We've posted a bit (here and here) on this year's flu vaccine and some mismatches. Because of the time it takes to ramp up production the flu vaccines for the following season are made in the early spring of the year before, often, as now at the peak of the ongoing flu season. Yesterday WHO announced that they were changing all three of the strains in next year's vaccine, something that is unusual but not unprecedented.
This is all reported by the best of the best flu reporters, Canadian Press's Helen Branswell. I could do some pull quotes and summarize what she wrote, but instead I'll just send you there. I can't improve on her version. Go there and read it. It is so well done that it just makes you shake your head in admiration. It isn't flashy or stylish. It appears effortless and her voice is unobtrusive but I'm guessing a lot of hard work went into it. It is just plain superior reporting.
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Revere-They make reference to the H3N2 virus growing poorly. Is that a back door way of saying that it killed the eggs or was there some other mechanism at work that kept it from growing? As I understand it they inject it into those high tech chicken eggs, then they let it grow for a week or two and then siphon the interior of the eggs out and then separate it?
You are right about H.B. Good article. I didnt take it this year for reasons previously given. Seems like it didnt work so hot and everyone I know got sick. If I was still in the military I would be likely down and hard from the vaccine.
Fickle flu-tations.
Randy: I don't know what the growth problem was. It sounds like for some reason they couldn't harvest enough virus for the eggs inoculated but I don't know the reason.
> We're trying to forecast what's going to be circulating almost a year from now. . . .
> (But) influenza has demonstrated that to us time and time again, that it's impossible
> to predict with certainty what's going to be circulating a year from now."
> Still, often those predictions are good.
"predict with certainty" ?
when you are certain, it's no longer called prediction but prophecy or foretelling.
Of course, certainety comes in degrees, so let's replace "certain" above
with 99% certain.
"impossible to predict with certainty", I interpret it that considering all
available data a bet with quote 1:99 or worse would be unreasonable.
"predictions are good" , I interpret it: what we actually saw often
(>70%) was the predicted strain, produced in the chosen vaccine.
these are just the usual games to create ever more phantasyfull
words in orrder to say something without being clear and
avoiding the clearer use of numbers for subjective probabilities.
Helen Branswell is no exception here, sigh.
why is it better for vaccine producers
to use old strains ?
Is it cheaper ? How much ?
We could produce six-valent vaccine if we wanted,
just a matter of money.
1,2,3,4,5,6 - valent, what's the most reasonable choice ?
Unlikely that it's the same each year.
So why aren't they more flexible ?
re: the poor growth of H3N2 viruses in eggs - this is not due to human H3N2 viruses killing the eggs. Viruses that grow well in eggs usually bind well to alpha2-3 linked sialic acids (the avian preference). However, recent H3N2 viruses bind to alpha2-6 linked sialic acids (the human preference). Modern H3N2 isolates possess changes in their HA receptor binding site that limit their ability to grow to high titers in embryonated eggs.
Well, so much for it shaping up to be an H1 year. Today's update shows H3 pulling strongly into the lead, with all but five states at "widespread" status. Where I live (California) we never made widespread at all last year. Any bets on how much longer we can expect to see sensitivity to neuraminidase inhibitors in the H3 strains?
racter: As I recall the same thing happened last year. H3 is ramping up and with it a lot of flu in the community. I saw the same CDC report and may post on it.
Racter-Wasnt it H3 two and three years ago? If it was then it stands to reason you wouldnt get that strain the third year. I distinctly remember seeing an article about how all the emergency rooms were loaded with patients packing H3. If you didnt have it going into the ER, you had it when you came out because of the waiting time.
Randy: H3 isn't a strain. It is a subtype. H1 and H3 have been circulating simultaneously, in different proportions each year. They each change strains periodically.