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Largest Real-World COVID-19 Vaccine Study Confirms Overwhelming Safety


Stephen Luntz

Stephen has a science degree with a major in physics, an arts degree with majors in English Literature and History and Philosophy of Science and a Graduate Diploma in Science Communication.

Freelance Writer

israel vaccination center

Israel's early roll-out of the Pfizer/BioNTech COVID-19 vaccine was made possible by the promise of unique assessment capacity of its effects. An immense study has utilized this capacity to show side-effects are rare and mostly mild, while previously unnoticed consequences of infection are much more common and deadly. Image Credit: Igal Vaisman/

A comparison of the medical histories of vaccinated and unvaccinated Israelis shows side effects from the Pfizer/BioNTech vaccine are rare and predominantly mild. Among 25 possible side effects explored in the study only four were more common among those that had been vaccinated than those that were not, and all remained uncommon. Meanwhile, infection raised the risk of far more serious conditions to a much greater extent.

Myocarditis, inflammation of the heart muscle that can cause shortness of breath and irregular heartbeat, has been among the highest profile side effects of COVID-19 vaccination.


According to a study in the New England Journal of Medicine of a substantial proportion of the Israeli population, it does occur at a higher rate among the vaccinated, but not by much. An extra 2.7 individuals in 100,000 were diagnosed with myocarditis compared to the unvaccinated population who hadn’t caught the disease. Most excess cases were among men aged 20 - 34. However, even if myocarditis was your only fear, it would still be advisable to get the vaccine anywhere COVID-19 is common. Among unvaccinated people who caught the disease the excess rate was 11 per 100,000 – four times as high.

The study found that easily the most common adverse event triggered by Pfizer vaccination is swelling of the lymph glands, which happens at an extra rate of 78 cases per 100,000. However, as a normal response to illness and something we will overcome many time in our lives, it's best not to risk death by virus in order to avoid. Likewise, the 16 additional cases per 100,000 of shingles (reactivation of past chickenpox virus infections) are unpleasant, but hardly life-threatening. The final and more serious side effect, appendicitis, occurs at just 5 excess cases per 100,000.

Meanwhile, a variety of other effects examined in the study were no more common among the vaccinated, but increased dramatically among unvaccinated people who caught COVID-19. These included kidney damage, pulmonary embolism, deep vein thrombosis and stroke with 125, 62, 43 and 14 excess cases per 100,000 respectively, along with several others.

"These results show convincingly that this mRNA vaccine is very safe and that the alternative of 'natural' morbidity caused by the coronavirus puts a person at significant, higher and much more common risk of serious adverse events,” Professor Ran Balicer of the Clalit Research Institute said in a statement.


"To date, one of the main drivers of vaccine hesitancy has been a lack of information regarding potential side effects of the vaccine. This careful epidemiological study provides reliable information on vaccine safety, which we hope will be helpful to those who have not yet decided about vaccination,” added Harvard’s Dr Ben Reis.

Israel was able to secure access to some of Pfizer’s first vaccines in part because of its exceptional system of medical record keeping, which offered an opportunity to track the consequences of vaccination better than almost anywhere else in the world.

The paper’s authors made use of this to record the side effects experienced by 884,828 vaccinated individuals and compare these with the same number who did not get the vaccine, matched by age, sex, religion and known risk factors.

Where other investigations of vaccine effects rely on self-reporting, or doctors reporting effects to the VAERS database, this one includes every medical record for the individuals involved between December 20, 2020 and May 24. Consequently, events neither doctor nor patient may have thought connected to the vaccine have been included for testing, squashing vaccine-opponents’ claims that effects are being overlooked or even hushed up. Further detail was provided by comparing medical events among 173,106 unvaccinated individuals who caught COVID-19, and a demographically matched equal number who never tested positive.


Compared to clinical trials, studies like this involve much larger sample sizes, revealing differences in even very rare effects. They can also capture a longer time period, and a more diverse population in terms of age and previous health.



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