Old Oct 23, 19, 6:07 pm
FlyerTalk Evangelist
Join Date: May 2002
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Very interesting question.

I'll leave it to the experts to provide actual data, but my understanding is the flu strains are constantly evolving and mutating. CDC often uses data from the Asia to predict strains that will be in the US during flu season. This would seem to imply that they get flu strains not in the US vaccination in advance. Once article says

H3N2 viruses are always going around in East and Southeast Asia, and spread to the rest of the world in yearly flu epidemics — which is how we can predict what strains are coming each year. Between worldwide epidemics, H3N2 strains die out everywhere but the west. That means each yearly epidemic spreads out from that reservoir, including the new strains you need to get a fresh shot for.
So, in theory, next year's US flu season strain (and what will be in next year's vaccination) may already be mutating and circulating in some of the places you're headed. Not sure what you can do about it though.

Here's a map showing the variety of current strains around the world. FWIW, this year's US vaccine:
  • The A(H1N1)pdm09 vaccine component was updated from an A/Michigan/45/2015 (H1N1)pdm09-like virus to an A/Brisbane/02/2018 (H1N1)pdm09-like virus.
  • The A(H3N2) vaccine component was updated from an A/Singapore/INFIMH-16-0019/2016 A(H3N2)-like virus to an A/Kansas/14/2017 (H3N2)-like virus.
  • Both B/Victoria and B/Yamagata virus components from the 2018-2019 flu vaccine remain the same for the 2019-2020 flu vaccine.
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