Question explored with the scientific record
Is it still worth taking the Flu vaccine at age 65+
For someone 65 or older, the flu vaccine shows a consistent association with lower all-cause mortality across many studies, but the size of that benefit is modest and the evidence is almost entirely observational, not from blinded trials.
The studies retrieved all compare people who chose to get vaccinated against people who did not. That is a fundamental limitation. People who get the flu shot are systematically healthier, wealthier, and more engaged with medical care than people who skip it. This "healthy user bias" can easily produce the appearance of a large mortality benefit that has nothing to do with the vaccine itself. One study of elderly South Africans directly tested this: after adjustment, the vaccine looked beneficial, but sensitivity analysis showed that unmeasured healthy-user bias could explain the entire finding. The authors called the data inconclusive [5].
Several other observational studies report mortality reductions ranging from about 10% to nearly 50% [1][2][3][8][9][10]. But the better the study controls for bias, the smaller the benefit. A 2009 analysis of 115,000 Kaiser Permanente members found the vaccine reduced mortality by only 4.6% during flu season [6]. The difference between a 50% claim and a 5% claim is the difference between poorly controlled bias and well-controlled bias. The most credible estimate from the retrieved evidence is that the vaccine lowers all-cause mortality in the elderly by something like 5–10% during a season with a good match, not the dramatic figures often quoted.
There is some evidence that newer formulations (adjuvanted or high-dose) may work slightly better in the elderly than the standard shot. One cluster trial found the adjuvanted vaccine reduced all-cause hospitalization by 6% and pneumonia-or-influenza hospitalization by 21% compared to the standard dose [7]. But that trial was funded by the manufacturer, Seqirus, and the absolute benefit was still small.
| Population and comparison | All-cause mortality reduction | Notes |
|---|---|---|
| Community elderly, bias-adjusted meta-analysis [3] | OR 0.64 (36% reduction) | Bias adjustment reduced I² heterogeneity to near zero for this estimate |
| Kaiser Permanente elderly, well-adjusted [6] | 4.6% relative reduction | Much smaller than unadjusted studies; more credible |
| Diabetic elderly, pooled meta-analysis [2] | OR 0.54 (46% reduction) | Very high heterogeneity (I² = 96%); almost certainly inflated by bias |
| Nursing home residents, staff vaccination [4] | 5 fewer deaths per 100 residents | From a randomized trial of staff vaccination; indirect benefit to residents |
The vaccine is cheap, low-risk for serious harm, and the modest mortality reduction appears real — but it is far smaller than advocacy materials suggest. Seasonal effectiveness also varies wildly depending on whether the circulating flu strain matches the vaccine.
My call: flu vaccination at age 65+ is probably worth it if you want a small probable mortality reduction each season, but the average benefit is around a 5% relative drop in all-cause deaths, not the 50% that many studies claim. You are not wrong to skip it, especially in seasons where the match is poor. Confidence: moderate — the direction is consistent across studies, but the true size is uncertain because the entire evidence base is observational.
Sources used 10
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Impact of influenza vaccination on GP-diagnosed COVID-19 and all-cause mortality: a Dutch cohort study
In a Dutch primary-care cohort of 223,580 adults, influenza vaccination in 2019 was associated with slightly higher GP-diagnosed COVID-19 rates (HR 1.15; 95% CI 1.08 to 1.22) but slightly lower all-cause mortality (HR 0.90; 95% CI 0.83 to 0.97).
DOI: 10.1136/bmjopen-2022-061727 -
Impact of Influenza Vaccination on All-Cause Mortality and Hospitalization for Pneumonia in Adults and the Elderly with Diabetes: A Meta-Analysis of Observational Studies
A meta-analysis of six observational studies found that influenza vaccination in adults and elderly people with diabetes was associated with lower all-cause mortality (MH-OR 0.54, 95% CI 0.40-0.74) and lower hospitalization for pneumonia (MH-OR 0.89, 95% CI 0.80-0.98).
DOI: 10.3390/vaccines8020263 -
After adjusting for bias in meta-analysis seasonal influenza vaccine remains effective in community-dwelling elderly
A methodological meta-analysis comparing conventional and bias-adjusted approaches to estimating seasonal influenza vaccine effectiveness in community-dwelling elderly, showing that bias adjustment reduces heterogeneity and yields significant protection against hospitalization f…
DOI: 10.1016/j.jclinepi.2014.02.009 -
Effectiveness of an influenza vaccine programme for care home staff to prevent death, morbidity, and health service use among residents: cluster randomised controlled trial
A cluster-randomised trial in UK care homes found that vaccinating care home staff against influenza reduced resident mortality, influenza-like illness, GP consultations for influenza-like illness, and hospital admissions during periods of influenza activity in the 2003-04 seaso…
DOI: 10.1136/bmj.39010.581354.55 -
Effectiveness of influenza vaccination in the elderly in South Africa
In a nested case-control study of medically insured elderly in South Africa, influenza vaccination was associated with fewer serious complications after full adjustment, but sensitivity analysis suggested healthy-user bias could explain the findings, so the data were inconclusiv…
DOI: 10.1017/s0950268808001386 -
Influenza Vaccination and Mortality: Differentiating Vaccine Effects From Bias
This study investigates the impact of influenza vaccination on mortality among elderly members of Kaiser Permanente in Northern California, revealing a vaccine effectiveness of 4.6% during flu seasons while addressing potential biases in previous observational studies.
DOI: 10.1093/aje/kwp173 -
An overview of new data on the relative effectiveness of flu vaccines in vulnerable populations
Adjuvanted influenza vaccine in elderly nursing-home residents reduced all-cause hospitalizations by 6% and pneumonia-or-influenza hospitalizations by 21% compared with standard-dose vaccine, with no difference in respiratory-related hospitalizations.
DOI: 10.70270/5tq0xqx -
Effects of previous influenza vaccination on subsequent readmission and mortality in elderly patients hospitalized with pneumonia
An observational, retrospective cohort study of 12,566 elderly Medicare beneficiaries hospitalized with pneumonia, finding that influenza vaccination before hospitalization is associated with lower subsequent mortality and hospital readmission compared with unknown vaccination s…
DOI: 10.1016/s0002-9343(03)00440-6 -
The Health and Economic Benefits of Influenza Vaccination for Healthy and At-Risk Persons Aged 65 to 74 Years
This study assesses the health and economic benefits of influenza vaccination for healthy and at-risk seniors aged 65 to 74 years, finding that vaccination is associated with significant reductions in hospitalizations and mortality, and is cost-saving.
DOI: 10.2165/00019053-199916001-00009 -
Influenza Vaccine Effectiveness in Preventing Hospitalizations and Deaths in Persons 65 Years or Older in Minnesota, New York, and Oregon: Data from 3 Health Plans
This study assesses the effectiveness of influenza vaccination in reducing hospitalizations and deaths among elderly individuals aged 65 and older across three health plans in Minnesota, New York, and Oregon, finding significant reductions in both outcomes during two influenza s…
DOI: 10.1086/323085