I would argue that keeping the ancestral spike in the vaccine, at least until we have more evidence that the variants are not diverging from Omicron, may actually have been beneficial in this year's bivalent booster with regard to calling up a memory response - not just antibodies, but T cells. T cells are the ones that are responsible for preventing severe disease once one is infected (given that some virus will inevitably slip past the antibody defenses). In my opinion as an immunologist, the decision may have come from the fact that we really didn't know how well the omicron spike would protect us by itself. By including the ancestral spike, we were not only making sure that our memory responses were called up from previous vaccinations, but we were also guarding ourselves against the possibility that immune imprinting would mute an omicron-only response. Moving forward, now that so many people have experience with omicron, not just through the bivalent vaccine, but also by being infected, it does make sense to more fully shift our efforts...but I don't think annual boosting is in the cards for most people. The biggest efforts should be put towards developing a pan-corona vaccine. We can't keep chasing the tail of this virus forever.
It seems the only issue with the parenteral vaccine administration is that it can’t protect against mucosal infection which is the primary mode of transmission. It works well against early systemic infection but by that stage the virus is replicating in the body.
Systemic immunity is easier to measure in individuals. Mucosal immunity isn’t so easy to measure. Perhaps demonstration of efficacy requires epidemiological data after the safety of mucosal administration of an immunogen is demonstrated.
I would argue that keeping the ancestral spike in the vaccine, at least until we have more evidence that the variants are not diverging from Omicron, may actually have been beneficial in this year's bivalent booster with regard to calling up a memory response - not just antibodies, but T cells. T cells are the ones that are responsible for preventing severe disease once one is infected (given that some virus will inevitably slip past the antibody defenses). In my opinion as an immunologist, the decision may have come from the fact that we really didn't know how well the omicron spike would protect us by itself. By including the ancestral spike, we were not only making sure that our memory responses were called up from previous vaccinations, but we were also guarding ourselves against the possibility that immune imprinting would mute an omicron-only response. Moving forward, now that so many people have experience with omicron, not just through the bivalent vaccine, but also by being infected, it does make sense to more fully shift our efforts...but I don't think annual boosting is in the cards for most people. The biggest efforts should be put towards developing a pan-corona vaccine. We can't keep chasing the tail of this virus forever.
It seems the only issue with the parenteral vaccine administration is that it can’t protect against mucosal infection which is the primary mode of transmission. It works well against early systemic infection but by that stage the virus is replicating in the body.
Systemic immunity is easier to measure in individuals. Mucosal immunity isn’t so easy to measure. Perhaps demonstration of efficacy requires epidemiological data after the safety of mucosal administration of an immunogen is demonstrated.