The advantage of the RNA vax is their simplicity. They encode only the spike protein because it's the viral protein targeted by most of the antibodies that prevent viral entry. Another way to put it is Abs to the right place on spike are sufficient to block entry. (image Siemens)
The adenovirus vax also encode only spike but express it from Ad. Both types elicit high levels of neutralizing antibodies (nAbs) after just one dose. RNA is better here; in fact 1 dose of RNA gives you similar nAb levels to natural infection.
But immunizing just to spike limits the nAb repertoire. There are only a few places where Abs tend to bind to spike, and it seems binding to a loop containing E484 actually accounts for much neutralizing activity, as E484K drops neutralizing activity 3x.
The delta variant has both E484K to give that 3x lower neutralization, and another mutation P681R that is believed to enhance membrane fusion and thus the rate of viral entry. Overall neutralization activity of antisera is down ~6x (today's Lancet paper)
A landmark paper in May related nAb levels to % efficacy in trials (in terms of % protection from symptomatic disease). Using their efficacy-vs-nAb curve, and with Ab levels at 3x of convalescent sera, the 6x drop in nAb potency predicts efficacy at ~70%. doi.org/10.1038/s41591…
The Chile study I posted above measured nAb levels post-Pfizer/BioNTech at 10x convalescent sera, so it's not clear if 3x or 10x is more common. If 10x, then efficacy would be predicted to remain >85% even with a 6-fold loss of potency against the delta strain.
And now this is rather preliminary and verification is required, but an April preprint reported that nAbs elicited by Covaxin, the whole-killed/inactivated virus vaccine, showed only a 2x dropoff in potency against delta.
That's potentially interesting because whole killed/inactivated virus vaccines present the entire virus. In addition to spike, there are two other surface proteins, E and M. Anti-spike is certainly sufficient for neutralization, but perhaps anti-E and anti-S can contribute too.
So, to wildly speculate: in whole-virus vaccines, maybe you get a mix of the anti-spike (predominantly anti-E484), anti-E, and anti-M. Then if you lose the spike binding with E484K, you still get some neutralizing activity through E and M. Requires more study to know for sure.
The other thing that whole-virus vaccines present are the intracellular viral antigens. Dendritic cells (DCs) route some phagocytosed antigens to MHC-I via cross-presentation, so they can activate CD8 T cells with TCRs that recognize those viral antigens. en.wikipedia.org/wiki/Cross-pre…
Intracellular viral antigens presented on MHC-I by infected cells then induce killing by these activated cytotoxic CD8+ T cells (CTLs). Dogma is that DC cross-presentation is not reliable enough as a vaccine mechanism, but this is not always true. journals.asm.org/doi/full/10.11…
Now whole-virus vaccines such as Coronavac, Sinovac, and Covaxin do seem to have very little activity after the first dose, in contrast to RNA and Ad vaccines. Immune activation is just not as strong with dead virus and adjuvant as RNA or Ad.
However after dose 2, the whole-virus vax appear similar to convalescent sera. If they can maintain 50% neutralizing potency on new variants, then after dose 2, they will still be able to prevent symptoms by >50% and severe cases by >80%.
Adding a correction to main thread: Delta/B.1.617.2 has T478K; Kappa/B.1.617.1 has E484K.
They are on the same loop and both resist neutralizaing antibodies elicited to wild-type spike, so analyses and implications are unchanged.
Also the 2x hit on Covaxin-elicited neutralization mentioned above was with Kappa/B.1.617.1. So for comparison we should look at RNA vaccine-elicited nAbs to B.1.617.1. They are down 7x.
We don't know Covaxin result on B.1.617.2; will be important to get
To add a little background, anti-M antibodies are seen after coronavirus infections. Anti-E antibodies have not been seen so far. nature.com/articles/s4146…
Meant "perhaps anti-E and anti-M can contribute too." Some evidence for anti-M.
In trials the Pfizer/BioNTech vax was estimated to be 88% effective against Delta in UK. That's very good news, and suggests the vax elicits very high nAb levels and/or T cell responses so that the 6x drop in nAb potency is not hindering efficacy too much
3a is another coronavirus transmembrane protein that, in SARSCoV1, was found to be targeted by neutralizing antibodies. It appears nobody has published anything on 3a of SARSCoV2 yet (S is clearly the right protein to target if you have to pick one)
Novavax beats Moderna, which (transiently) induces higher levels of neutralizing Abs. As I've said before, Abs are much more than neutralization. Ab effector functions do most of the clearing, and Novavax seems particularly good at that.
And this is in the 2-dose Phase 3 trials, before the 3rd "booster" dose that, in RNA vaccines but not Novavax, induces antibody (immunoglobulin) class-switching to the no-effector-function IgG4
I made this graphic to show how different vaccine types work (back in 2021).
We can just look at line 1 (protein vax like Novavax) and line 3 (RNA vax).
In protein vax, antigen-presenting cells take up the antigen to activate B cells and Thelper cells....
In RNA vax, your muscles cells take up RNA and translate it into antigen. This process tends to be a bit inflammatory (apparently that's inherent to RNA uptake) so some cells die and release proteins that are also taken up by antigen-presenting cells.
Basically Pelosi figured out Donilon was the one feeding Biden hopium-spiked poll results, and leaked it out.
Once it was proven that there really was bad info in the inner circle, that gave everyone else confidence in their own eyes. The emperor really was naked.
“Put Donilon on the phone,” Ms. Pelosi told the president, referring to Mike Donilon, the president’s longtime aide, according to people familiar with the exchange, which was reported earlier by CNN. “Show me what polls.”
Biden has COVID-19 again. He had first symptoms today, positive test today, and first Paxlovid dose today.
As the early Paxlovid will limit immunostimulation by virus, I predict he will suffer rebound again, unless he gets 10-day course, or he is given a strain-matched vaccine.
Biden's DO does not seem to follow the science. The rate of rebound is 26% if started within the first 2 days of symptoms or positive test.
Sure, FDA and CDC and Pfizer still claim it's less than 3% and no different than no-Paxlovid, but it fools nobody
I predicted his first rebound on immunological principles alone and on understanding Paxlovid mechanism of action. It was a real prediction, made before it happened, and sticking my neck out in public to make it.
I intuited that early start of Paxlovid blunts immunity, allowing viral rebound once drug ended. I thus predicted both Joe and Jill Biden's rebounds (before they occurred), as they started Pax on day of symptoms.
"The model identifies that earlier initiation and shorter treatment duration are key predictors of post-treatment rebound."
The model shows that early therapy reduces the number of infected cells secreting innate immune signals (IFNs) that then activate antibody production.
"If the virus is not eliminated by an early acquired response along with antiviral pressure, it rebounds to a peak level that is sometimes comparable to the initial peak."
We have seen this with many people, e.g. Fauci reported the rebound was worse than the initial infection