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Many people don't trust even repeated assurances from official sources that mRNA vaccines like the Pfizer/BioNTech Covid shots are safe. In fact it's not unusual for opinion leaders opposed to these vaccines, and their followers, to warn that the Covid vaccines are extremely dangerous and have already caused high levels of serious illness and thousands of deaths. Millions of Americans appear to be far more afraid of the vaccines than of the Covid virus itself, and continue to refuse vaccination.
Credit: Fibonnaci Blue/Flickr
A new, peer-reviewed study appearing in the New England Journal of Medicine injects solid data into this fraught debate. The study provides an accounting and analysis of adverse events that occurred among more than 800,000 people within 42 days of receiving the Pfizer vaccine in Israel between December 20, 2020 and May 24, 2021, compared to an equal number of carefully matched peers who remained un-vaccinated, and to 173,000 peers who were diagnosed with Covid during the same time period. All the data came directly from anonymized medical records.
It's the largest controlled, peer-reviewed study of the side-effects of the Pfizer vaccine to date--nearly 40 times larger than Pfizer's phase III study--and provides the most accurate and detailed evidence to date of its risks when administered to large numbers of people on a national basis.
Anyone interested in reading the full research paper, carried out by researchers at the Clalit Institute in Israel and Harvard Medical School, can find it here.
The study evaluated 25 potentially serious adverse effects that earlier studies and clinical experience since the vaccines were released had identified as possibly linked to the Pfizer or other Covid vaccines, or to Covid itself. It did not look at mild, short-lived symptoms that typically accompany many vaccinations, such as fever, tiredness, or soreness near the injection site. It also did not attempt to evaluate any potential long-term effects.
Results:
Of the 25 adverse effects studied, 5 appeared more frequently following vaccination than they did in the same time period in the group of matched, but un-vaccinated peers:
Myocarditis--inflammation of the heart muscle--was 3.24 times more frequent in the vaccinated vs. un-vaccinated groups. However, since the incidence was low overall, that meant just 2.7 extra events per 100,000 people. In this study 91 percent of cases occurred in young men.
Lymphadenopathy--swollen lymph nodes--were 2.43 times more frequent among vaccinated compared to un-vaccinated people, appearing in 78.4 more cases than expected per 100,000. Swollen lymph nodes can be a sign of a serious condition such as cancer, but usually are simply an indication that the body is mounting an immune response.
Herpes zoster--shingles--was 1.43 times more frequent in the vaccinated group, and accounted for 15.8 additional cases per 100,000 vaccinated individuals.
Appendicitis occurred 1.4 times more often in vaccinated than unvaccinated individuals, adding 5 cases for every 100,000 people.
Bell's palsy--dysfunction of a facial nerve--occurred 1.3 times as often among the vaccinated group, but was also rare, accounting for 3.5 extra cases per 100,000 vaccinated individuals.
An unexpected finding was that vaccination lowered the risk of some of the adverse effects being studied, compared to the un-vaccinated group. Those included acute kidney injury, intracranial bleeding, anemia, and lymphopenia--low levels of white blood cells. The researchers suspect that those benefits appeared because of un-diagnosed Covid cases among the 800,000 un-vaccinated participants, which raised the incidence of those conditions--known complications of Covid-- in the un-vaccinated group.
As is true of almost any medical intervention, this study shows that the Pfizer/BioNTech mRNA vaccine is not risk-free. More importantly, the study gives us a clear measure of just what the vaccine's short- to medium-term risks are. Out of 25 potential side effects, 5 appeared at higher rates in the vaccinated vs. un-vaccinated groups. Of those, the most most serious was myocarditis, which added just 2.7 cases per 100,000, and the most frequent, which added 78 cases per 100,000, was not particularly serious--swollen lymph nodes.
In order to provide further context for those risks, the researchers looked at the same 25 potential adverse effects among 173,000 un-vaccinated study participants in the 42 days after they were diagnosed with Covid. The results reflect many of the all-too-well-known risks of Covid infection:
Cardiac arrythmia--3.8 times more frequent; 166 extra cases per 100,000
Acute kidney injury--14.8 times more frequent; 125.4 extra cases per 100,000
Pulmonary embolism--blood clot in the lungs--12.4 times more frequent; 61.7 extra cases per 100,000
Myocardial infarction--heart attack4.47 times more frequent; 25 extra cases per 100,000
Deep-vein thrombosis--3.78 times more frequent; 43 extra cases per 100,000
Myocarditis--18.3 times more frequent; 11 extra cases per 100,000
Pericarditis--5.39 times more frequent; 10.9 extra cases per 100,000
Intracranial bleeding--6.89 times more frequent; 7.6 extra cases per 100,000
Relative risks from Pfizer vaccination vs Covid infection
Credit: Noam Barda et al./NEJM
The vaccine is not risk free, but equally clearly, it does not cause anything like the degree or kinds of risk that anti-vaccination advocates and believers warn of. And the risks from the vaccine pale in comparison to the far higher risks from a Covid infection.
Here's what Dr. Ran Balicer, the study's lead author, concludes:
"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. These data should facilitate informed individual risk-benefit decision-making, and, in our view, make a strong argument in favor of opting-in to get vaccinated, especially in countries where the virus is currently widespread."
I'd add that the United States, which leads the world in Covid cases and deaths, qualifies as one of those countries.
If you want to compare your own risks from the vaccine with your risks from Covid, here's an approach:
If you're in the US and you're not vaccinated, as a rough approximation you have about a one percent chance--1000 out of 100,000 people--of getting Covid in any given six-week period.
If you're vaccinated, your odds are somewhere between 10 and 20 times better, depending on where and with whom you live, work and recreate.
Six weeks is the same length of time used in the above study, so you can get an idea of your chance of developing any or all of the Covid complications that the study quantified.
To those conditions you can add yet another risk. Over the course of the pandemic in the US, 1.6 percent--1600 out of every 100,000 people--who were diagnosed with Covid died from it.
So, as a first approximation, your chance of coming down with Covid during a given six-week period--and dying from it--is about the same as your chance of getting a case of shingles within six weeks of a Covid vaccination.
From what I hear, shingles isn't fun, but dying is worse.
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REA 9/8/21
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