Ever wondered just how common vaccine side effects really are? This blog post dives deep into the data, from the nearly universal sore arm to the rare risks of myocarditis and GBS, separating widespread reactions from serious but uncommon events.
Key Takeaways
- In the Pfizer-BioNTech phase 3 trial, 83.0% of participants aged 16-55 years reported pain at the injection site after the first dose
- In the Moderna phase 3 trial, 92.0% of participants reported injection site pain after the first dose, with severity mostly mild to moderate
- Pfizer trial supplementary data showed 71.6% of participants had injection site pain after second dose
- Fatigue reported in 59.1% after Pfizer dose 1 in trial
- Headache in 51.8% after first dose Pfizer
- Moderna trial: Fatigue 59.6% dose 1
- Rate of myocarditis in males 12-29 years after mRNA vaccine: 40.6 cases per million second doses
- Males 16-17yo: 105.9 myocarditis/pericarditis per million Pfizer dose 2 (95% CI 91.7-122)
- CDC: 12.6 cases per million mRNA second doses males 12-39yo
- Guillain-Barré syndrome (GBS) after J&J: 15.5 excess cases per million doses
- AstraZeneca: Observed vs expected GBS 2.49 (95% CI 2.05-2.99)
- CDC: GBS rate 1.4 per million J&J doses
- Cerebral venous sinus thrombosis (CVST): 3.23 per million AstraZeneca
- Thrombosis with thrombocytopenia syndrome (TTS) J&J: 3.83 per million doses
- VITT AstraZeneca: 1 in 50,000-100,000 UK
Covid vaccines commonly cause mild, short-lived side effects like arm pain and fatigue.
Cardiovascular Side Effects
- Rate of myocarditis in males 12-29 years after mRNA vaccine: 40.6 cases per million second doses
- Males 16-17yo: 105.9 myocarditis/pericarditis per million Pfizer dose 2 (95% CI 91.7-122)
- CDC: 12.6 cases per million mRNA second doses males 12-39yo
- Israeli males <30: RR 3.48 for myocarditis after dose 2
- VAERS: 1,626 myocarditis reports by June 2021 mRNA
- UK Yellow Card: 1,645 cardiac disorders Pfizer by 2022
- EudraVigilance: 25,000+ cardiac reports mRNA by 2023
- Females 30-39: 4.2 per million mRNA dose 2
- Moderna vs Pfizer: Higher myocarditis Moderna males 18-24: 31 vs 15 per million
- Booster: 3 cases per million in young adults
- Nordic study: Incidence 1.71 per 100,000 after mRNA
- French: 4.6 per 100,000 12-49yo mRNA
- Pericarditis males 12-17: 62.8 per million Pfizer dose 2
- J&J: No increased myocarditis signal
- AstraZeneca: TTS not cardiac primary, but some MI reports
- VAERS confirmed myocarditis: 827 by Oct 2021
- Kids 5-11: 1.5 per million Pfizer
- Military: 0.89 per 100,000 AstraZeneca, low mRNA
- EMA: Myocarditis confirmed rare
- Thailand study: 1 case in 1 million kids Pfizer
Cardiovascular Side Effects Interpretation
These statistics confirm that while the vaccines carry a real, measurable cardiac risk for a tiny fraction of recipients—most notably young males after a second mRNA dose—the consistent, minuscule rates across multiple massive datasets starkly illustrate how the benefits still overwhelmingly crush the risks for the vast, vast majority of people.
Local and Mild Side Effects
- In the Pfizer-BioNTech phase 3 trial, 83.0% of participants aged 16-55 years reported pain at the injection site after the first dose
- In the Moderna phase 3 trial, 92.0% of participants reported injection site pain after the first dose, with severity mostly mild to moderate
- Pfizer trial supplementary data showed 71.6% of participants had injection site pain after second dose
- CDC reports that 77% of adolescents aged 12-15 years experienced pain at injection site after Pfizer vaccine dose 1
- In AstraZeneca trial, 62.5% reported injection site pain after first dose
- Pfizer trial: 2.8% had severe pain at injection site after dose 1
- Moderna trial: 10.5% had moderate injection site pain after dose 1
- J&J Janssen single-dose trial: 58.6% reported injection site pain
- UK Yellow Card: Over 100,000 reports of injection site reactions for Pfizer by mid-2021
- VAERS data: 25,072 reports of injection site pain for mRNA vaccines as of Dec 2021
- EudraVigilance: 45,000+ injection site reactions for Comirnaty by 2022
- Israeli study: 67% local pain after BNT162b2 dose 1 in healthcare workers
- Canadian surveillance: 75% pain in arm post-Pfizer
- Pfizer trial: Redness at site in 4.4% after dose 1
- Moderna: Swelling in 14.7% after dose 1
- AstraZeneca: Local tenderness 59.7%
- Novavax trial: 81% pain after dose 1
- Sputnik V trial: 65.8% local reactions
- Sinovac trial: 25.3% local pain
- Bharat Biotech Covaxin: 13% local pain
- CDC V-safe: 54.2% pain after dose 1 Pfizer
- French ANSM: 80% local reactions Pfizer
- Australian TGA: 70% soreness post-vax
- Pfizer trial kids 5-11: 84.9% pain dose 1
- Moderna kids: 93.4% pain
- Booster Pfizer: 77.7% pain
- J&J booster: 65% pain
- VAERS: 5% with severe local reactions mRNA
- EMA: 1 in 10 injection site pain Comirnaty
Local and Mild Side Effects Interpretation
While the overwhelming consensus across global data shows that a sore arm is a remarkably common, if not almost expected, post-vaccine souvenir, the severity is reassuringly mild for the vast majority, meaning your bicep might complain for a day, but your immune system is throwing a far more effective victory party.
Neurological Side Effects
- Guillain-Barré syndrome (GBS) after J&J: 15.5 excess cases per million doses
- AstraZeneca: Observed vs expected GBS 2.49 (95% CI 2.05-2.99)
- CDC: GBS rate 1.4 per million J&J doses
- UK: 227 GBS cases AstraZeneca early 2021
- VAERS: 200+ GBS reports J&J by 2021
- French: GBS 100 cases per 1M AstraZeneca
- mRNA vaccines: No increased GBS signal
- Bell's palsy: Pfizer trial 4 cases vs 0 placebo, not significant
- Moderna: Bell's palsy similar placebo
- VAERS: 1,000+ Bell's palsy mRNA
- Transverse myelitis rare reports
- Seizures: 0.02% in trials
- Encephalitis: Few cases VAERS
- UK: 400 neurological Pfizer
- Headache severe: 1.6% Pfizer dose 2
- Parasthesia: Reported in 0.5%
- Memory loss anecdotal, but 500+ reports VAERS
- Tremor: Rare, EMA lists
- Dementia reports increase post-vax claims, but unverified
- Optic neuritis: 50 cases UK
- Taste/smell alteration: 0.3%
Neurological Side Effects Interpretation
While Guillain-Barré syndrome presents a clear, though small, increased risk with adenovirus-based vaccines (J&J and AstraZeneca), the data for mRNA vaccines largely refutes widespread severe neurological side effects, instead painting a picture where common issues like headache are relatively frequent, very rare serious events are meticulously tracked, and a noisy background of anecdotal claims far outruns the established evidence.
Systemic Mild Side Effects
- Fatigue reported in 59.1% after Pfizer dose 1 in trial
- Headache in 51.8% after first dose Pfizer
- Moderna trial: Fatigue 59.6% dose 1
- AstraZeneca: Headache 53.1% dose 1
- J&J: Fatigue 37.1%
- Pfizer dose 2: Fatigue 62.9%
- Myalgia 38.0% Pfizer dose 1
- Chills 11.2% Pfizer dose 1
- Fever 16.0% Moderna dose 2
- V-safe: 46.4% fatigue after Moderna dose 1
- UK Yellow Card: Fatigue most common symptom, 250,000+ reports Pfizer
- CDC: 73.6% systemic reactions in 12-15yo Pfizer
- Israeli HCW: Fatigue 41% dose 1 BNT
- Novavax: Fatigue 64% dose 1
- Sputnik V: Fever 15.6%
- Covaxin: Headache 5.5%
- Booster Moderna: Fatigue 61.8%
- J&J: Headache 38.3%
- French: Fatigue 40-50% post-vax
- Australian: Headache 30%
- Pfizer kids: Fatigue 39.8%
- V-safe booster: 48% fatigue
- EMA: Very common fatigue (1/10)
- VAERS: 150,000+ fatigue reports mRNA early 2022
Systemic Mild Side Effects Interpretation
Despite the diverse symptoms and statistics, the data collectively suggests that feeling temporarily drained is the body’s most common, and often most vocal, receipt for the immune-building work it’s doing.
Thrombotic and Other Serious Side Effects
- Cerebral venous sinus thrombosis (CVST): 3.23 per million AstraZeneca
- Thrombosis with thrombocytopenia syndrome (TTS) J&J: 3.83 per million doses
- VITT AstraZeneca: 1 in 50,000-100,000 UK
- EMA: 8 cases TTS per million AstraZeneca <60yo
- CDC TTS J&J women 30-49: 9.0-16.1 per million
- Anaphylaxis: 4.7 cases per million Pfizer doses
- Moderna anaphylaxis 2.5 per million
- VAERS anaphylaxis: 4,100 reports mRNA 2021
- MIS post-vax rare, unlike infection
- Capillary leak syndrome AstraZeneca rare
- Death reports: VAERS 10,000+ unverified by 2022
- UK: 1,645 fatal reports all vaccines 2022
- EudraVigilance: 45,000 deaths reported EU by 2023, unconfirmed
- Pulmonary embolism: Increased signal AstraZeneca early
- Stroke ischemic: No clear signal mRNA
- Menstrual disorders: 30,000 reports UK
- Tinnitus: 10,000+ VAERS
- Chronic fatigue: Post-vax syndrome claims
Thrombotic and Other Serious Side Effects Interpretation
These statistics reveal that while severe vaccine side effects exist, they are extraordinarily rare events—akin to being struck by specific kinds of lightning—and their risk must be soberly weighed against the far greater, more common dangers of the virus they protect against.
Sources & References
- Reference 1NEJMnejm.orgVisit source
- Reference 2CDCcdc.govVisit source
- Reference 3GOVgov.ukVisit source
- Reference 4VAERSvaers.hhs.govVisit source
- Reference 5ADRREPORTSadrreports.euVisit source
- Reference 6MEDRXIVmedrxiv.orgVisit source
- Reference 7HEALTH-INFOBASEhealth-infobase.canada.caVisit source
- Reference 8THELANCETthelancet.comVisit source
- Reference 9ANSMansm.sante.frVisit source
- Reference 10TGAtga.gov.auVisit source
- Reference 11EMAema.europa.euVisit source
- Reference 12JAMANETWORKjamanetwork.comVisit source
- Reference 13BMJbmj.comVisit source
- Reference 14ACADEMICacademic.oup.comVisit source
- Reference 15FDAfda.govVisit source
- Reference 16OPENVAERSopenvaers.comVisit source