Side effects feared from vaccine are more common in COVID cases — Israeli study

Research on 2 million Israelis fails to find high incidence of any serious side effect post-inoculation; coronavirus patient 4 times more likely to get myocarditis than vaccinee

Nathan Jeffay is The Times of Israel's health and science correspondent

A health worker prepares a Covid-19 vaccine in Jerusalem, on August 24, 2021. (Yonatan Sindel/Flash90)
A health worker prepares a Covid-19 vaccine in Jerusalem, on August 24, 2021. (Yonatan Sindel/Flash90)

COVID is far worse than vaccines in elevating risk of myocarditis and other conditions that have been feared as post-inoculation side effects, Israeli research shows.

The authors of the peer-reviewed side effects study, thought to be the largest of its kind to date, say it offers new reassurance on the safety of the Pfizer vaccine. They believe that it should prompt a serious rethink among people who shun the shots because of the rare side effects.

“Anyone who has been hesitant to get vaccinated so far due to concerns about rare side effects such as myocarditis, should be aware that the risk is higher among unvaccinated people infected with the coronavirus,” said Prof. Ran Balicer, head of research at the Clalit Health Services, which produced the study.

The study looked at almost two million medical records, and failed to identify high incidence of any serious side effect post-vaccination — while finding that several conditions are less common than normal among the newly inoculated.

According to Balicer, it provides clear figures that put the incidence of side effects, which loom large in the minds of many, into perspective.

Balicer, a senior adviser to the Israeli government on the coronavirus, said: “So far one of the main motives for hesitation to get vaccinated has been a lack of information about possible vaccine side effects. This in-depth study provides reliable information on the safety of the vaccines, and we hope it will help those who have not yet decided on the vaccine.”

One of the most discussed vaccine side effects, a heart condition called myocarditis, was found to be elevated among vaccinated people, with 2.7 more cases per 100,000 people than would normally occur (known as surplus cases). But among people who didn’t vaccinate and subsequently caught COVID-19 and recovered, surplus cases stood at 11 per 100,000.

Professor Ran Balicer, head of innovation at Clalit, Israel’s biggest health services provider, in Tel Aviv on June 10, 2020 (EMMANUEL DUNAND / AFP)

The study, just published in the New England Journal of Medicine, focused on people who received the Pfizer vaccine, and tracked patients’ health for six weeks. The study concluded that “the BNT162b2 vaccine was not associated with an elevated risk of most of the adverse events examined.”

The main exceptions were lymphadenopathy, which enlarges lymph nodes, and shingles. There were 78 surplus cases of lymphadenopathy per 100,000 vaccinated people but only 3 among the unvaccinated and infected.

There were nine fewer cases of shingles per 100,000 among the unvaccinated population than the norm, but 16 surplus cases among vaccinated patients.

Health Minister Nitzan Horowitz at a temporary set up vaccination center in the Arab Israeli town of Kfar Qassem. August 23, 2021. (Yossi Aloni/FLASH90)

The data indicates that the conditions feared as side effects were largely in the normal range — or even less common than normal — among vaccinated people, but elevated among those who caught COVID-19.

Acute kidney injury and arrhythmia turned out to be less common among the vaccinated than would be expected. Yet among the unvaccinated and infected patients, there were surplus cases — as many as 125 and 166 per 100,000 in the case of acute kidney injury and arrhythmia respectively.

There were other conditions that were more common among recovered patients, but in the broadly normal range among the vaccinated. These included pulmonary embolism (62 surplus events per 100,000 among the infected), deep vein thrombosis (43 events), myocardial infarction (25 events), pericarditis (11 events), and intracranial hemorrhage (7.6 events).

Appendicitis was found higher than the norm among both vaccinated people and the unvaccinated infected to a similar level — with five and four surplus cases per 100,000 people respectively.

The research was conducted in partnership with Harvard University, which chose to study Israeli data because it is comprehensive. Marc Lipsitch, director of Harvard’s Center for Communicable Disease Dynamics, a co-author of the study, said that a major challenge of vaccine safety research is comparing like-for-like patients.

“This is especially challenging when it comes to vaccines that are advancing so fast, but Clalit’s extraordinary database makes it possible to design research that addresses these challenges in a way that builds confidence in the reliability of the research’s conclusions.”

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