Project description:SARS-CoV-2 reinfections increased substantially after Omicron variants emerged. Large-scale community-based comparisons across multiple Omicron waves of reinfection characteristics, risk factors, and protection afforded by previous infection and vaccination, are limited. Here we studied ~45,000 reinfections from the UK's national COVID-19 Infection Survey and quantified the risk of reinfection in multiple waves, including those driven by BA.1, BA.2, BA.4/5, and BQ.1/CH.1.1/XBB.1.5 variants. Reinfections were associated with lower viral load and lower percentages of self-reporting symptoms compared with first infections. Across multiple Omicron waves, estimated protection against reinfection was significantly higher in those previously infected with more recent than earlier variants, even at the same time from previous infection. Estimated protection against Omicron reinfections decreased over time from the most recent infection if this was the previous or penultimate variant (generally within the preceding year). Those 14-180 days after receiving their most recent vaccination had a lower risk of reinfection than those >180 days from their most recent vaccination. Reinfection risk was independently higher in those aged 30-45 years, and with either low or high viral load in their most recent previous infection. Overall, the risk of Omicron reinfection is high, but with lower severity than first infections; both viral evolution and waning immunity are independently associated with reinfection.
Project description:Mucosal immunity plays a pivotal role in providing comprehensive protection against upper-airway infections and effectively limiting the shedding and transmission of SARS-CoV-2. Despite its critical importance, there remains a notable absence of nasal spray vaccines endorsed for global use by the World Health Organization. This could be due to the inability of current intranasal vaccines to induce strong mucosal and systemic responses in humans, thus urgently entailing a next-generation of intranasal COVID-19 vaccines with novel and safe technologies. In this study, we prepared a two-component intranasal vaccine that combines adenovirus vectors with a self-assembled subunit protein. Specifically, the adenovirus vector expresses the spike protein of XBB.1.5 variant (Ad5XBB.1.5), and were mixed with the recombinant protein that developed derived from the receptor binding domain (RBD) of XBB.1.5 (RBDXBB.1.5-HR). Combination of Ad5XBB.1.5 and RBDXBB.1.5-HR elicited superior humoral and cellular immunity against XBB.1.5-included variants compared with the individual components. Importantly, the STING signaling pathway was found to be crucial for the adjuvant effect of the adenovirus vector. In addition, to increase the broad-spectrum neutralizing capacities, a trimeric protein derived from the BA.5 variant (RBDBA.5-HR) was incorporated to formulate a three-component vaccine (Ad5XBB.1.5+RBDXBB.1.5-HR+RBDBA.5-HR), indicating the utilization of a combination of an adenovirus-vectored and subunit protein vaccines has the potential to serve as a next-generation intranasal vaccine platform. Of note, intranasally delivery of two-component vaccine provided protective immunity against live Omicron XBB.1.16 virus challenge in mice. Furthermore, the combination of adenovirus and subunit protein vaccine demonstrates excellent tolerability and safety in human subjects, and is able to induce enhanced mucosal immunity as well as high levels of sera neutralizing antibody in all participants. These findings underscore its suitability for clinical application in the prevention of SARS-CoV-2 variants encompassing XBB lineages.
Project description:We generated LNP-mRNA encoding B.1.1.529 SARS-CoV-2 spike, and intramuscularly administered it in a human IgG and IgK knock-in mouse. Single cell VDJ-seq unveiled the sequences of human monoclonal antibodies targeting the B.1.1.529 SARS-CoV-2 spike protein.