COVID-19 vaccination: can smartwatches detect changes in cardiac response?

After the intense effort to massify vaccination against COVID-19 worldwide, it is time for booster doses and to analyze the substantial variability in the immune response of individuals to vaccines. There is currently no routinely available non-invasive method for objectively identifying a specific person's response to a vaccine beyond self-reported side effects.

The Centers for Disease Control and Prevention's (CDC) V-safe program found that most (69%) of the 1.9 million enrolled people reported some systemic side effects after the second dose of an mRNA vaccine. The ability to identify who is experiencing the expected immune response after vaccination could be of great value not only to manage the global trajectory of COVID-19, but also to help guide the development of new vaccines or to refine existing versions.

The reactogenicity of the vaccine can potentially lead to detectable physiological changes, so a group of specialists from the Scripps Research Translational Institute of La Jolla, California, in the USA. Department of Education, considered that they could detect an individual's initial physiological response to a vaccine by tracking changes using commonly used portable devices. The experts' research was published in NPJ Didital Magazine, a Nature medium.

During the pandemic, researchers from different disciplines addressed the ability of smartwatches to help detect COVID-19 or provide data on recovery. This latest study uses several measures of heart rate data to help track the progression of symptoms in someone who has coronavirus and to show how sick that person becomes while they are.

The paper analyzed sensor data on sleep, activity and heart rate of more than 5600 people. The findings showed that the latter index, on average, at rest increased significantly the day after vaccination, peaked two days later and returned to normal four days after the first dose and six days after the second dose. The effect appeared to be stronger after the second dose of the Moderna vaccine, compared to the Pfizer-BioNTech vaccine, and more pronounced in younger people.

The conclusions found suggest that previous COVID infection was linked to a significantly greater increase in resting heart rate after the first dose of the vaccine relative to those without previous infection. This detail is also “consistent with a greater immune response expected for these individuals,” the researchers stated in their paper.

“Investigating physiological signals in the period around vaccination can help us to better understand the variability of the response to the vaccine among people, as well as changes in an individual norm due to vaccination,” explained lead author Giorgio Quer, director of intelligence Artificial from Scripps. Because these individual changes are due to the initial immune response to the vaccine, they can potentially help guide future vaccine development to optimize their efficacy and safety, and enable more accurate individualized dose regimens.”

The team of researchers extracted their data from a major project, called Digital Engagement and Tracking for Early Control and Treatment (DETECT), a mobile application research platform that allows participants to share physiological and behavioral data collected through a physical activity or a smart watch, among those data are anything from manually entered symptoms, to test results or vaccination status.

Scientists analyzed the DETECT sensor data for two weeks before and after each vaccination dose. They compared the subsequent changes in resting heart rate, sleep, and activity levels of the participants with their baseline values. Their findings also showed that women experienced greater changes than men in resting heart rate in the five days after vaccination after the first dose, and that people under 40 had greater changes in resting heart rate, but only after the second dose. Activity and sleep patterns appeared to be minimally affected by the first dose, but immediately after the second dose there was a significant decrease in activity and an increase in sleep from baseline.

“While the link between physiological response and immune response still requires further research, digital monitoring could provide a novel way to identify people who may not be responding optimally to the vaccine,” concluded Steven Steinhubl, associate professor at Scripps and another of the authors of the document.

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