How long do flu shots last? – Those nerdy girls

In general, you can expect six months of effective protection starting two weeks after your annual flu shot. In older adults, protection may wear off earlier.

Flu activity is increasing right now…it’s still a GREAT time to get your flu shot!

Getting vaccinated before flu season begins will ensure you have good protection when flu season begins. For most adults, your protection will last for at least six months. September to October are considered ideal, but it’s not too late! Flu season is just picking up speed. So if you haven’t had the flu vaccine yet, you can still benefit from it. Some would even say now is the perfect time.

📆 Two weeks from vaccination to full protection.

After an annual flu vaccination, it takes about two weeks for your body to build up protection against the flu. That’s why you should get vaccinated before It is recommended that flu season is currently underway. In the Northern Hemisphere, flu season typically begins in November, so it is currently recommended to get vaccinated in September to October.

📆Is it too late?

“The best time to plant a tree is 30 years ago. The second best time is now.”

You can still benefit from a flu vaccination until the end of the season. This also applies if you get the flu. This year’s vaccines cover four strains of flu, so the shot provides protection for strains that don’t make you sick.

📆 Maximum protection for 3-4 months.

After this initial two-week period, protection against influenza remains fairly high for three to four months in most people. A recent study examined flu cases from 2016 to 2019. They measured the relationship between days since vaccination and protection against flu. Protection declines by 7-9% per month for all adults. The value decreases more quickly in people over 65. The range for this age group is 10-11% per month.

📆 Still some protection after 6-8 months.

Studies of the effectiveness of the vaccine over time show that vaccination continues to provide significant benefit after 6-8 months.

However, the protection does not transfer well from year to year. This is partly because the vaccine is “wearing off.” The other factor at play is that the flu virus mutates easily and last year’s vaccine doesn’t always cover this year’s flu strains well in the first place.

Recent changes to flu vaccine recommendations aim to provide better and longer coverage for older adults.

Beginning in 2022, the CDC recommends higher dose or adjuvanted influenza vaccines for older adults when available. Studies suggest that these vaccines produce a stronger immune response in older adults and may be more effective or wear off more slowly over the course of the season. However, the real data isn’t there – we don’t really know yet whether these targeted formulations make a difference.

Many doctors recommend that older adults wait until the end of October to get the flu shot. In a typical year, flu season begins in November, peaks in December-January, and lasts until March-April. Wait until the End of the recommended window (hopefully) means an older adult will have good protection when flu season is at its worst. Unfortunately, flu season can be unpredictable! It is difficult to say when the peak will be reached.

So generally, flu vaccine protection peaks two weeks after vaccination and lasts, to a significant extent, for about five to six months. In older adults, protection wears off somewhat more quickly. How long your flu vaccine protects you depends on which strains are circulating, how well they are covered by the vaccine that year, and how old you are.

In any case, the 2024-2025 flu season is gathering pace. So if you haven’t gotten the flu vaccine yet, now is a good time!

Source: CDC Fluview Weekly Influenza Surveillance Report

Stay safe, stay healthy.

Those nerdy girls

**This post was adapted from the original by Dr. Malia Jones updated 11/12/23.

Link to original Substack post