Prospective Monitoring of BNT162b2 Second Vaccination Booster Effects in Health Care Workers (HCW)

The SARS-CoV-2 virus causes severe respiratory illness and is an ongoing global pandemic. On December 12, 2020 the FDA approved Pfizer's BioNTech vaccine BNT162b2 which is a messenger RNA type of vaccine for use. This vaccine has shown in numerous studies the ability to induce a strong immune response and provide both humeral and cellular protection against wild type, alpha and delta variants of SARS-CoV2 virus. In Israel the national vaccine operation began in mid-December 2020 which included 2 initial doses three weeks apart. In August 2021 a first booster (3rd dose) was provided to enhance protection and due to reports of reduced immune response and clinical protection. Several studies have demonstrated that over time there is a decay in the antibody levels, and with them reduced protection. Recently a new variant of concern has been identified (Omicron) and is causing a surge of infections worldwide. There is lack of knowledge regarding the effectiveness of the current schedule of vaccine against this new variant and whether a second booster (4th dose) will provide higher levels of clinical protection against this variant, currently the ministry of health is considering recommendations for a fourth dose for HCW. The purpose of this study is to examine whether a fourth dose of vaccination will provide better protection against infection and clinical disease.