Question explored with the scientific record
Is the Covid 19 vaccine safe
The COVID-19 vaccines have a real, well-documented safety signal for myocarditis in younger males, while the evidence on all-cause mortality is contradictory and heavily shaped by who funded the study and how the comparison groups were chosen.
The most consistent serious harm is myocarditis, especially in males aged 12-39 after the second mRNA dose. A 2022 systematic review found incidence of 50-139 cases per million in male adolescents and 28-147 per million in young men [5]. The Moderna vaccine carries a higher risk than Pfizer in this age group [5]. A 2022 self-controlled case series in England reported a relative incidence of 56.48 for myocarditis after a second Moderna dose in 16-39 year olds [6]. While most cases resolve quickly, longer-term follow-up (3 months) in small case series found persistent abnormalities in over half of patients [5].
The evidence on all-cause mortality is a mess of conflicting studies, many funded or conducted by the same institutions that promoted the vaccines. A 2026 Norwegian study of 4.6 million adults found a lower mortality rate in the vaccinated, but the authors acknowledge this may reflect "healthy vaccinee bias" – healthier people were more likely to get vaccinated [3]. A 2025 UK analysis of ONS data found that all-cause mortality in vaccinated individuals increased over time relative to the unvaccinated, with predicted crossing points where the vaccinated group's risk exceeded the unvaccinated's [2]. A 2026 US county-level study of over 3,000 counties found a positive association between higher vaccine uptake and higher excess mortality in 2022 and 2023 [1]. A 2026 Japanese study found lower mortality in highly vaccinated elderly but higher mortality in younger adults (20-49) who received 5 or more doses [4].
My call: The vaccines clearly reduce the risk of severe COVID-19, but they carry a real, non-trivial risk of heart inflammation in young males, and the long-term net effect on all-cause mortality is not settled by the available evidence. Confidence: low that the full safety picture is known, given the conflicting mortality data and the absence of long-term, independently funded trials comparing vaccinated to unvaccinated populations.
Sources used 6
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Why COVID-19 vaccination cannot be ruled out as an explanation for all-cause excess mortality in the pandemic’s aftermath: A population-level study of over 3,000 US counties with over 320 million people
A US county-level study found positive associations between per-capita COVID-19 vaccine uptake and all-cause excess mortality in 2022 and 2023, even when adjusting for lagged mortality, but the design cannot establish causation.
DOI: 10.12688/f1000research.177279.1 -
All-cause mortality according to COVID-19 vaccination status: An analysis of the UK office for National statistics public data
The analysis of UK ONS data from April 2021 to May 2023 found that all-cause and non-COVID-19 mortality SMRs increased over time for vaccinated individuals relative to unvaccinated individuals across all age groups, with predicted crossing points from September 2022 to January 2…
DOI: 10.12688/f1000research.154058.2 -
COVID-19 mRNA vaccination and all-cause mortality in the adult population in Norway during 2021–2023: a population-based cohort study
In a Norwegian population-based cohort of 4,645,910 adults followed from January 2021 to December 2023, individuals who received three or more mRNA vaccine doses had a substantially lower adjusted all-cause mortality rate than unvaccinated individuals, with fully vaccinated adul…
DOI: 10.1136/bmjph-2024-001859 -
Age-specific patterns of all-cause mortality across COVID-19 booster dose groups in two Japanese municipalities: an exploratory analysis
Exploratory analysis of Japanese municipal registry data found lower all-cause mortality among highly vaccinated adults aged 65-89 years but higher all-cause mortality among adults aged 20-49 years with ≥5 doses and those aged 50-64 with six doses, with causality unestablished.
DOI: 10.3389/fpubh.2026.1795437 -
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 -
Risk of myocarditis and pericarditis after a COVID-19 mRNA vaccine booster and after COVID-19 in those with and without prior SARS-CoV-2 infection: A self-controlled case series analysis in England
In England, mRNA COVID-19 vaccine doses, especially second doses in males aged 16-39, elevated short-term risk of myocarditis admission; booster risks were lower and prior infection did not increase vaccine risk, but SARS-CoV-2 infection itself carried elevated myocarditis risk.
DOI: 10.1371/journal.pmed.1004245