Many are questioning whether they should receive the COVID-19 vaccination, especially since it is relatively new and mRNA vaccinations, while they have been in use, have not been widely used in the population.  Below is an attempt to provide a comparison, as much as possible, to assist in rational decision-making.  Medicine is very much an attempt at weighing the rewards with the risks to achieve the best possible outcome under the circumstances.  Most physicians recognize that this does not always yield the ideal result.

Despite what would appear to be inherent risks of COVID-19 vaccination, it should be appreciated that both Moderna and Pfizer attempted to include low-risk as well as high-risk patients in their vaccination studies.  In most cases, the adverse events did not appear to occur at a rate higher than that which occurs in the population at large.

Table I reviews the common adverse events with the vaccine compared with the same effect during natural COVID-19 infection.

Table II compares rates of more severe side effects of COVID-19 infection with  the same side effects of COVID-19 vaccination and the rate in the general population.

Table I:  Common adverse events of COVID-19 vaccination v. infection.

Statistic Without vaccination After COVID-19 Vaccination
Rate of contracting severe COVID-19 in Pfizer trial (7 d after 2nd dose)4 .08%





Rate of contracting severe COVID-19 (Moderna)3





Severity of infection with COVID-199 80% asymptomatic or mild

15% severe, requiring oxygen.

5% critical, requiring ventilation.


95% effective at preventing COVID-193,4

0% severe, requiring oxygen.

0% critical, requiring ventilation.

Number of patients with fever 80% of symptomatic COVID -19 patients10 14.8% of vaccinated patients (from vaccine, compared with 0.6% of placebo) in Moderna trial1; 14.2% in Pfizer trial4, 12
Number of patients with chills 63% of symptomatic COVID -19 patients10 43.4% of vaccinated patients (from vaccine, compared with 9.58 % of placebo) in Moderna trial1; 31.9% in Pfizer trial4, 12
Number of patients with fatigue 62% of symptomatic COVID -19 patients10 68.5 % of vaccinated patients (from vaccine, compared with 36.1 % of placebo) in Moderna trial1; 62.9% in Pfizer trial4, 12
Number of patients with headache 59% of symptomatic COVID -19 patients10 63 % of vaccinated patients (from vaccine, compared with 36.5 % of placebo) in Moderna trial1; 55.1% in Pfizer trial4, 12
Number of patients with shortness of breath 57% of symptomatic COVID-19 patients10 1 patient of vaccine group in Moderna trial (noted as resolving), otherwise noted in the placebo group3; shortness of breath was only noted in placebo group of Pfizer trial12


Table II:  Comparison of the more severe side effects of COVID-19 infection v. COVID-19 vaccination v. rate of occurrence in the general population.

Statistic During COVID-19 infection After COVID-19 Vaccination Rate in general population
Number of patients that develop blood clots5 31% of hospitalized COVID patients (81% of which are pulmonary emboli)5 Unknown but in none noted in trials3,4 1 in 1000/year in adults18
Number of patients with ischemic stroke6, 15 0.4-2.7 % of hospitalized COVID patient6, 15

As high as 6% in hospitalized COVID patients requiring intensive care16

Unknown. One patient hospitalized 32 days after 2nd vaccine of Moderna  trial but in 0 % in trials3, 4, 12; one patient with known pre-existing history of artherosclerosis died in Pfizer trial of arteriosclerosis 3 days after first vaccination  and rate of non-fatal stroke was .02%12 Prevalence is approximately 3% of adult population19
Number of patients with hemorrhagic stroke 0.2-0.9% of hospitalized COVID patients6, 15 Unknown but in 0 % in trial3, 4, 12 Prevalence is 13% of stroke20
Neurologic manifestations Covid‐19 onset in 419 of 509 patients hospitalized with covid (82.3%) at any time during disease2. Of these, rate of myalgias (44.8%), headaches (37.7%), encephalopathy (31.8%), dizziness (29.7%), dysgeusia (15.9%), and anosmia (11.4%)2 Headache occurred in 63% of vaccinated patients (from vaccine, compared with 36.5 % of placebo) in Moderna trial1 and 55.1% in Pfizer trial4, 12 but long-term unknown unknown long-term 1-year prevalence of headache is 46% and 64% lifetime prevalence32; Musculoskeletal pain prevalence in 13.5-47% of population with chronic widespread pain in 11.4-24%33; 12-month prevalence of dizziness in US is 14.8%34
Number of patients with Guillain-Barre Syndrome 2-4/816 patients hospitalized with COVID14 Unknown but not seen in trials3, 4, 12


1-2 people/100,00017
Number of patients with Bell’s palsy Case reports11 .0091-.009% in trials3, 4, 12 25-35/100,000/year13
Number of patients with cardiac issues In patients observed for a median time of 71 days: 78% demonstrate some cardiac involvement.

60% demonstrate ongoing myocardial inflammation.

7% fulminant myocarditis was likely cause of death7

In Pfizer trial 1 patient had cardiac arrest 62 days after 2nd vaccination and died 3 days later12; rate of nonfatal acute Myocardial infarction was .02%12 American adults diagnosed with heart disease is 12.1%35
Risk of ARDS from COVID-19 14.8% of patients hospitalized for COVID-19 (52.4% of which die from ARDS)8 0 % in vaccine groups of trials3, 4, 12 10-15% of hospitalized patients; 23% of mechanically ventilated patients26
Risk of Gastrointestinal disorders >50% (loss of appetite, nausea, vomiting, and diarrhea)10 Diarrhea or vomiting was noted in 3% vaccinated and 2% placebo patients in Pfizer trial 12; gastrointestinal disorder or diarrhea was noted in 2.8% and 1.2% of vaccinated patients (2.6% and 1.0% of placebo recipients), respectively in Moderna trial3 Incidence was 0.14 episodes per person-year in high income North America39
Acute respiratory distress syndrome 41.8% of 201 patients hospitalized with COVID, 52.4 % of whom died24 Unknown but 0 % in trials in vaccinated group3, 4, 12 10-15% of patients admitted to the intensive care unit40
Post-COVID pulmonary fibrosis 4% of patients with ARDS and a disease duration of less than 1 week, 24% of patients with a disease duration of between weeks 1 and 3, and 61% of patients with a disease duration of greater than 3 weeks, developed fibrosis23 Unknown; not noted in trials3, 4, 12 Incidence is 10.7 per 100,000/year for men and 7.4/100,000/year for women; prevalence is 20/100,000/ year for men and 13/ 100,000/ year for women27
Risk of Brain fog Of 120 patients hospitalized with COVID, 34% developed memory loss, 27% had concentration problems months later25 Unknown; not noted in trials3, 4, 12 25% of people over 75 years of age28
Lingering cough, shortness of breath, and chest pain Of 120 patients hospitalized with COVID-19, 17% had cough, 42% had shortness of breath, and 11% had chest pain months later7, 25 Unknown; not noted in trials3, 4, 12 Prevalence of shortness 27% globally29
Lingering fatigue Of 120 patients hospitalized with COVID, 55% developed lingering fatigue25 Unknown; not noted in trials3, 4, 12 71.34/100,000 persons30
Incidence of Multisystem Inflammatory Syndrome in Children 1659 cases from mid-May-October 1, 2020; 99% of which had COVID21 Unknown. Children were excluded from initial trial Kawasaki syndrome-associated hospitalization rate in 2006 was 28.0/100,000 in children < 5yo22
Cases of anaphylaxis N/A 21 cases out of 1,893,360 people who received the Pfizer vaccine26; in Pfizer trial 0.63% (vs. 0.51% in control group)12; no vaccine-associated anaphylaxis in Moderna trial3 Incidence 1.6-5.1 % and prevalence is 42/100,000-person-years31
Death Globally 2,115,125 deaths/ 98,529,820 cases (2.1%); U.S. 416,289 deaths/ 24,934,941 cases (1.7%)38 In Moderna trial, 6 deaths in vaccine group (7 in placebo group)3 In Pfizer trial, 2 deaths in vaccine group (4 in placebo group)12 867.8 deaths per 100,000 people in the U.S.37


In conclusion, the course of COVID-19 infection is complex and unpredictable.  Its interaction with the infected patient’s immune system is quite variable.  The infection itself can be challenging to overcome and many patients are laden with prolonged side effects.  In absence of previous history or likelihood of adverse reaction to the vaccine, while it may not be perfect and long-term side effects may come to light in the future, the risk versus reward ratio seems to be weighted in favor of vaccination.



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