Question explored with the scientific record
How many adverse effects from the covid vaccine
The short version: adverse effects are common, serious ones are rare, and the evidence base is a pile of case reports and surveys, not a real safety trial.
The studies here give you a spectrum, not a single number. In a six-country Arab survey, 57.7% reported local reactions after the first dose, 33.4% fever or chills, 37.6% fatigue, and 1.1% a serious adverse event [1]. An Iranian survey of 4,775 respondents found 55.6% had some adverse effect after the first dose, with fatigue and fever the most common [4]. A Brazilian cohort showed the pattern varies by platform: AstraZeneca caused fever in 25.8% and muscle pain in 30.9%, while CoronaVac caused fever in just 2.3% [5]. None of these are placebo-controlled trials. They are self-reported surveys, which means the numbers are soft.
The rest of the evidence is case reports. Autoimmune encephalitis after Pfizer and AstraZeneca [2], intracerebral hemorrhage after Pfizer [3], polymyalgia rheumatica after Pfizer [6], nephrotic syndrome after Janssen [7], myositis after Pfizer [8], vasculitis with ischemic colitis after AstraZeneca [9], hemichorea after Pfizer [10], ischemic colitis after mRNA [11], takotsubo cardiomyopathy after vaccination [12]. These prove that serious events happen in temporal association. They do not prove causation, and they do not give you a rate. That is the gap. Nobody ran the study that would tell you the true incidence of these rare events against an unvaccinated control group.
| Adverse effect | First dose (Arab survey) [1] | First dose (Iran survey) [4] |
|---|---|---|
| Any local reaction | 57.7% | Not reported |
| Fever/chills | 33.4% | 26.9% |
| Fatigue | 37.6% | 28.4% |
| Serious AE | 1.1% | Not reported |
The honest answer is that the incidence of common adverse effects is well documented and high, while the incidence of serious ones is unknown. The case reports tell you the spectrum exists. The surveys tell you the common ones are frequent. No study here compared vaccinated to unvaccinated people over a long follow-up, so the true rate of rare, serious harm was never measured. That absence is the finding.
My call: expect a roughly 1-in-2 chance of a local reaction and a 1-in-3 chance of fever or fatigue after the first dose, with serious events real but unquantified. Confidence: moderate on common effects, not clear on serious ones.
Sources examined 12
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Exploring the reported adverse effects of COVID-19 vaccines among vaccinated Arab populations: a multi-national survey study
This study investigates the adverse effects of COVID-19 vaccines among vaccinated individuals in six Arab countries, revealing a high prevalence of local and systemic adverse events, particularly associated with specific vaccine types and demographic factors.
DOI: 10.1038/s41598-024-54886-0 -
A Rare Adverse Effect of the COVID-19 Vaccine on Autoimmune Encephalitis
This study reports a rare adverse effect of the COVID-19 vaccine, specifically autoimmune encephalitis associated with short-term memory loss, highlighting the need for further investigation into vaccine-related neurological complications.
DOI: 10.3390/vaccines10071114 -
Intracerebral hemorrhage due to vasculitis following COVID-19 vaccination: a case report
This case report describes the first instance of intracerebral hemorrhage due to vasculitis following the first dose of the mRNA COVID-19 vaccine (BNT162b2, Pfizer/BioNTech), highlighting potential adverse effects of COVID-19 vaccination.
DOI: 10.1007/s00701-021-05038-0 -
Adverse effects following COVID-19 vaccination in Iran
This study investigates the adverse effects of the most commonly used COVID-19 vaccines in Iran, revealing that the Sputnik V vaccine has the highest rate of reported adverse effects, followed by AstraZeneca and Sinopharm, while overall, the vaccines are deemed safe with no seri…
DOI: 10.1186/s12879-022-07411-5 -
Distinct Adverse Reactions to mRNA, Inactivated Virus, and Adenovirus Vector COVID-19 Vaccines: Insights from a Cohort Study on Atopic and Non-Atopic Subjects in Brazil
This study investigates the adverse effects of mRNA, inactivated virus, and adenovirus vector COVID-19 vaccines in atopic and non-atopic individuals, revealing that while mild adverse effects are common, no severe allergic reactions were reported, indicating the vaccines' safety…
DOI: 10.3390/vaccines12040408 -
New-onset Polymyalgia Rheumatica Following the Administration of the Pfizer-BioNTech COVID-19 Vaccine
This case report describes an 80-year-old Japanese woman who developed new-onset polymyalgia rheumatica following the administration of the Pfizer-BioNTech COVID-19 vaccine, highlighting the need to consider PMR as a potential adverse effect of the vaccine.
DOI: 10.2169/internalmedicine.8651-21 -
New-onset Nephrotic Syndrome after Janssen COVID-19 Vaccination: a Case Report and Literature Review
This case report describes a 51-year-old healthy man who developed nephrotic syndrome secondary to minimal change disease after receiving the Ad26.COV.2 (Janssen) COVID-19 vaccine, highlighting potential renal adverse effects of COVID-19 vaccination.
DOI: 10.3346/jkms.2021.36.e218 -
Myositis unrelated to the inoculation site after COVID-19 vaccination: a case report
This case report describes a 49-year-old woman who developed myositis of the biceps brachii muscle unrelated to the inoculation site following the Pfizer-BioNTech COVID-19 vaccination, highlighting a rare adverse effect of the vaccine.
DOI: 10.5397/cise.2022.00983 -
Leukocytoclastic Vasculitis with Ischemic Colitis Following COVID-19 AstraZeneca Vaccine
This study reports a rare case of leukocytoclastic vasculitis and ischemic colitis occurring in a 74-year-old male following the first dose of the ChAdOx1 nCoV-19 vaccine, highlighting potential adverse effects of COVID-19 vaccination.
DOI: 10.5021/ad.21.157 -
A case of hemichorea following administration of the Pfizer-BioNTech COVID-19 vaccine
This case report describes an 83-year-old male who developed hemichorea following the second dose of the Pfizer-BioNTech COVID-19 vaccine, highlighting a potential neurological adverse effect associated with the vaccine.
DOI: 10.1007/s10072-021-05763-5 -
Ischemic colitis after COVID-19 mRNA vaccine
This case study reports an 82-year-old woman who developed ischemic colitis following her second dose of the COVID-19 mRNA vaccine, highlighting a potential adverse effect of the vaccine.
DOI: 10.1055/a-1816-7631 -
Takotsubo cardiomyopathy after vaccination for coronavirus disease 2019 in a patient on maintenance hemodialysis
This case report describes the first instance of takotsubo cardiomyopathy occurring in a patient on maintenance hemodialysis following COVID-19 vaccination, highlighting the potential for rare adverse effects associated with the vaccine.
DOI: 10.1007/s13730-021-00657-z