Researchers at Tel Aviv University (TAU) equipped close to 5,000 Israelis with smartwatches and monitored their physiological parameters over two years. Of those monitored, 2,038 received the booster dose of the coronavirus vaccine, allowing the researchers to objectively compare measures before and after the participants took the vaccine and to confirm the safety of the vaccine. From the analysis of this large amount of data, the researchers were able to evaluate the safety of the vaccines subjectively (what the participant reports), objectively (what the watch detects), and clinically (what the doctor diagnoses).

The research was carried out by PhD student Matan Yechezkel under the supervision of Professor Dan Yamin, Head of the Laboratory for Epidemic Research, and led in collaboration with Professsor Erez Shmueli, Head of the Big Data Laboratory, all of TAU’s Fleischman Faculty of Engineering. Other collaborators were Dr. Tal Patalon and Dr. Sivan Gazit, Director and Deputy Director of the Kahn Sagol Maccabi Research & Innovation Center (the research and innovation institute of Maccabi Health Services), as well as Dr. Amichai Painsky and Merav Mofaz of TAU. The results of the research were published on November 18, 2022, in Lancet Respiratory Medicine.

The researchers examined the safety of the booster by analyzing the medical files of 250,000 anonymous members of Maccabi Health Services with the approval of the Helsinki Committee.

“We wanted to test the safety of booster vaccines against the coronavirus,” Professor Yamin explains. “We conducted a large-scale, two-year clinical study during which we equipped 4,698 Israelis with smartwatches. The smartwatches were used to monitor a number of parameters such as heart rate, variation in heart activity, quality of sleep, and number of daily steps taken. In addition, the participants were asked to fill out daily questionnaires about their health status in a customized application that we developed. Finally, we analyzed data on potential unusual events from the medical files of a quarter of a million randomly selected, anonymous, insured members of the Maccabi Health Services.”

Since the medical file contains the date the booster vaccine was administered, researchers were able to compare the condition of the vaccinated patient with his/her baseline condition from 42 days before receiving the vaccine to the condition of 42 days after receiving the vaccine.  The data was obtained from the questionnaires, smartwatches, and records of the Maccabi Health Fund.

“We saw clear and significant changes after administration of the vaccine, such as an increase in heart rate compared to the pulse rate measured before vaccination,” Professor Yamin says. “Then we saw a return to the participant’s baseline, i.e., the pulse levels after vaccination returned to their previous levels after six days. Hence, our study confirms the safety of the vaccine. The research also allowed us to compare subjective and objective indicators and medical diagnosis of the same participant who received the first booster and a few months later the second booster. We found no difference in the physiological response recorded by the smart watches or that reported by the participant in the app.”

In fact, the smartwatches were even more precise, the researchers say. “The most surprising finding was that the watches were more sensitive than the people they were monitoring. Many participants reported fatigue, headache, etc. after receiving the vaccine, and after two or three days reported that they felt normal and well. In contrast, from examining their watches, we saw distinct changes in heart rate that continued for several more days. There were also vaccinated participants who did not report any side effects at all and yet definitely experienced physiological changes, based on data from their smartwatches. In other words, we learned that the smartwatches were more sensitive to changes in general feeling than the participants themselves.”

In the medical literature, twenty-five unusual side effects attributed to the coronavirus vaccine were reported, and the researchers paid special attention to look for rare cases of inflammation of the heart muscle (myocarditis) and pericarditis. Professor Yamin and his colleagues checked the frequency of these unusual side effects among a quarter of a million Maccabi members and found no increase in serious incidents of any kind associated with vaccination.

“If the watch reports any minor changes in the muscles, and the participant reports only significant changes he feels, the medical file tells us about unusual events diagnosed by the doctors as well as hospitalizations that may be related to vaccinations, with an emphasis on cardiac events,” Professor Yamin concludes. “We did a comprehensive analysis of all those twenty-five unusual side effects, and we did not see an increase in their incidence among those receiving the booster. We found the vaccine to be safe to use. The smartwatch sensors ‘felt’ that the vaccine was safe, the vaccinee himself reported that the vaccine was safe, and finally, the doctors determined that the vaccine was safe. The results of the study have far-reaching implications regarding objective testing of vaccine safety in the future.”