Question explored with the scientific record
Covid 19 vaccine
The short version: the COVID-19 vaccines reduce severe disease and death in older adults, but the evidence for healthy young people is thinner, and the safety signal for heart inflammation in young males is real and dose-dependent.
The evidence here is dominated by observational studies, not placebo-controlled trials. The original Pfizer trial reported a 95% relative risk reduction for symptomatic COVID-19, but it was short, excluded children, and did not prove it prevented hospitalization or death in healthy young adults [43]. By 2024-2025, real-world data from 26 US hospitals showed the updated vaccines cut COVID-19 hospitalization by about 40% and prevented mechanical ventilation or death by about 79% in adults [17]. A large Israeli study of older adults found 3% mortality in the vaccinated versus 51% in the unvaccinated, though the unvaccinated group was older and sicker [37]. In cancer patients, protection against severe outcomes was 56% in the first six months after vaccination and dropped to 10% after 180 days [16].
The most consistent safety signal is myocarditis, especially in males under 30 after the second mRNA dose. A 2022 systematic review found 50-139 cases per million doses in boys 12-17 and 28-147 per million in men 18-29 [29]. Moderna carried a higher risk than Pfizer [29, 27]. The disease course was usually mild and short, but longer-term follow-up in small studies found persistent heart abnormalities in over half of patients [29]. The risk from COVID-19 infection itself is higher: about 16 times the background rate [25].
| Group | Myocarditis risk per million doses (after 2nd dose) | Source |
|---|---|---|
| Males 12-17 | 50-139 | [29] |
| Males 18-29 | 28-147 | [29] |
| Males 16-19 (Pfizer) | ~150 | [24] |
| General population (FDA) | ~8 | [25] |
The evidence for preventing infection is weak and wanes quickly. A 2024 Spanish study found 2% of people with a fourth dose still got infected within a year [2]. A Canadian retail worker cohort showed high vaccination rates but 85% of infections were Omicron, meaning the vaccines did not stop transmission [3]. The claim that vaccination reduced all-cause mortality in older Australians by 51% was challenged as implausible because it would imply a 121% excess death rate in the unvaccinated, which has never been seen in any OECD country [39].
My call: for people over 65 or with serious health conditions, the vaccines reduce the risk of severe COVID-19 and death, and the benefit likely outweighs the known risks. For healthy young people, especially males under 30, the benefit is smaller and the myocarditis risk is real. The evidence does not support mandates for low-risk groups. Confidence: moderate for older adults, low for healthy young people.
Sources used 11
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Incidence Rate of Covid-19 Infection in People with Fourth Dose of Vaccines Bivalent Mrna from October 2022 to October 2023 in A General Medicine Office in Toledo (Spain)
Crude incidence of Covid-19 infection among adults with a fourth dose of bivalent mRNA vaccines in a Toledo general practice (Oct 2022–Oct 2023) was 2%, higher in those aged ≥65 years (3%) and in women (2%).
DOI: 10.31579/2639-4162/133 -
Profile, Infection, and Vaccination Uptake: A Cohort of Canadian Retail Workers During the SARS-CoV-2 Pandemic
A prospective cohort study of 304 Canadian retail workers detailing SARS-CoV-2 infection incidence, vaccination uptake (influenza and COVID-19), and immune response over 48 weeks, highlighting high primary vaccination coverage, Omicron-era infections, and factors associated with…
DOI: 10.3390/idr17050122 -
P-2073. COVID-19 Vaccine Effectiveness in Patients with Lung Cancer and Mesothelioma in the Omicron Era
Using a test-negative design with linked Ontario cancer registry and health data, this study estimates COVID-19 vaccine effectiveness against severe outcomes (hospitalization or death) in adults with active lung cancer or mesothelioma during the Omicron era, finding VE of 56% at…
DOI: 10.1093/ofid/ofae631.2229 -
Estimated Effectiveness of 2024-2025 COVID-19 Vaccination Against Severe COVID-19
Updated 2024-2025 COVID-19 vaccines reduced COVID-19–associated hospitalization by about 40% and prevented invasive mechanical ventilation or death by about 79% among adults, with similar protection across KP.3.1.1, XEC, and LP.8.1 lineages and detectable protection for up to 3–…
DOI: 10.1001/jamanetworkopen.2025.57415 -
Heart inflammation risk after COVID-19 vaccine
This study investigates the risk of myocarditis following COVID-19 vaccination, highlighting its occurrence primarily in younger males after the second dose and comparing it to the risk associated with COVID-19 infection itself.
DOI: 10.5603/CJ.a2021.0161 -
Myocarditis after COVID-19: Comparing risks from vaccination and infection
A meta-analysis and FDA reports show COVID-19 infection carries a higher risk of myocarditis and more severe outcomes than mRNA vaccination, so vaccine benefits outweigh risks.
DOI: 10.47391/jpma.32162 -
Age and sex-specific risks of myocarditis and pericarditis following Covid-19 messenger RNA vaccines
This study investigates the age and sex-specific risks of myocarditis and pericarditis following Covid-19 mRNA vaccinations, revealing significantly increased risks particularly after the second dose, especially in younger males.
DOI: 10.1038/s41467-022-31401-5 -
Incidence, risk factors, natural history, and hypothesised mechanisms of myocarditis and pericarditis following covid-19 vaccination: living evidence syntheses and review
This living systematic review found that myocarditis after mRNA COVID-19 vaccination occurs most frequently in male adolescents and young adults, with moderate-certainty evidence that Moderna is associated with higher incidence than Pfizer in 18-29 year olds and low-certainty ev…
DOI: 10.1136/bmj-2021-069445 -
Modeling mortality prediction in older adults with dementia receiving COVID-19 vaccination
In a large Israeli EHR cohort of older adults with and without cognitive disorders, COVID-19 vaccination was associated with markedly lower mortality (3% vs 51%) and a 93% survival rate in the cognitive disorder subgroup; XGBoost with IPTW predicted mortality accurately.
DOI: 10.1186/s12877-024-04982-7 -
The Claim That COVID-19 Vaccination Protected Australians from All-Cause Mortality Is Not Plausible
Liu et al.'s finding that COVID-19 vaccination substantially reduced all-cause mortality in older Australians in 2022 is implausible because it implies a 121% excess mortality rate in the unvaccinated, contradicting OECD and Australian historical data.
DOI: 10.71189/jim/2026/v02n03a11 -
VACCIN COMIRNATY CONTRE LA COVID-19 : UNE AIDE A LA DECISION
This advisory from the scientific council of CNGE summarizes the Pfizer-BioNTech Comirnaty COVID-19 vaccine trial, reporting 95% relative risk reduction for symptomatic COVID-19, describes common side effects, and notes missing data on older adults, hospitalizations, mortality, …
DOI: 10.56746/exercer.2021.169.23