Assessment of multiple domains of pain following BNT162b2 mRNA COVID-19 vaccination.

Pain at the injection site is the most frequent reaction among COVID-19 vaccine recipients, but its characteristics were not fully described yet. The purpose of this study was to investigate multiple domains of pain following BNT162b2 mRNA vaccination. We included 107 subjects undergoing primary shot of the vaccination twice into deltoid muscle with a 3-week interval. They completed 6 sessions of pain assessments, one before the first and second dose (1-0, 2-0), and 1st/7th day after the first and second dose (1-1/1-7, 2-1/2-7). Pain visual analog scale (VAS), pain distribution, and pressure pain threshold (PPT) on deltoid muscle were evaluated in each session. The mean VAS (at rest/shoulder motion) was 6.0/27.6 mm at 1-1, and 12.8/34.0 mm at 2-1. Approximately, 90% of recipients showed localized pain within the upper arm. Percentage change of PPTs at 1-1 and 2-1 was bilaterally (ipsilateral/contralateral) decreased to 87.4/89.4% and 80.6/91.0%, which was recovered to the baseline level at 1-7 and 2-7. Temporary, mild-to-moderate intensity, localized distribution, concomitant with bilateral mechanical hyperalgesia on the deltoid muscle, were typical pain characteristics following this vaccination. These findings provide a rationale that will be informative for future recipients. J. Med. Invest. 70 : 355-360, August, 2023.