Question explored with the scientific record
Do vaccines save lives?
The short version: the evidence shows vaccines reduce deaths from specific diseases in specific populations, but the effect varies enormously depending on the vaccine, the population, and the study design.
The strongest evidence comes from the HBV vaccination program, where multi-country data shows HBsAg carriage dropping from 11–19% before vaccination to 0–3% after [24]. That's a decline of roughly 85–95% in chronic infection, which is the main cause of liver cancer and cirrhosis deaths. The rotavirus vaccine cut US childhood hospitalizations by about 30,000 per year [1], and maternal influenza/pertussis vaccination was linked to a 34–42% lower infant mortality in an Australian cohort of 277,979 births [5]. The CAPiTA trial, the only randomized controlled trial here, found PCV13 cut vaccine-type pneumonia by 74% in adults 65+ [2].
But look at what is missing. The pneumococcal vaccine meta-analysis found 100% heterogeneity (I²=100) on most outcomes, meaning the studies disagree wildly [15]. Influenza vaccine effectiveness in the elderly drops to about 4.6% when bias adjustment is applied [12], not the 50% often claimed. The COVID-19 booster study found protection waned from 66% to 18% within six months [16]. And the Australian COVID-19 analysis reported that each million doses was associated with 400–700 excess deaths, with effect growing over successive waves [17]. That paper is ecological and has no control group—but it points to the kind of long-term signal the system rarely studies.
| Vaccine / Population | Outcome | Effect | Source |
|---|---|---|---|
| HBV, infants (multi-country) | Chronic carriage | 85–95% reduction | [24] |
| Rotavirus, US children | Hospitalizations | ~30,000 fewer/year | [1] |
| Maternal influenza/pertussis | Infant mortality (1yr) | 34–42% lower | [5] |
| PCV13, 65+ (CAPiTA) | Vaccine-type pneumonia | 74% reduction (RCT) | [2] |
| Influenza, elderly (bias-adjusted) | All-cause mortality | 4.6% reduction | [12] |
| COVID-19 bivalent, 65+ | COVID death (8–90 days) | 66% rVE, then wanes | [16] |
| COVID-19 injections (Australia) | Excess death per million doses | 400–700 deaths | [17] |
My call: vaccines save lives for diseases like hepatitis B and rotavirus where the evidence is consistent and the mechanism is clear. For influenza in the elderly and COVID-19 boosters, the benefit is smaller, is short-lived, and has poorly studied long-term harms. Confidence: high for HBV and rotavirus, moderate for maternal pertussis/influenza, low for influenza in the elderly, and not clear for repeated COVID-19 boosting given the emerging signal in the Australian ecological data.
Sources used 31
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All-Cause Gastroenteritis and Rotavirus-Coded Hospitalizations Among US Children, 2000–2009
This study evaluates the impact of the rotavirus vaccination program on gastroenteritis and rotavirus-coded hospitalizations among US children from 2000 to 2009, revealing significant reductions in hospitalization rates and associated costs post-vaccination.
DOI: 10.1093/cid/cis443 -
Pneumococcal Pneumonia and Invasive Pneumococcal Disease in Those 65 and Older: Rates of Detection, Risk Factors, Vaccine Effectiveness, Hospitalisation and Mortality
Pediatric PCV vaccination programs create herd protection that reduces pneumococcal disease in seniors, while PPV23 shows variable protection in older adults and overall vaccination uptake remains suboptimal, highlighting the need for targeted nursing-home strategies and surveil…
DOI: 10.3390/geriatrics6010013 -
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 -
Neonatal and infant mortality after maternal influenza and pertussis vaccination: Probabilistically linked cohort study
A large population-based cohort in three Australian jurisdictions linked maternal vaccination data with infant outcomes to evaluate whether in-pregnancy influenza and/or pertussis vaccination affects neonatal and infant mortality, finding reduced all-cause infant mortality with …
DOI: 10.1080/21645515.2025.2587307 -
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 -
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 -
O-050: Incidence of benzodiazepine and related drug use in persons with and without Alzheimer's disease: the MEDALZ study
This study systematically reviews the efficacy, safety, and tolerability of commonly prescribed urological drugs for treating lower urinary tract symptoms (LUTS) in elderly patients, finding significant associations between certain vaccinations and reduced all-cause mortality in…
DOI: 10.1016/s1878-7649(15)30063-2 -
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 Vaccination of Healthcare Workers Is an Important Approach for Reducing Transmission of Influenza from Staff to Vulnerable Patients
This study investigates the impact of promoting influenza vaccination among healthcare workers on reducing influenza-related morbidity and mortality in elderly residents of long-term care facilities, demonstrating significant benefits during periods of influenza circulation.
DOI: 10.1371/journal.pone.0169023 -
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 -
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 -
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 -
Impact of the 1918 Influenza Pandemic in Coastal Kenya
A historical epidemiology study using colonial-era archives to quantify the 1918 influenza pandemic’s mortality, morbidity, and social disruption in Coast Province, Kenya, and to compare it with global estimates.
DOI: 10.3390/tropicalmed4020091 -
Effectiveness of pneumococcal vaccination in reducing hospitalization and mortality among the elderly: A systematic review and meta-analysis
A systematic review and meta-analysis of 35 studies (1997–2024) evaluating pneumococcal vaccination in the elderly, finding reduced all-cause hospitalization with vaccines but mixed, highly heterogeneous effects on pneumonia-related hospitalization and mortality across subgroups…
DOI: 10.1080/21645515.2025.2561315 -
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 -
Early Indication of Long-Term Impact of COVID Injections
Analysis of Australian mortality data through June 2023 suggests COVID injections caused successive waves of excess deaths at a 21-week lag, with a fulfilled prediction and progressively larger dose-response, indicating possible long-term harm.
DOI: 10.33140/mcr.07.048 -
HIV/AIDS—Mexico City 2008
The paper discusses the advancements in HIV prevention and treatment strategies presented at the 17th International Conference on HIV/AIDS, highlighting the importance of antiretroviral therapy and new drug developments in reducing transmission rates.
DOI: 10.1080/13102818.2008.10817602 -
Multidrug-Resistant Tuberculosis. Recommendations for Reducing Risk during Travel for Healthcare and Humanitarian Work
A CDC/ATS Special Article outlining risk-reduction strategies to prevent multidrug-resistant and extensively drug-resistant TB transmission among healthcare and humanitarian workers traveling to high-burden regions, including pre-travel risk assessment and screening, vaccination…
DOI: 10.1513/AnnalsATS.201309-312PS -
Targeted human papillomavirus vaccination for young men who have sex with men in Australia yields significant population benefits and is cost-effective
This study evaluates the effectiveness and cost-effectiveness of targeted human papillomavirus (HPV) vaccination programs for young men who have sex with men (MSM) in Australia, demonstrating that a boys vaccination program significantly reduces HPV-related diseases compared to …
DOI: 10.1016/j.vaccine.2017.07.078 -
Transgenic human dipeptidyl peptidase-4 Syrian hamsters support MERS coronavirus infection and contact transmission
Transgenic Syrian hamsters expressing human DPP4 support robust MERS-CoV replication and direct-contact transmission, enabling evaluation of antivirals and vaccines in a small animal model.
DOI: 10.64898/2026.05.26.725122 -
An Extended SEIR Model with Vaccination for Forecasting the COVID-19 Pandemic in Saudi Arabia Using an Ensemble Kalman Filter
An extended seven-compartment SEIR model including vaccination is combined with a Joint-Ensemble Kalman Filter to forecast COVID-19 dynamics in Saudi Arabia and assess vaccination impact, achieving accurate short-term forecasts (about two weeks) and demonstrating vaccination-dri…
DOI: 10.3390/math9060636 -
Immunoprophylaxis of perinatal infection with hepatitis B virus on the national scale
This study evaluates the effectiveness of passive and active immunoprophylaxis in preventing perinatal hepatitis B virus (HBV) transmission in Japan, demonstrating a significant reduction in persistent infections among infants born to HBeAg-positive carrier mothers.
DOI: 10.1016/j.hepres.2006.10.001 -
Toward elimination and eradication of hepatitis B
A comprehensive review arguing that hepatitis B could be eliminated and eventually eradicated through a combination of interrupting transmission, expanding vaccination and immunoprophylaxis, and treating chronically infected individuals, with Taiwan’s mass vaccination program hi…
DOI: 10.1111/j.1440-1746.2009.06165.x -
Mathematical Modeling of Epidemic Spread Using Nonlinear Differential Equations: Application to the SIR Model and Its Variants
Nonlinear compartmental epidemic models (SIR, SEIR, SEIRD) calibrated to real outbreak data forecast a 13.2% peak infection and 89% cumulative infections by day 200 in the baseline scenario, while transmission-reduction and vaccination scenarios dramatically lower total infectio…
DOI: 10.32792/utj.v20i3.421 -
Efficacy of COVID-19 Vaccine
A comprehensive synthesis of published COVID-19 vaccine efficacy across multiple platforms and regimens shows strong protection overall but variability by vaccine type and dosing schedule.
DOI: 10.3329/jopsom.v40i2.61799 -
Epidemiology and prevention of animal bite and human rabies in a rural community-One health experiment
This study evaluates the incidence of animal bites and human rabies in a rural community in India, demonstrating a significant reduction in animal bite cases following a One Health intervention that included rabies awareness and vaccination programs.
DOI: 10.1016/s2222-1808(14)60495-3 -
Progress toward Interruption of Endemic Measles Transmission in Tunisia
This study documents Tunisia's measles elimination efforts (late 1990s–2002) through high vaccination coverage, targeted campaigns, and strengthened surveillance, showing interruption of indigenous transmission since 1999 with a 2002 outbreak due to importations and genotype B3 …
DOI: 10.1086/368050 -
Feline high pathogenicity avian influenza H5N1 infection: past and present
A 2025 literature review summarizing what is known about feline infections with high pathogenicity avian influenza A(H5N1) clade 2.3.4.4b, including epidemiology, clinical and pathological presentations, diagnostics, management, prevention, and the current assessment of cat-to-h…
DOI: 10.1177/1098612x251370695 -
The role of vaccines in combating antimicrobial resistance
The chapter/lecture argues that vaccination can reduce antimicrobial resistance by preventing infections, lowering resistant subtypes, and reducing bystander and hospital transmission, with evidence for certain vaccines and a call for expanded economic evaluations and a global g…
DOI: 10.1093/eurpub/ckaa165.1204 -
Dynamic models of pneumococcal carriage and the impact of the Heptavalent Pneumococcal Conjugate Vaccine on invasive pneumococcal disease
An age-structured dynamic transmission model parameterised with UK carriage/IPD data and US post-vaccination data predicts the impact of PCV7 on vaccine-type and non-vaccine-type pneumococcal carriage and invasive disease in England and Wales, showing serotype replacement can at…
DOI: 10.1186/1471-2334-10-90