(249) Real-Time Survey of Vaccine Safety of the mRNA-1273 SARS-CoV-2 Vaccine in Workplace Vaccination at Keio University

Publication Number: 923

Background: The mRNA-1273 Moderna COVID-19 vaccine, a new modality of mRNA-based vaccine, was first introduced to combat the COVID-19 global pandemic in 2020. Although the safety of the vaccine has been investigated worldwide, real-world safety data after the start of mass vaccination with COVID-19 vaccines at the workplace in Japan is lacking.

Objectives: This real-time survey was aimed to assess adverse events following immunization (AEFI) with mRNA-1273 COVID-19 vaccine in a real-world, workplace vaccination setting including three doses.

Methods: The workplace vaccination at Keio University took place using the mRNA-1273 COVID-19 vaccine between June 26 and September 3, 2021, for the first two doses and between March 22 and May 28, 2022, for the additional third dose. The target of workplace vaccination included students, faculty members, and administrative staff of Keio University in Tokyo, totaling approximately 25,000 people. An online survey of suspected AEFI was conducted in the samples of students, faculty members, and administrative staff of Keio University Faculty of Pharmacy. Participants were requested to take four surveys during the seven-day follow-up period after each dose.

Results: The maximum number of responses to the survey (301 participants) was obtained on Day 0 for the first dose. The majority of respondents reported local and systemic AEFIs, including injection-site pain, malaise, fever, and headache for first dose. A much larger number of respondents reported these systemic AEFIs for second dose, with a peak on Day 1. No noticeable difference in local reactions was seen between the first and second dose. While females reported more AEFIs after the first dose, the rate became closer as the number of male reports increased at the second dose. After stratification into young group aged 10-29 years and a middle-age group aged ≥30 years, reporting rate for the young group was higher than that for the middle age group after the first dose, but the difference decreased after the second dose. Most AEFIs were partially or completely resolved at Day 7 for both doses, except for known localized cutaneous hypersensitivity reaction for the first dose. More respondents used antipyretic analgesics for the second dose. The responses for the third dose are collecting at the time of abstract submission.

Conclusions: This real-time survey among a Japanese workplace vaccination population confirmed that the safety profile of mRNA-1273 COVID-19 vaccine in a real-world setting was similar to that derived from the premarketing randomized clinical trials. A high rate of AEFIs, including local and systemic reactions, were reported for both doses, especially for the second dose, albeit that these were not severe and probably resulted from the induced immune response.