Anat Achiron*, Mathilda Mandel, David Magalashvili, Sapir Dreyer-Alster, Polina Sonis, Rina Falb, Michael Gurevich
We evaluated adaptive immune responses in three-time BNT162b2 mRNA vaccinated individuals that subsequently developed Omicron Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) breakthrough infections. Following the third mRNA booster, all subjects had protective IgG antibody response and memory B and T cells responses. However, these responses were not sufficient to prevent Omicron infection that occurred within a period of few months following the booster dose. Our findings suggest the need for a targeted vaccine against Omicron.