[mumblemumble]

According to FDA, phase III trials typically take 1-4 years.

It's worth noting that, if there are any adverse effects that take a while to become apparent, the trial will need at least that long to be able to detect them. To my knowledge, severe vaccine reactions usually happen fairly soon, but a year before onset isn't necessarily unheard of for some vaccines. Also, that's just for vaccines that got approved; there may be some selection effects there.

The bigger one I'm worried about is whether or not the vaccine will confer lasting immunity. If we rush a vaccine to market in six months, everybody gets it, and returns to their pre-pandemic lifestyles, then we'll be in for a nasty surprise on down the road if it turns out that it only confers immunity for a year. It seems to me like we need to consider the possibility that an imperfect vaccine is worse than no vaccine at all.

[RangerScience]

If the vaccine only confers a few months of immunity, like the yearly flu vaccine, how long does it take to develop, produce and distribute the update?

[aphextron]

>If the vaccine only confers a few months of immunity, like the yearly flu vaccine, how long does it take to develop, produce and distribute the update?

The Pfizer and Moderna vaccines are mRNA based, which means the iteration time is measured in weeks. The production process is massively simplified; it's just a chemical process like any other drug, rather than needing to be incubated in chicken eggs like a flu vaccine. The first mRNA vaccines for SARS-CoV-2 were being administered within 2 months of the outbreak. If these things work (and they do; phase 2 trials have shown immunogenicity 3-4 times higher than COVID convalescent plasma [0]), and they are proven to be safe in widespread usage, it will potentially revolutionize vaccine development. COVID could end up saving lives in the long run for the fact that it sped up the timeline on mRNA vaccines by a decade.

[0] https://www.medrxiv.org/content/10.1101/2020.08.17.20176651v...

[CydeWeys]

Good news is that COVID (and coronaviruses in general) don't seem to have the same kind of mutation potential to bypass immune system responses like influenza does. So our best guess is that a COVID vaccine will be like Tdap or MMR, i.e. after the initial course you maybe only need occasional booster shots (if even that), vs influenza where it mutates enough that a new vaccine must be developed and administered every year.

[Gibbon1]

Not widely enough understood. Influenza is a segmented virus and generates new strains by reassorment. Where two different strains of influenza infecting a cell shuffle their RNA segments to produce a third strain.

Best to think of influenza as an ever shifting and recombining family of viruses.

Covid19 has a single strand of RNA and doesn't do that.

[hartator]

I think the yearly flu vaccine give you lifetime immunity against the strains you are vaccinated against. However flu strains change every year. (Hopefully that won’t be the case for covid!)

[mumblemumble]

Officially, it gives you at least 6 months' worth of immunity, but, beyond that, there are no guarantees, and it generally fades over time.

That's why the recommendation is to wait until shortly before the onset of flu season to get vaccinated: If you get vaccinated in July, there's no guarantee that the vaccination will carry you through the worst of a (northern hemisphere) flu season.