Physiological Response to COVID-19 Vaccine: Evidence for Sex Differences?

Background: Rapid development and implementation of vaccines constituted a crucial step in containing the COVID-19 pandemic. A comprehensive understanding of physiological responses to these vaccines is important to build trust in medicine.Methods: We investigated temporal dynamics before and after COVID-19 vaccination in four physiological parameters (breathing rate, wrist skin temperature, heart rate and heart rate variability) measured continuously by means of a wearable medical device for up to 9 months in a cohort of the general population in the Netherlands. Furthermore, we objectively assessed the duration of menstrual cycle phases before and after vaccination in menstruating participants.Findings: The recorded physiological signals demonstrated short-term increases in breathing rate and heart rate followed by a prompt rebound to baseline levels likely reflecting biological mechanisms accompanying the immune response to vaccination. No sex differences were evident in the measured physiological responses. In menstruating participants, we found a 0.8% decrease in the duration of the menstrual phase following vaccination.Interpretation: The observed short-term changes suggest that COVID-19 vaccines are not associated with long-term biophysical issues. Taken together, our work provides valuable insights into continuous fluctuations of physiological responses to vaccination and highlights the importance of digital solutions in health care.Funding: The COVID-RED project has received funding from the Innovative Medicines Initiative (https://www.imi.europa.eu) 2 Joint Undertaking under grant agreement No 101005177. This Joint Undertaking receives support from the European Union's Horizon 2020 (https://ec.europa.eu/programmes/horizon2020/) research and innovation programme and EFPIA (https://www.efpia.eu/).Declaration of Interest: AM, VK and BMG are past employees of Ava AG. TBB, DV, PK and BMG are current or past employees of Julius Clinical Research. MM is a current employee of P95 CVBA. The authors have no financial or personal conflicts of interest to declare.Ethical Approval: The study was approved by the responsible ethics committee (Medisch Ethische Toetsingscommissie [METC] Utrecht), and informed consent was provided by each participant.