Background Few data exist on the comparative safety and immunogenicity of different
COVID-19 vaccines given as a third (booster) dose. To generate data to optimise selection …

Background Some high-income countries have deployed fourth doses of COVID-19
vaccines, but the clinical need, effectiveness, timing, and dose of a fourth dose remain …

Background A new variant of SARS-CoV-2, B. 1.1. 7, emerged as the dominant cause of
COVID-19 disease in the UK from November, 2020. We report a post-hoc analysis of the …

Background The pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-
2) might be curtailed by vaccination. We assessed the safety, reactogenicity, and …

Background To date, no immunological data on COVID-19 heterologous vaccination
schedules in humans have been reported. We assessed the immunogenicity and …

Background Heterologous vaccine regimens have been widely discussed as a way to
mitigate intermittent supply shortages and to improve immunogenicity and safety of COVID …

Background Vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-
2), the virus that causes coronavirus disease 2019 (Covid-19), have been used since …

Background COVID-19 vaccine supply shortages are causing concerns about compromised
immunity in some countries as the interval between the first and second dose becomes …

Objectives To evaluate the persistence of immunogenicity three months after third dose
boosters. Methods COV-BOOST is a multicentre, randomised, controlled, phase 2 trial of …

Background The safety and efficacy of the AZD1222 (ChAdOx1 nCoV-19) vaccine in a large,
diverse population at increased risk for severe acute respiratory syndrome coronavirus 2 …