High neutralizing activity against Omicron BA.2 can be induced by COVID-19 mRNA booster vaccination

The VOC of SARS-CoV-2, Omicron (BA.1, BA.1.1, BA.2, or BA.3), is associated with an increased risk of reinfection. BA.2 has become the next dominant variant worldwide. Although BA.2 infection has been shown to be mild illness, its high transmissibility will result in high numbers of cases. In response to the surge of Omicron BA.1 cases, booster vaccination was initiated in many countries. But there is limited evidence regarding the effectiveness of a booster vaccination against BA.2. We collected blood samples from 84 physicians at Kobe University Hospital, Japan, in January 2022 ∼7 months after they had received two BNT162b2 vaccinations and ∼2 weeks after their booster vaccination. We performed a serum neutralizing assay against BA.2 using authentic virus.

Although most of the participants had no or a very low titer of neutralizing antibody against BA.2 at 7 months after two BNT162b2 vaccinations, the titer increased significantly at 2 weeks after the booster vaccination.