Reactogenicity following two doses of the BNT162b2 mRNA COVID-19 vaccine: Real-world evidence from healthcare workers in Japan

Abstract

As the first authorized COVID-19 vaccine in Japan, the BNT162b2 mRNA COVID-19 vaccine is utilized for mass vaccination. Although efficacy has been proved, real-world evidence on reactogenicity in Japanese personnel is needed to prepare the public. Healthcare workers in a large academic hospital in Japan received two doses of the Pfizer-BioNTech vaccine from March 17 to May 19, 2021. Online questionnaires were distributed to registered recipients following each dose, from day 0 through day 8. Primary outcomes are the frequency of reactogenicity including local and systemic reactions. Length of absence from work was also analyzed. Most recipients self-reported reactogenicity after the first dose (97.3%; n=3,254; mean age [36.4]) and after the second dose (97.2%; n=3,165; mean age [36.5]). Systemic reactions following the second dose were substantially higher than the first dose, especially for fever (OR, 27.38; 95% CI, [22.00-34.06]; p<0.001), chills (OR, 16.49; 95% CI, [13.53-20.11]; p<0.001), joint pain (OR, 8.49; 95% CI, [7.21-9.99]; p<0.001), fatigue (OR, 7.18; 95% CI, [6.43-8.02]; p<0.001) and headache (OR, 5.43; 95% CI, [4.80-6.14]; p<0.001). Reactogenicity was more commonly seen in young, female groups. 19.3% of participants took days off from work after the second dose (2.2% after the first dose), with 4.7% absent for more than two days. Although most participants reported reactogenicity, severe cases were limited. This study provides real-world evidence for the general population and organizations to prepare for BNT162b2 mRNA COVID-19 vaccination in Japan and other countries in the region.

Adverse reactions to the BNT162b2 and mRNA-1273 mRNA COVID-19 vaccines in Japan

“…For both the BNT162b2 and mRNA-1273 vaccines, almost all systemic reactions were significantly more frequent in females than in males, in the younger age group (<50 years) than in the older age group (≥50 years), and after the second dose. These results are generally consistent with the results of previous studies [ 3 , 4 , 7 , 9 , 10 ]. In contrast, there were no significant difference in the incidence of injection site pain with either vaccine between first and second dose.…”

“…The most severe and most frequent systemic adverse reaction was fatigue, with both the BNT162b2 and the mRNA-1273 vaccines. The incidence of absenteeism following the BNT162b2 vaccine is consistent with that of a previous study from Japan [ 7 ]. The frequency of reported reactions is generally consistent with the results observed in previous studies [ 3 , 4 , 7 , 9 , 10 ].…”

“…The incidence of absenteeism following the BNT162b2 vaccine is consistent with that of a previous study from Japan [ 7 ]. The frequency of reported reactions is generally consistent with the results observed in previous studies [ 3 , 4 , 7 , 9 , 10 ]. In this study, injection site pain was the most common adverse reaction after both the first and second doses of both vaccines.…”

“…In this study, injection site pain was the most common adverse reaction after both the first and second doses of both vaccines. The incidence of injection site pain in this study was higher than that reported in previous large studies conducted in the US and UK [ 9 , 10 ], but similar to that of a previous study conducted in Japan [ 7 ]. The differences in the reported incidence of injection site pain between studies may be because the participants in this study were younger than those of previous studies conducted in the US and UK [ 3 , 4 , 9 ].…”

“…Therefore, continued monitoring of adverse reactions to COVID-19 vaccines under programmatic conditions, especially in young age groups, may provide relevant information to the public and contribute to people's acceptance of COVID-19 vaccines. However, programmatic evidence on the reactogenicity of COVID-19 vaccines in the Japanese population is limited [ 6 , 7 ]. In addition, there is a lack of evidence on the comparative side effects of different COVID-19 vaccines.…”