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Originally Posted by calgarygeologist
Question for anyone that knows about vaccines either by education or just by significant research recently because I don't feel as though I understand things very well. Does it seems like the effectiveness provided by mRNA vaccine (ie the covid vaccine) is disappointing? There are reports out today that apparently a third dose, booster, loses effectiveness as early as 4 months and this is on the heels of the second dose losing effectiveness after 6 months. Maybe this is just because of the Omicron variant and if we were still dealing with earlier variants the effectiveness would not drop off as quickly but I really don't know.
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Coronavirus antibodies wane; there's not much we can do about that. However, the reason the effectiveness is waning so quickly is entirely because of Omicron. Antibodies to prior variants can neutralize Omicron, but it's more through brute force so you need a lot of them. So where a 3rd dose could conceivably give very good protection against Alpha or Delta for perhaps a year or so, it's only a few months for Omicron because the antibodies are far less suited to neutralizing it. That is to say, after 4 months you might have an antibody response to Delta that's 10x what's needed for neutralization, but not enough of a response against Omicron to neutralize it.
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If we had a "conventional" live vaccine instead of mRNA would we be in a better position hypothetically? The biggest benefit of mRNA vaccine is the increased speed of development and production but are we sacrificing protection for that speed?
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Likely not. Inactivated COVID vaccines exist and they're generally not very good at all compared to the better alternatives (though they are much better tolerated). There aren't any live attenuated virus vaccines in use yet, but there is an intranasal one being studied, though there isn't any reason to think it would be inherently more effective. Antibody responses to the non-spike parts of the virus are either more or less useless at neutralization (in the case of the N-protein) and/or only visible to the immune system after infection (the envelope and membrane proteins), so they're not going to help too much by being in a vaccine. There's a reason the spike protein was chosen by virtually every vaccine maker as the target.
And it's not like mRNA are the only ones in use. There are also viral vector (AZ and J&J) as well as recombinant protein (Novavax) vaccines. That's not to say there's no improving on the current vaccines; 2nd generation ones might provide longer-lasting or better protection that's more resistant to variants; or they might have far fewer adverse reactions, but there are going to limits to what's capable with a coronavirus vaccine.