years-of-Age/default.aspx. From the press release:
"The study will evaluate up to 1,420 participants across the three cohorts:
"Cohort #1 (n = 615): Received two doses of the current Pfizer-BioNTech COVID-19 vaccine 90-180 days prior to enrollment; in the study, participants will receive one or two doses of the Omicron-based vaccine
"Cohort #2 (n = 600): Received three doses of the current Pfizer-BioNTech COVID-19 vaccine 90-180 days prior to enrollment; in the study, participants will receive one dose of the current Pfizer-BioNTech COVID-19 vaccine or the Omicron-based vaccine
"Cohort #3 (n=205): Vaccine-naïve participants will receive three doses of the Omicron-based vaccine"
Thanks for sharing this. Did you notice how they describe the trial? "Safety, tolerability, and immunogenicity." They didn't say "efficacy." Back when you and I first discussed the possibility of a variant-specific vaccine, we talked about whether they would just look at immunogenicity, as they do for influenza vaccines, to avoid the need for expensive and time-consuming efficacy analyses. It looks like that's what they're doing!
And that seems justified, since it appears primarily that Omicron evades immunity rather than being very different in terms of its inherent transmissibility.
I realize that we are dealing with different strains and that coronaviruses never generated much permanent immunity, but the idea that an actual viral infection does not result in immunity as (or more) effective as a vaccine goes against my clinical expectations. I thought that reinfection rates have remained fairly low despite shifts in SARS-CoV-2 strains. Is it possible that, when we study vaccine effectiveness, we are measuring immunity to Delta or Omicron in a fairly specific or limited way, thus missing other ways in which an actual infection might generate immunity? Should we perhaps be calling it "measurable Omicron immunity" instead?
I think we should absolutely be making this distinction. I believe what we have been seeing primarily in Omicron vs prior variants is immune evasion, not immune waning.
I do believe it is clear that there is some waning of immunity among recovered persons, and perhaps also some among vaccinated persons (I am less convinced of this in the latter case, because I haven't seen studies wherein over time, vaccinated people became more susceptible to the WHN-01 variant--only increased susceptibility to variants that escaped immunity to varying degrees). We did see, to some extent at least, reinfection of recovered persons with the same variants that they initially got, back in 2020. So in those cases I think there is a clear case for waning taking place.
I think the word "waning" has been misapplied in the pandemic to situations that represent immune escape. Omicron is clearly a variant that evades preexisting immunity to other variants, to at least some degree.