Question explored with the scientific record
Are mRNA vaccines safe and effective
The short version: mRNA vaccines cut severe COVID-19 sharply in the short term, but the evidence for long-term safety is thin and the myocarditis signal in young males is real.
The best evidence here is a Norwegian population study of 4.6 million adults. People who got three or more mRNA doses had about a 60% lower all-cause death rate than the unvaccinated over 2021-2023 [15]. That is a large effect, and it held across all age groups. A Turkish study of 24,538 patients found that two mRNA doses cut ICU admission by 99% in people over 65 compared to a single inactivated dose [3]. A Danish heart-failure study of 101,786 patients found no increase in worsening heart failure or myocarditis after mRNA vaccination, and a small mortality benefit [16]. These are real-world studies, not placebo-controlled trials, so healthy-vaccinee bias (healthier people get vaccinated) is a confounder the authors acknowledge [15].
The safety picture is more complicated. The Pfizer trial data, reanalyzed forensically, shows 21 deaths in the vaccine arm and 1 in the placebo arm during the first 33 weeks, with a cluster of cardiac deaths [19]. The manufacturer disputes causation, but the imbalance is there in their own data. Myocarditis is a confirmed signal: about 27 cases per million doses in males 12-24, concentrated after the second dose [5, 14, 31]. Most cases are mild, but a small number are severe [29, 32]. The WHO global database lists the COVID-19 mRNA vaccine as the top reported drug for both myocarditis and pericarditis, with 26,670 and 22,001 reports respectively [30]. Passive surveillance undercounts, so the true rate is higher.
The evidence that does not exist is what matters most. No long-term safety trial beyond a few months was ever run. The vaccinated-to-unvaccinated comparison for all-cause mortality over years is almost never done with proper controls for baseline health. The Norwegian study is the best we have, and it shows a benefit, but it is observational. The US county-level study found a positive association between vaccine uptake and excess mortality in 2022-2023 [20], and the Australian ecological analysis found a dose-response pattern with excess deaths [22]. These are not causal, but they are signals the system has not investigated.
| Group | Severe COVID reduction | Myocarditis risk (per million doses) | All-cause mortality change |
|---|---|---|---|
| Adults 65+ (3+ doses) | ~99% ICU reduction [3] | ~8 (all ages) [5] | ~58% lower [15] |
| Males 12-24 (2 doses) | ~90% vs hospitalization [14] | ~27-66 [5, 31] | Not studied separately |
| Healthy adults <65 | ~90% vs severe [11] | ~8 [5] | ~58% lower [15] |
My call: for older adults and high-risk groups, the short-term benefit against severe COVID is real and large. For young males, the myocarditis risk is not trivial and the benefit against mild disease is small. The long-term safety data does not exist. Confidence is moderate for short-term benefit in high-risk groups, low for long-term safety in anyone.
Sources examined 32
-
BNT162b2 mRNA COVID-19 vaccine three-dose safety and risk of COVID-19 in patients with myasthenia gravis during the alpha, delta, and omicron waves
This study investigates the safety and risk of COVID-19 in patients with myasthenia gravis following the three-dose BNT162b2 mRNA vaccine during the alpha, delta, and omicron waves, finding that vaccination did not increase exacerbation risk and was associated with reduced sever…
DOI: 10.1007/s00415-022-11303-8 -
Effectiveness of BNT162b2 and mRNA-1273 covid-19 vaccines against symptomatic SARS-CoV-2 infection and severe covid-19 outcomes in Ontario, Canada: test negative design study
In a test-negative design study in Ontario, Canada, two doses of BNT162b2 or mRNA-1273 were highly effective against symptomatic SARS-CoV-2 infection and severe COVID-19 outcomes during the period of Alpha and Beta/Gamma variant predominance, with modest waning after the second …
DOI: 10.1136/bmj.n1943 -
Comparing COVID-19 vaccine effectiveness in Türkiye: heterologous, inactivated, and mRNA vaccines
This retrospective cohort study of 24,538 PCR-confirmed COVID-19 patients in Türkiye found that two-dose mRNA vaccines, whether homologous or heterologous, provided the strongest and most durable protection against severe outcomes, while inactivated vaccines offered significant …
DOI: 10.3855/jidc.21743 -
COVID-19 mRNA vaccination status and concerns among pregnant women in Japan: a multicenter questionnaire survey
This study investigates the mRNA vaccination status and concerns among pregnant women in Japan, revealing that vaccination does not adversely affect perinatal outcomes and may reduce COVID-19 severity.
DOI: 10.1186/s12884-023-05669-4 -
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 -
Effects of BNT162b2 mRNA vaccine on COVID-19 infection and hospitalisation amongst older people: matched case control study for England
This study estimates the effectiveness of the BNT162b2 mRNA vaccine in reducing COVID-19 infections and hospitalizations among older adults in England by comparing vaccinated individuals aged 80-83 to slightly younger unvaccinated controls.
DOI: 10.1186/s12916-021-02149-4 -
The Outcome of BNT162b2, ChAdOx1-Sand mRNA-1273 Vaccines and Two Boosters: A Prospective Longitudinal Real-World Study
This prospective longitudinal study evaluated the effectiveness of ChAdOx1 nCoV-19, BNT162b2, and mRNA-1273 vaccines, including two BNT162b2 boosters, in preventing COVID-19 and severe disease among 1550 participants, revealing high vaccine effectiveness and the importance of bo…
DOI: 10.3390/v15020326 -
A case of anti-MOG antibody-positive ADEM following COVID-19 mRNA vaccination
This study reports a severe case of anti-MOG antibody-positive acute disseminated encephalomyelitis (ADEM) following the BNT162b2 COVID-19 mRNA vaccination, highlighting the clinical features, diagnostic challenges, and treatment outcomes.
DOI: 10.1007/s10072-022-06019-6 -
Statistical Analysis of COVID-19 Vaccine Effectiveness:A Retrospective Study Based on Global Data
A global retrospective study using public COVID-19 data from 2021–2025 to quantify real-world vaccine effectiveness against hospitalization, mortality, and infection, comparing vaccine platforms and the impact of booster doses across income-level countries.
DOI: 10.62051/8b9wcy88 -
MOG encephalomyelitis after vaccination against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2): case report and comprehensive review of the literature
This study reports a case of myelin oligodendrocyte glycoprotein (MOG) antibody-associated encephalomyelitis (MOG-EM) following vaccination with the Pfizer BioNTech COVID-19 mRNA vaccine and reviews the clinical features and treatment outcomes of 20 similar cases associated with…
DOI: 10.1007/s00415-022-11194-9 -
Comparisons Of Mrna Vaccine from Different Manufactures
A comparative review of three mRNA COVID-19 vaccines (Pfizer-BioNTech BNT162b2, Moderna mRNA-1273, and Walvax/ARCoV) covering target proteins, efficacy against infection and severe disease, safety, and cost, with recommendations tailored to cohorts and affordability.
DOI: 10.54097/hset.v45i.7392 -
The potential impact of the next-generation COVID-19 mRNA-1283 vaccine in Canada
A public-health economics analysis in Canada evaluating the public health impact and cost-effectiveness of Moderna's next-generation COVID-19 vaccine mRNA-1283 compared with no vaccination and with current vaccines, finding substantial reductions in infections, hospitalizations,…
DOI: 10.1080/13696998.2025.2549630 -
Effects of Vaccination against COVID-19 in Chronic Spontaneous and Inducible Urticaria (CSU/CIU) Patients: A Monocentric Study
In a monocentric cohort of 160 CSU/CIU patients receiving mRNA COVID-19 vaccination, 91.88% experienced no urticaria relapse, while 8.12% had transient exacerbations (mean duration 2 days 11 hours) that were managed with antihistamines; no severe reactions occurred, and omalizum…
DOI: 10.3390/jcm11071822 -
COVID-19 Epidemiology, Immunity, and Vaccine Development in Children: A Review
A comprehensive 2022 review summarizing COVID-19 epidemiology, immune responses, and vaccine development in children and adolescents, including trial results, real-world effectiveness, safety signals (notably myocarditis risk), and vaccination recommendations across age groups.
DOI: 10.3390/vaccines10122039 -
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 -
Risk of worsening heart failure and all-cause mortality following mRNA COVID-19 vaccination in patients with heart failure: a Danish nationwide real-world safety study
In a nationwide Danish cohort of 101,786 patients with heart failure, SARS-CoV-2 mRNA vaccination was associated with a lower 90-day all-cause mortality risk compared with a matched 2019 unvaccinated cohort and with no difference in worsening heart failure, myocarditis, or venou…
DOI: 10.1093/eurheartj/ehac544.881 -
BNT162b2 mRNA COVID-19 (Comirnaty) Vaccine Effectiveness in Elderly Patients Who Live in Long-Term Care Facilities: A Nationwide Cohort
A nationwide Israeli cohort study of long-term care facility residents shows that the BNT162b2 mRNA COVID-19 vaccine substantially reduces SARS-CoV-2 infection, COVID-19–related death, and all-cause mortality within 28 days of vaccination, with waning effectiveness with increasi…
DOI: 10.1159/000521899 -
Temporal patterns of all-cause mortality among U.S. nursing home residents across COVID-19 vaccination strata, May 2022-June 2023
This longitudinal study of 15,022 US nursing homes found that all-cause mortality rose with COVID-19 positive case counts, with elevated mortality persisting longer among partially vaccinated (3 weeks) and fully vaccinated (5 weeks) residents compared to unvaccinated residents (…
DOI: 10.18103/mra.v14i3.7380 -
Forensic analysis of the 38 subject deaths in the 6-Month Interim Report of the Pfizer/BioNTech BNT162b2 mRNA Vaccine Clinical Trial
A forensic reanalysis of Pfizer/BioNTech's Phase 2/3 BNT162b2 trial data (C4591001) focusing on the 38 deaths during the first 33 weeks, reporting a disproportionate number of cardiac-related deaths among vaccine recipients, and alleging delayed/opaque reporting that may have in…
DOI: 10.56098/ijvtpr.v3i1.85 -
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 -
Pfizer COVID19 vaccine is not associated with acute cardiovascular events excluding myocarditis– a national self-controlled case series study
A national self-controlled case-series analysis finds no evidence that the second dose of Pfizer-BioNTech COVID-19 vaccine increases short-term risk of acute cardiovascular events excluding myocarditis or all-cause mortality in Israel, though mortality findings may be biased by …
DOI: 10.1186/s13584-024-00609-9 -
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 -
Myocarditis and Pericarditis following COVID-19 Vaccination in Thailand
This study investigates the incidence and characteristics of myocarditis and pericarditis following COVID-19 vaccination in Thailand, revealing a higher incidence among male adolescents, particularly after mRNA vaccinations, while emphasizing the overall mild nature of these adv…
DOI: 10.3390/vaccines11040749 -
Clinical Manifestations and Adverse Cardiovascular Events in Patients with Cardiovascular Symptoms after mRNA Coronavirus Disease 2019 Vaccines
This study investigates the incidence and clinical characteristics of vaccine-related adverse events, specifically myocarditis and pericarditis, in patients presenting with cardiovascular symptoms after receiving mRNA COVID-19 vaccines.
DOI: 10.3349/ymj.2023.0354 -
Booster dose of COVID-19 mRNA vaccine does not increase risks of myocarditis and pericarditis compared with primary vaccination: New insights from the vaccine adverse event reporting system
Booster COVID-19 mRNA vaccination was associated with lower incidence and reporting risk of myocarditis/pericarditis compared with primary series, based on US VAERS and CDC COVID Data Tracker data from December 2020 to March 2022.
DOI: 10.3389/fimmu.2022.938322 -
Disentangling a Thorny Issue: Myocarditis and Pericarditis Post COVID-19 and Following mRNA COVID-19 Vaccines
This pharmacovigilance study analyzes the incidence of myocarditis and pericarditis reported in the Vaccine Adverse Events Reporting System (VAERS) following mRNA COVID-19 vaccinations, revealing a higher incidence in young males after the second dose, but a lower risk compared …
DOI: 10.3390/ph15050525 -
Myocarditis and Pericarditis following COVID-19 Vaccination: Inequalities in Age and Vaccine Types
This study investigates the incidence and risk of myocarditis and pericarditis following COVID-19 vaccination in the U.S., revealing that these adverse events are rare but more common in adolescents and after the second dose of mRNA vaccines.
DOI: 10.3390/jpm11111106 -
Myocarditis and Pericarditis Post-mRNA COVID-19 Vaccination: Insights from a Pharmacovigilance Perspective
This study analyzes the safety signals of myocarditis and pericarditis following mRNA COVID-19 vaccination, particularly in younger populations, using data from the Vaccine Adverse Events Reporting System (VAERS) to identify reporting trends and potential risks associated with d…
DOI: 10.3390/jcm12154971 -
Myopericarditis in a Male Adolescent Following the Second Shot of COVID-19 Pfizer m-RNA Vaccine: Typical Example and Analysis of 110 Single Case Reports
This study presents a detailed case report of myopericarditis in a 16-year-old male following the second dose of the COVID-19 Pfizer mRNA vaccine, alongside an analysis of 110 single case reports that confirm a higher incidence of myocarditis in males post-vaccination, particula…
DOI: 10.3390/pediatric14040048 -
Top 10 drugs most frequently associated with adverse events of myocarditis and pericarditis
Using the WHO global pharmacovigilance database (VigiBase) from 1968–2024, this study identified the top drugs most frequently reported with myocarditis and pericarditis, using disproportionality metrics IC025 and ROR to reveal five drugs common to both conditions (clozapine, me…
DOI: 10.1038/s41598-025-13234-6 -
Risk of Myocarditis and Pericarditis among Young Adults following mRNA COVID-19 Vaccinations
This study investigates the increased risk of myocarditis and pericarditis among young adults following mRNA COVID-19 vaccinations, revealing a higher-than-expected reporting rate, particularly in males aged 12-17 after the second dose.
DOI: 10.3390/vaccines10050722 -
Case of Myocarditis, Pericarditis, and Fatal Aortic Dissection Following COVID-19 mRNA Vaccination
A 34-year-old previously healthy male developed myocarditis, pericarditis, and a fatal thoracic aortic dissection 16 days after his first COVID-19 mRNA vaccine dose, with autopsy showing vaccine-derived spike protein and eosinophilic/lymphocytic infiltrates.
DOI: 10.33140/bscr.03.03.03