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First major real-world analysis of side effects

Post-COVID vaccine, under 0.3% of Israelis reported side effects to doctor

‘People around the world should feel reassured,’ says public health expert; side effects similar to those seen after most other vaccines, Health Ministry reports

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

A Clalit Health Service-run vaccination center in Petah Tikva, January 27, 2021. (Miriam Alster/Flash90)
A Clalit Health Service-run vaccination center in Petah Tikva, January 27, 2021. (Miriam Alster/Flash90)

In the world’s most detailed data on how people feel after a Pfizer COVID vaccine, Israel has found that less than 0.3 percent had side effects they felt were significant enough to report to doctors.

The Health Ministry officials who released the research believe that it will provide peace of mind for many around the world who are eager to get a picture of the vaccine’s impact. They wrote that side effects are shown to be “similar in frequency and character to symptoms reported after other vaccines given to the population.”

They also stressed that side effects are normally “mild” and “soon pass.”

After the first shot, 6,575 of 2,768,200 Israelis sought medical assistance for side effects, which is 0.24%. The figure after the second shot was 0.26% — 3,592 of 1,377,827 recipients.

The latter figure indicates that while the second shot is known to leave some people feeling under the weather, this rarely escalates to formal medical complaints.

Israelis at a Clalit Health Service-run vaccination center in Petah Tikva, January 27, 2021. (Miriam Alster/Flash90)

Doctors responded enthusiastically to the data. “People around the world should feel reassured,” Yoav Yehezkeli, a physician and Tel Aviv University public health expert who was not involved in the study, told The Times of Israel.

Few complaints ended in hospitalization — an average of 17 patients per million after the first shot, and three patients per million after the second shot. Yehezkeli said doctors expected a few patients to have significant side effects, and he has personally treated a patient who had partial facial nerve paralysis after her second shot, but said the statistics show that incidence is low. His patient recovered.

It was the first major real-world analysis of side effects, involving many times the numbers involved in Pfizer’s clinical trials. Its findings, which are accurate to January 27, match the expectations held by health organizations around the globe on the basis of trial data.

America’s Centers for Disease Control and Prevention noted before the vaccine became available that it can cause side effects that are normally “mild to moderate,” while “a small number of people had severe side effects.”

The CDC expected the main side effects to be localized pain or broader symptoms like chills and headache, which “might feel like flu symptoms.” That was what the Israeli data found.

A medic in a protective suit and mask holds an injection syringe and vaccine. (oshcherban via iStock by Getty Images)

The vast majority of complaints were either localized pain in the arm, or people generally feeling unwell. Arm pain accounted for 50% of first shot complaints and 22% of second shot complaints. Some 41% of first shot complaints and 73% of second shot complainers reported feeling generally unwell.

There were also some more unusual side effects.

Neurological symptoms were reported by 287 first-dose vaccinees and 96 second-dose vaccinees. There were 165 reports of allergic reactions, including anaphylaxis, after the first shot and 47 after the second shot. Other unusual side effects were reported by 60 and 19 people after the first and second shots, respectively.

Israel’s statistics should be treated as reliable because the country’s health system involves “active surveillance” of side effects, said Yehezkeli. “They are important figures because many people in Israel have been vaccinated already and the healthcare system is very organized with methods of reporting side effects,” he commented.

“I’m a practicing physician and whenever I report a patient with, say, fever, who recently had a vaccination, the computer system generates an alert and asks me if I want to report it as a side effect. This is what I call active surveillance.”

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