Bivalent BNT162b2mRNA original/Omicron BA.4-5 booster vaccination: adverse reactions and inability to work compared to the monovalent COVID-19 booster

In the light of emerging SARS-CoV-2 variants of concern (VOC), bivalent COVID-19 vaccines combining the wild-type spike mRNA with an Omicron VOC BA.1 or BA.4-5 spike mRNA became available. This non-randomized controlled study examined adverse reactions, PRN ( pro re nata ) medication intake and inability to work after a fourth COVID-19 vaccination among 76 healthcare workers. As fourth dose either the original, monovalent BNT162b2mRNA (48.7%) or the bivalent BNT162b2mRNA original/Omicron BA.4-5 vaccine (51.3%) was administered. The rate of adverse reactions for the second booster dose was significantly higher among participants receiving the bivalent 84.6% (95% CI 70.3%-92.8%; 33/39) compared to the monovalent 51.4% (95% CI 35.9-66.6%; 19/37) vaccine (p=0.0028). Also, there was a trend towards an increased rate of inability to work and intake of PRN medication following bivalent vaccination. In view of preprints reporting inconclusive results in neutralizing antibody levels between the compared vaccines, our results and further studies on safety and reactogenicity of bivalent COVID-19 booster vaccines are highly important to aid clinical decision making in the choice between bivalent and monovalent vaccinations.