Abstract：
COVID-19 vaccine boosters may optimize durability of protection against variants of concern (VOCs). In this randomized, double-blind, phase 2 trial, participants received 3 different dose levels of an Ad26.COV2.S booster (5 × 1010 vp [viral particles], 2.5 × 1010 vp, or 1 × 1010 vp) ≥6 months post-primary vaccination with either single-dose Ad26.COV2.S (homologous boost; n = 774) or 2-dose BNT162b2 (heterologous boost; n = 758). Primary endpoints were noninferiority of neutralizing antibody responses at Day 15 post-boost versus Day 29 post-primary vaccination. Secondary endpoints included reactogenicity/safety and neutralizing antibody responses to VOCs. All primary endpoints passed prespecified hierarchical noninferiority criteria by Day 15 post-boost. Geometric mean increases in neutralizing antibody titers against the D614G reference strain ranged from 5.5 to 6.8 at Day 15 for homologous boosting and 12.6 to 22.0 for heterologous boosting. For VOCs, heterologous boosting elicited higher neutralizing antibody responses than homologous boosting. Neutralizing antibody responses were dose-dependent and durable for ≥6 months post-boost. More solicited systemic adverse events occurred following heterologous versus homologous boosting. Trial Registration:ClinicalTrials.gov Identifier: NCT04999111.
摘要：
COVID-19疫苗增强剂可能会优化针对关注变种（VOC）的保护作用的持久性。在这个随机的，双盲,第二阶段试验，参与者接受了3种不同剂量水平的Ad26.COV2.S助推器(5×1010vp[病毒颗粒]，2.5×1010vp,或1×1010vp）在初次接种单剂量Ad26后≥6个月。COV2.S(同源加强;n=774)或2剂量BNT162b2(异源加强;n=758)。主要终点是加强后第15天相对于初次疫苗接种后第29天的中和抗体应答的非劣效性。次要终点包括反应原性/安全性和对VOC的中和抗体应答。到加强后第15天，所有主要终点均通过了预设的等级非劣效性标准。针对D614G参考菌株的中和抗体滴度的几何平均增加在第15天对于同源加强为5.5至6.8,对于异源加强为12.6至22.0。对于VOCs，异源加强比同源加强引起更高的中和抗体应答。中和抗体反应是剂量依赖性的，并且在加强后持续≥6个月。异源与同源加强后发生了更多的系统性不良事件。试用注册：ClinicalTrials.gov标识符：NCT04999111。
