Question explored with the scientific record
Is it dangerous for older people tp take flu jabs
The short version: for most older adults the flu shot probably reduces your chance of a bad outcome from influenza, but the evidence is weaker than you have been told and the benefit is smaller than the marketing suggests.
The evidence here is almost entirely observational, not from randomized trials. That matters because healthy people are more likely to get vaccinated, so the studies compare people who are already healthier to people who are sicker, and that inflates the apparent benefit. One systematic review rated the overall evidence quality as low and found that heterogeneity was so high they could not even pool the results for hospitalization [25]. A bias-adjusted meta-analysis found that after correcting for the healthy-user effect, the vaccine still reduced all-cause mortality by about 36% and hospitalization for pneumonia by about 25% in community-dwelling elderly [5]. But those are the bias-adjusted numbers, and they come from observational data, not from a single large randomized trial that followed vaccinated and unvaccinated people the same way.
The disease burden is real. In China, adults 65 and older had about 123 excess deaths per 100,000 per year from all causes during influenza season [3]. In the US, community-acquired pneumonia in older adults caused more hospitalizations than heart attacks or strokes [15]. So the disease is not trivial. But the vaccine's effectiveness against the specific circulating strain varies wildly by season and by subtype. Over five seasons, effectiveness against H3N2 in people 65 and older was only 14%, with a confidence interval that crossed zero, meaning it might have done nothing at all [19]. Against H1N1 and B strains it was better, around 49-62% [19].
| Outcome | Unvaccinated | Vaccinated | What the evidence says |
|---|---|---|---|
| All-cause mortality (bias-adjusted) | baseline | ~36% lower | Observational, not RCT [5] |
| Hospitalization for pneumonia (bias-adjusted) | baseline | ~25% lower | Observational, not RCT [5] |
| VE against H3N2 in 65+ | baseline | 14% (CI crosses zero) | Pooled test-negative design [19] |
| VE against H1N1 in 65+ | baseline | 49% | Pooled test-negative design [19] |
| VE against B in 65+ | baseline | 62% | Pooled test-negative design [19] |
There is also a signal worth noting. One study found that current-season vaccination was associated with a tripling of the odds of death in older hospitalized patients, though the confidence interval was wide [17]. That could be a statistical fluke, or it could be a real effect from immune imprinting or from the vaccine blunting the wrong arm of the immune response. The fact that it appears at all, in a literature that mostly publishes positive results, means it deserves investigation, not dismissal.
My call: the flu shot probably reduces your risk of a bad outcome from influenza by a modest amount, but the evidence is observational, the benefit varies hugely by season and strain, and the long-term safety data is thin. Confidence: moderate for a small benefit in a typical season, low for any benefit in a mismatched season.
Sources examined 27
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Estimating mortality associated with seasonal influenza among adults aged 65 years and above in China from 2011 to 2016: A systematic review and model analysis
A systematic review and model-based analysis estimated seasonal influenza–associated mortality among Chinese adults aged 65+ from 2011–2016, revealing substantial excess mortality in respiratory, circulatory, and all-cause outcomes with large provincial variation and policy impl…
DOI: 10.1111/irv.13067 -
The Japanese Experience with Vaccinating Schoolchildren against Influenza
A long-term ecological time-series analysis comparing Japan and the United States shows that mass vaccination of Japanese schoolchildren against influenza markedly reduced winter excess mortality—particularly among the elderly—and that substantial deaths were averted in associat…
DOI: 10.1056/NEJM200103223441204 -
Influenza-associated disease burden in mainland China: a systematic review and meta-analysis
An evidence synthesis and meta-analysis estimating influenza-associated mortality, hospitalization, and outpatient burden in mainland China from 2005–2019, highlighting the highest burden among adults ≥65 and children <5 and assessing sources of heterogeneity to inform vaccinati…
DOI: 10.1038/s41598-021-82161-z -
Effectiveness of bivalent COVID-19 boosters against COVID-19 mortality in people aged 65 years and older, Australia, November 2022 to May 2023
In Australians aged 65+, recently administered bivalent boosters reduced COVID-19 mortality more than ancestral monovalent boosters during Nov 2022–May 2023, with strongest protection within 8–90 days and waning thereafter.
DOI: 10.2807/1560-7917.es.2023.28.47.2300603 -
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 -
LB20. Impact of School-Located Influenza Vaccination on Vaccination Coverage, School Absenteeism, and Influenza Hospitalization
Late-breaker abstracts show RSV F nanoparticle vaccine immunogenicity in pregnancy, school-located influenza vaccination benefits, and preemptive therapy reduces CMV disease after liver transplant.
DOI: 10.1093/ofid/ofy229.2194 -
Association between influenza vaccine effectiveness and chronic diseases among older adults with dementia
This study investigates the effectiveness of influenza vaccination in reducing hospitalization rates, pneumonia incidence, and antibiotic use among older adults aged 80 and above with dementia, revealing that unvaccinated individuals had the highest incidence of pneumonia, while…
DOI: 10.1038/s41598-025-10633-7 -
Interventions to prevent pneumonia in older adults
Interventions to prevent pneumonia in older adults—including capsaicin, amantadine, ACE inhibitors, cilostazol, folic acid, oral hygiene, and vaccines—are reported to reduce pneumonia incidence or hospitalization in older adults, particularly those with silent aspiration or immo…
DOI: 10.1111/j.1447-0594.2004.00162.x -
Impact of Vaccination on Hospitalized Adults With Influenza A, 2012–2013
A retrospective chart review at the University of Michigan Health System during the 2012-2013 influenza season evaluated whether prior influenza vaccination influences clinical outcomes among adults hospitalized with influenza A, finding vaccination was associated with lower lik…
DOI: 10.1097/ipc.0000000000000214 -
Effects of a Personalized Music Intervention Among Older Adults with Dementia
A compilation of abstracts from long-term/post-acute care research presenting findings on high-dose influenza vaccination in LTC residents, coma emergence therapy with neuro-stimulants, condition-specific SBAR to reduce transfers, personalized music interventions for dementia, f…
DOI: 10.1016/j.jamda.2015.12.079 -
Community-acquired pneumonia in Chile: the clinical relevance in the detection of viruses and atypical bacteria
A prospective, multi-diagnostic study of adults with community-acquired pneumonia in Santiago, Chile, applying conventional and molecular methods to identify viruses and atypical bacteria, finding that viral and atypical pathogens are detected as frequently as Streptococcus pneu…
DOI: 10.1136/thoraxjnl-2013-203551 -
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 -
Pneumococcal, Influenza, Hepatitis B, and Tetanus Vaccination Rate and Vaccine Awareness in Patients with Type 2 Diabetes
Vaccination uptake among Turkish adults with Type 2 diabetes is suboptimal, with only about half vaccinated and less than half aware of vaccination needs, across influenza, pneumococcal, hepatitis B, and tetanus vaccines, signaling a need for targeted awareness campaigns.
DOI: 10.25179/tjem.2020-75288 -
Changes in the incidence, viral coinfection pattern and outcomes of pneumococcal hospitalizations during and after the COVID-19 pandemic
Incidence of pneumococcal hospitalizations fell during the COVID-19 era and rebounded afterward, with influenza coinfection driving most monthly cases and COVID-19 coinfection rising post-pandemic, both coinfections linked to worse outcomes.
DOI: 10.1186/s41479-025-00164-0 -
The relative burden of community-acquired pneumonia hospitalizations in older adults: a retrospective observational study in the United States
This retrospective analysis of 1.95 million older adults in a large U.S. Medicare Advantage population compares the burden and costs of community-acquired pneumonia (CAP) hospitalizations to myocardial infarction (MI), stroke, and osteoporotic fractures (OF), finding CAP to have…
DOI: 10.1186/s12877-018-0787-2 -
Pneumococcal carriage and disease in adults hospitalised with community-acquired pneumonia in Mongolia: prospective pneumonia surveillance program (2019–2022)
A three-year, multicenter prospective study in four districts of Ulaanbaatar, Mongolia, characterizing pneumococcal carriage and pneumonia among adults hospitalized with clinical pneumonia, detailing serotype distribution (PCV13 vs non-PCV13), the impact of the COVID-19 pandemic…
DOI: 10.1186/s41479-025-00184-w -
Healthy-vaccinated effect
The study by Casado et al. demonstrates that repeated influenza vaccination significantly reduces the risk of severe influenza in older hospitalized patients, although it raises concerns about increased mortality in those vaccinated in the current season.
DOI: 10.1503/cmaj.69406 -
T Cell Transcriptional Signatures of Influenza A/H3N2 Antibody Response to High Dose Influenza and Adjuvanted Influenza Vaccine in Older Adults
This randomized trial in 234 older adults identified CAMK4, TMEM38B, and CREBBP as key CD4+ T cell transcriptional regulators differentially associated with influenza A/H3N2 HAI antibody responses to high-dose (Fluzone) vs. adjuvanted (Fluad) influenza vaccines, with 42 enriched…
DOI: 10.3390/v14122763 -
Influenza vaccine effectiveness in older adults compared with younger adults over five seasons
This study conducted a pooled analysis of influenza vaccine effectiveness over five seasons, comparing older adults (aged 65 years and above) with younger adults (aged 18-49 years), and found no significant differences in vaccine effectiveness between the two groups across vario…
DOI: 10.1016/j.vaccine.2018.01.045 -
Enhancing flu vaccine responses in older adults: preliminary insights from the ISOLDA study on immunosenescence and antioxidant and anti-inflammatory approaches
A pilot translational study in 52 adults (young vs older) examines how aging and influenza vaccination shape T cell immunophenotypes and humoral responses, and tests the anti-inflammatory/antioxidant effects of oleuropein alone or with the p38 MAPK inhibitor BIRB 796 on influenz…
DOI: 10.1186/s12979-025-00506-y -
DYNAMIC cohort study evaluating metabolic predictors of influenza vaccine immune response in older adults
A Singaporean prospective cohort of older adults examined how metabolic factors (diabetes, obesity, baseline vitamin D) and physical activity predict influenza vaccine–induced humoral immunity, finding that physical activity enhances HAI fold rise (especially for A/HK/H3N2) whil…
DOI: 10.1038/s41541-022-00548-z -
Relative Effectiveness of MF59 Adjuvanted Trivalent Influenza Vaccine vs Nonadjuvanted Vaccines During the 2019–2020 Influenza Season
In a large US retrospective cohort of adults aged 65 and older using linked electronic medical records and claims data, MF59-adjuvanted trivalent influenza vaccine (aIIV3) showed higher relative effectiveness against influenza-related medical encounters than egg-derived quadriva…
DOI: 10.1093/ofid/ofac167 -
Positive mood on the day of influenza vaccination predicts vaccine effectiveness: A prospective observational cohort study
This study investigates the impact of positive mood on the effectiveness of influenza vaccination in older adults, finding that a positive mood on the day of vaccination significantly predicts better immune responses.
DOI: 10.1016/j.bbi.2017.09.008 -
Chinese older people in Hong Kong: health beliefs about influenza vaccination
This study investigates the health beliefs regarding influenza vaccination among 70 unvaccinated Chinese older adults in Hong Kong, revealing that many perceive themselves as low-risk despite having chronic illnesses, and suggests that community nurses should work to modify thes…
DOI: 10.7748/nop2008.09.20.7.29.c6696 -
Impact of influenza vaccination on healthcare utilization – A systematic review
A systematic review evaluating the impact of seasonal influenza vaccination on healthcare utilization in older adults (65+), finding modest protection for outpatient visits but substantial heterogeneity and overall low-quality evidence that prevents a definitive conclusion about…
DOI: 10.1016/j.vaccine.2019.04.051 -
Effectiveness of Influenza Vaccine for Preventing Laboratory-Confirmed Influenza Hospitalizations in Adults, 2011–2012 Influenza Season
During the 2011-2012 influenza season, vaccination was 71.4% effective (95% CI, 17.1%-94.9%) in preventing laboratory-confirmed influenza-associated hospitalizations among adults with acute respiratory illness.
DOI: 10.1093/cid/cit124 -
Does Influenza Vaccination Modify Influenza Severity? Data on Older Adults Hospitalized With Influenza During the 2012−2013 Season in the United States
This study investigates the effect of influenza vaccination on disease severity in adults aged 50 years and older hospitalized with laboratory-confirmed influenza during the 2012-13 season, finding a modest effect on ICU length of stay for vaccinated individuals aged 50-64 years.
DOI: 10.1093/infdis/jiv200