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Is there an ideal time to be vaccinated against flu?

Note: I’m reposting this Q&A from September 2020 (with some 2021 updates) as a friendly reminder to get your flu shot! While this post focuses on adult flu vaccination timing, if you want to hear about kids too, just let me know and I’ll post on that later this week or next. 

Question: I remember hearing that there’s an ideal time to be vaccinated against the flu, and that vaccination too early can be a problem for later in the flu season. Is that true? Is there an ideal time to be vaccinated?

Answer: Thanks for asking, and everyone, please go get your flu vaccination! Don’t delay, do it today!  If there is an optimal time for adults to get their flu shot (in the US), it is right now (September) through the end of October, and ideally before November.  And you can get vaccinated in so many places — your local drug store, walk-in clinic, grocery store pharmacy, your primary care provider, even many workplaces offer flu shots. Now that you’ve read through my public service announcement, here’s the scoop on the timing question:

  • Flu vaccination at any time is better than no vaccination. As CDC states, “everyone ages 6 months and older should get a flu vaccine every [flu] season with rare exceptions.”
  • Evidence has been accumulating over the last decade indicating that influenza vaccine effectiveness diminishes more rapidly than anticipated. This means that adults who get vaccinated early (like in July) could be at risk much later in the flu season and at peak flu season (generally January/February). As stated in this year’s Influenza Recommendations published in CDC’s MMWR, “For nonpregnant adults, early vaccination (i.e., in July and August) should be avoided unless there is concern that later vaccination might not be possible.”
  • Some researchers working in this space suggest that the optimal flu vaccination time for most people is September/October. On the flip side, as stated in this year’s Influenza Recommendations, “Variable data concerning presence and rate of waning immunity after influenza vaccination, coupled with the unpredictable timing of the influenza season each year, prevent determination of an optimal time to vaccinate.” 
  • All that said, CDC recommends getting vaccinated before flu viruses begin spreading in your community.

Again, please go get your flu shot! We want to avoid the double burden of COVID-19 + Influenza and we can help protect ourselves and our community against influenza by getting our yearly vaccination. All our other public health prevention activities — mask wearing, social distancing, hand washing, etc. — will also help protect us against influenza, so keep at it!