Does the flu shot work less well as you get older?
The flu shot demonstrably works less well in older adults than in younger people, but high-dose and other improved vaccines substantially reduce that disadvantage. Ask your doctor or pharmacist whether you qualify for such an improved vaccine.
The flu shot is effective in roughly 31% of cases among older adults aged 65 and above. In children under 18 that figure is nearly 49%, and in adults between 18 and 64 it is 37%. This difference has been confirmed in a large analysis of 191 studies and has been demonstrated with statistical confidence.
Two biological mechanisms explain this pattern. First, the immune system ages: it responds more slowly and less powerfully to a vaccine. Second, the immune systems of older adults rely heavily on memories of past flu infections, making it harder for them to respond to new variants of the virus. Both effects reinforce each other. In addition, the standard vaccine already protects everyone less well against the A/H3N2 strain of the flu virus (26.8%) than against other strains (up to 55%), which puts older adults at an additional disadvantage given that they are already starting from a more vulnerable position.
Fortunately, there are alternatives to the standard vaccine that work noticeably better in older adults. A high-dose vaccine, containing four times as much active ingredient as the regular version, led over ten flu seasons and in more than 22 million people to 16% fewer flu-like illnesses, nearly 12% fewer hospital admissions due to flu, and more than 27% fewer pneumonia-related admissions compared with the standard vaccine. Deaths from flu or pneumonia were even 40% lower. A vaccine containing an immune-boosting additive (adjuvant) showed 25% fewer hospital admissions compared with the regular vaccine in observational studies. A so-called recombinant vaccine also performs better. Which of these three types scores best cannot be determined on the basis of current studies: they are close to one another.
Whether getting the shot every year further reduces your protection is still unclear. Some studies see a slightly diminishing effect in people who are vaccinated every year, while other studies do not. Sufficient long-term research for a clear conclusion is still lacking here.
Based on a meta-analysis of 191 studies (PMID 38423813), a large data analysis covering more than 22 million people and 10 seasons (PMID 33422382, 32515178), an observational study on MF59-adjuvant vaccines (PMID 28024956), a systematic review on improved vaccines (PMID 39230284), and mechanistic reviews (PMID 33650528, 32515178). The evidence on repeated vaccination is insufficient (PMID 34857422).
Why are older adults more susceptible to influenza?
Older adults are more susceptible to influenza due to a combination of an ageing immune system, chronic diseases, and low-grade background inflammation. Ask your doctor or pharmacist whether, as someone aged 65 or over, you can receive a high-dose influenza vaccine, as it offers better protection than the standard formulation.
Does your immune system really weaken as you get older, and can you do anything about it?
Your immune system demonstrably weakens with age, but eating healthily and exercising can reduce the smouldering inflammation that accompanies it. It is still too early to rely on drugs targeting senescent cells.
Does your immune system really weaken as you get older?
Your immune system does indeed weaken as you get older, but how quickly that happens varies considerably from person to person. Lifestyle factors play a role in this, although little has yet been proven specifically for humans.
Does spending more time outdoors help your immune system as you get older?
Spending more time outdoors may support your immune system as you get older, mainly through improved vitamin D production, but whether this actually leads to less illness has not yet been conclusively demonstrated. How polluted the outdoor air is also matters: in areas with serious air pollution, being outside can in fact be detrimental.
Why do older adults become seriously ill from an infection more quickly?
Ageing weakens the immune system in several ways simultaneously, making infections more dangerous. Keep vaccinations up to date and discuss nutritional deficiencies with your doctor, as these additionally increase vulnerability.
Does exercise help your immune system as you age?
Regular, moderate exercise helps your immune system by reducing smouldering inflammation. Suddenly training very hard without a gradual build-up can actually temporarily lower your immune defences.