The flu vaccine works.
How well does it work?
It depends…
How Effective Is the Flu Vaccine?
What does it depend on?
“The vaccine effectiveness of seasonal influenza vaccines is a measure of how well the seasonal influenza vaccine prevents influenza virus infection in the general population during a given influenza season.”
WHO on Vaccine effectiveness estimates for seasonal influenza vaccines
Is the flu virus that is going around the same strain that was picked to be in the flu vaccine?
Has the flu virus drifted, even if it is the same strain that is in the flu vaccine, becoming different enough that your protective flu antibodies won’t recognize it?
Is the H3N2 strain of flu virus the predominate strain during the flu season? H3N2 predominant flu seasons are thought to be worse than others.
In general, the flu vaccine is going to be less effective in a season where there is a poor match between the circulating strain of flu virus that is getting people sick and the strain that is in the flu vaccine, especially if it is an H3N2 strain that has drifted.
That’s why, since the 2004-05 season, the average flu vaccine effectiveness has been about 41%.
How Effective Is This Year’s Flu Vaccine?
It’s probably also why, every year, we seem to hear the same questions:
- Should I get a flu vaccine? – yes, definitely
- Will we have enough flu vaccines? – while historically there have been some delays and shortages, we have a very good supply of flu vaccine this year, between 151 to 166 million doses
- How effective is this year’s flu vaccine???
Unfortunately, we usually don’t know the answer to that last question until this year’s flu season really gets going.
In recent years though, the flu vaccine has been working fairly well though.
While certainly not at the very high efficacy levels that we expect from other vaccines, like measles (95 to 99% efficacy), but not at the very low 10% efficacy that folks who are against vaccines like to throw out.
The Flu Vaccine Works
It is also important to remember that getting a flu vaccine has many benefits, few risks, and can:
- reduce your chances of getting the flu
- reduce the chances that your newborn gets the flu if you get your flu shot while pregnant
- lead to milder symptoms if you do get the flu
- reduce your risk of being hospitalized
- reduce your risk of dying from the flu
And while it isn’t perfect, getting a flu vaccine is certainly better than remaining unprotected and simply taking your chances that you won’t get the flu and complications from the flu.
What to Know About Flu Vaccine Effectiveness
Although the effectiveness of the flu vaccine varies from year to year, depending on how well matched the vaccine is to circulating flu virus strains, which strains are dominant, and whether they have drifted, it is always a good idea to get vaccinated and protected.
More on the Effectiveness of Flu Vaccines
- Is This Year’s Flu Shot Only 9% Effective?
- Is This Year’s Flu Vaccine Working?
- Why Do You Need to Get a Flu Vaccine Each Year?
- Do They Really Just Guess at Which Strain to Put in the Flu Vaccine?
- Can I Get a Second Flu Shot for Extra Protection?
- Will This Season’s Flu Shot Fail?
- CDC – Past Seasons Vaccine Effectiveness Estimates
- CDC – US Flu VE Data for 2019-2020
- CDC – Vaccine Effectiveness: How Well Do the Flu Vaccines Work?
- CDC – How Flu Vaccine Effectiveness and Efficacy are Measured
- CDC – Why CDC Estimates Vaccine Effectiveness (VE)
- 2017 flu vaccine effectiveness – getting the facts straight
- Flu Vaccine Benefits Go Beyond Effectiveness of One Strain
- Why Get A Flu Shot?
- Ask the Experts about the Flu Vaccine
- Study – Effectiveness of inactivated influenza vaccines varied substantially with antigenic match from the 2004-2005 season to the 2006-2007 season.
- Study – Influenza vaccine effectiveness against hospitalisation with influenza in adults in Australia in 2014.
- Study – 2014–2015 Influenza Vaccine Effectiveness in the United States by Vaccine Type
- CDC – Interim Estimates of 2016–17 Seasonal Influenza Vaccine Effectiveness — United States, February 2017
- Study – Chasing Seasonal Influenza — The Need for a Universal Influenza Vaccine
- WHO – Vaccine effectiveness estimates for seasonal influenza vaccines
- No, the CDC did not just “admit” that this year’s flu vaccine doesn’t work
- Flu vaccine research and development – eggs cause low effectiveness
- If I Had Gotten the Flu Shot