Booster vaccination using bivalent DS-5670a/b is safe and immunogenic against SARS-CoV-2 variants in children aged 5–11 years: a phase 2/3, randomized, active-controlled study oleh Rino Suzuki, Miharu Suda, Katsuyasu Ishida, Kei Furihata, Aisaku Ota, Kaori Takahashi, Sachiko Sakakibara, Tetsuo Nakayama, Fumihiko Takeshita