Older adults face a double whammy: their immune systems don’t bounce back like they used to, and the flu can knock them down harder than younger folks. That’s why vaccines are so critical. But there’s been a nagging question: if you’re one of the millions of older adults popping a daily low-dose aspirin for your heart, does it make your flu shot less effective?

Why the concern?

  • Inflammation is part of how vaccines teach your immune system to fight.
  • Painkillers like acetaminophen (Tylenol) and NSAIDs (ibuprofen, aspirin) tamp down inflammation.
  • One study even showed that giving Tylenol to babies after vaccines blunted their antibody response.

So the theory was: if aspirin dulls inflammation, maybe it blunts your immune system’s response to the flu vaccine, too. And since up to 70% of seniors get vaccinated and many take aspirin daily, this could be a big deal.

The study

Researchers pooled data from four major clinical trials of the 2009 H1N1 flu vaccine. They looked at nearly 1,600 adults aged 50+, about 43% of whom were regular aspirin users. Then they compared antibody levels 3 weeks after vaccination.

The results

  • Antibody levels in aspirin users? About the same as non-users.
  • After adjusting for age, health conditions, and medications, aspirin users were not less protected.
  • In fact, if anything, their antibody levels were slightly higher—but the difference wasn’t statistically meaningful.

Why this matters

  • Reassuring news: if you’re taking daily aspirin for heart health, your flu shot should still work.
  • Big contrast to kids: the effect seen with Tylenol in infants doesn’t seem to carry over to older adults.
  • Practical takeaway: don’t ditch your aspirin just because it’s flu season.

The fine print

  • The study looked only at the H1N1 vaccine, not the seasonal flu shot or other vaccines.
  • People self-reported their aspirin use, which isn’t perfect.
  • Other NSAIDs (ibuprofen, naproxen) weren’t specifically tested here.

Bottom line

Daily aspirin doesn’t blunt your flu shot. So if you’re over 50 and taking aspirin for your heart, you can roll up your sleeve with confidence. Your immune system’s got this one covered.

Jackson ML, Bellamy A, Wolff M, Hill H, Jackson LA. Low-dose aspirin use does not diminish the immune response to monovalent H1N1 influenza vaccine in older adults. Epidemiol Infect. 2016 Mar;144(4):768-71. doi: 10.1017/S0950268815002058. Epub 2015 Sep 2. PMID: 26330204; PMCID: PMC4737981.