Safety and Immunogenicity of an Inactivated Recombinant Newcastle Disease Virus Vaccine Expressing SARS-CoV-2 Spike: Interim Results of a Randomised, Placebo-Controlled, Phase 1/2 Trial

BackgroundProduction of affordable coronavirus disease 2019 (COVID-19) vaccines in low- and middle-income countries is needed. NDV-HXP-S is an inactivated egg-based Newcastle disease virus vaccine expressing the spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Its being developed in Thailand, Vietnam, and Brazil; herein are initial results from Thailand. MethodsThis phase 1 stage of a randomised, dose-escalation, observer-blind, placebo-controlled, phase 1/2 trial was conducted at the Vaccine Trial Centre, Mahidol University (Bangkok). Healthy adults aged 18-59 years, non-pregnant and negative for SARS-CoV-2 antibodies were eligible. Participants were block randomised to receive one of six treatments by intramuscular injection twice, 28 days apart: 1 {micro}g{+/-}CpG1018 (a toll-like receptor 9 agonist), 3 {micro}g{+/-}CpG1018, 10 {micro}g, or placebo. Participants and personnel assessing outcomes were masked to treatment. The primary outcomes were solicited and spontaneously reported adverse events (AEs) during 7 and 28 days after each vaccination, respectively. Secondary outcomes were immunogenicity measures (anti-S IgG and pseudotyped virus neutralisation). An interim analysis assessed safety at day 57 in treatment-exposed individuals and immunogenicity through day 43 per protocol. ClinicalTrials.gov (NCT04764422). FindingsBetween March 20 and April 23, 2021, 377 individuals were screened and 210 were enrolled (35 per group); all received dose one; five missed dose two. The most common solicited AEs among vaccinees, all predominantly mild, were injection site pain (<63%), fatigue (<35%), headache (<32%), and myalgia (<32%). The proportion reporting a vaccine-related AE ranged from 5{middle dot}7% to 17{middle dot}1% among vaccine groups and was 2{middle dot}9% in controls; there was no vaccine-related serious adverse event. The 10 {micro}g formulations immunogenicity ranked best, followed by 3 {micro}g+CpG1018, 3 {micro}g, 1 {micro}g+CpG1018, and 1 {micro}g formulations. On day 43, the geometric mean concentrations of 50% neutralising antibody ranged from 122{middle dot}23 IU/mL (1 {micro}g, 95% CI 86{middle dot}40-172{middle dot}91) to 474{middle dot}35 IU/mL (10 {micro}g, 95% CI 320{middle dot}90-701{middle dot}19), with 93{middle dot}9% to 100% of vaccine groups attaining a [≥]4-fold increase over baseline. InterpretationNDV-HXP-S had an acceptable safety profile and potent immunogenicity. The 3 {micro}g and 3 {micro}g+CpG1018 formulations advanced to phase 2. FundingNational Vaccine Institute (Thailand), National Research Council (Thailand), Bill & Melinda Gates Foundation, National Institutes of Health (USA)