Immunogenicity and safety of boosting with a recombinant two-component SARS-CoV-2 vaccine: two randomized, parallel-controlled, phase 2 studies.

BACKGROUND: Recombinant protein vaccines are vital for broad protection against SARS-CoV-2 variants. This study assessed ReCOV as a booster in two Phase 2 trials. RESEARCH DESIGN AND METHODS: Study-1 involved subjects were randomized (1:1:1) to receive 20 µg ReCOV, 40 µg ReCOV, or an inactivated vaccine (COVILO®) in the United Arab Emirates. Study-2 participating individuals were randomized (1:1:1) to receive 20 µg ReCOV (pilot batch, ReCOV HA), 20 µg ReCOV (commercial batch, ReCOV TC), or 30 µg BNT162b2 (COMIRNATY®) in the Philippines. The primary immunogenicity objectives was to compare the geometric mean titer (GMT) and seroconversion rate (SCR) of neutralizing antibodies induced by one ReCOV booster dose with those of inactivated vaccine and BNT162b2, respectively, at 14 days post-booster. RESULTS: Heterologous ReCOV booster doses were safe and induced comparable immune responses to inactivated vaccines and BNT162b2 against Omicron variants and the prototype. They showed significant advantages in cross-neutralization against multiple SARS-CoV-2 variants, surpassing inactivated vaccines and BNT162b2, with good immune persistence. CONCLUSIONS: Heterologous ReCOV boosting was safe and effective, showing promise in combating COVID-19. The study highlights ReCOV's potential for enhanced protection, supported by strong cross-neutralization and immune persistence. CLINICAL TRIAL REGISTRATION: Study-1, www.clinicaltrials.gov, identifier is NCT05323435; Study-2, www.clinicaltrials.gov, identifier is NCT05084989.

Safety and Immunogenicity of a Recombinant Two-Component SARS-CoV-2 Protein Vaccine: Randomized, Double-Blind, Placebo-Controlled Phase I and Phase II Studies.

INTRODUCTION: ReCOV is a recombinant protein vaccine that aims to induce cross-neutralization against SARS-CoV-2 variants. The phase I and phase II studies were conducted in New Zealand and the Philippines, respectively, for ReCOV primary series. METHODS: Both studies were randomized, double-blind, placebo-controlled designed among COVID-19 vaccine-naïve healthy adults who received two doses of study vaccination with a 21-day interval. In phase I, 100 younger (15-55 years) and older (56-80 years) subjects were 4:1 randomized to receive ReCOV (20 µg or 40 µg) or placebo. In the phase II study, 347 subjects (≥ 18 years) were 2:1 randomized to receive 40 µg ReCOV or placebo. Subjects that received ReCOV were followed up for 6 months after the second dosing. The safety outcomes included solicited and unsolicited AEs, SAEs, and AESIs. The immunogenicity outcomes were live-virus neutralizing antibody (NAb) against prototype, while pseudovirus NAbs against several SARS-CoV-2 variants were included in phase II as well. RESULTS: No related SAE, AESI, or AE leading to early discontinuation were reported. The AE incidences were higher in ReCOV groups than placebo group in phase I while they were similar between study groups in phase II. The majority of solicited AEs were mild or moderate with median duration of 1.0-4.0 days. The common (≥ 10%) solicited AEs in phase I were injection site reactions, headache, pyrexia, fatigue, and myalgia, and common reported (≥ 5%) ones in phase II included injection site pain, headache, and pyrexia. Robust neutralizing activities against the prototype were observed in ReCOV groups, peaking at 14 days post the second dosing: in phase I, the GMTs for 20 µg and 40 µg ReCOV groups were 1643.2 IU/mL (95% CI 1188.5, 2271.9) and 1289.2 IU/mL (95% CI 868.3, 1914.1) in younger adults, and 1122.3 IU/mL (95% CI 722.6, 1743.1) and 680.3 IU/mL (95% CI 440.2, 1051.4) in older adults, respectively, while in the ReCOV group of phase II, the GMTs for subjects with seronegative and seropositive status at baseline were 3741.0 IU/mL (95% CI 3113.4, 4495.0) and 6138.3 IU/mL (95% CI 5255.1, 7169.9), respectively. In phase II, substantial levels of pseudovirus NAbs against SARS-CoV-2 variants were demonstrated; the peak GMTs for prototype, Omicron BA.2, and BA.4/5 were 8857, 4441, and 2644, and 15,667.3, 7334.3, and 4478.8 among seronegative and seropositive subjects, respectively. The neutralization persisted till 6 months post the second dosing, with only 2.5- to 5.2-fold declines for Omicron variants. CONCLUSIONS: Two doses of 20 µg and 40 µg ReCOV are safe and immunogenic against SARS-CoV-2 prototype. The cross-neutralizing activities against Omicron variants support ReCOV advance to late-stage clinical trials. TRIAL REGISTRATION: Phase I study, clinicaltrials.gov NCT04818801; phase II study, clinicaltrials.gov NCT05084989.

Safety and efficacy of the intranasal spray SARS-CoV-2 vaccine dNS1-RBD: a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial.

BACKGROUND: The live-attenuated influenza virus vector-based intranasal SARS-CoV-2 vaccine (dNS1-RBD, Pneucolin; Beijing Wantai Biological Pharmacy Enterprise, Beijing, China) confers long-lasting and broad protection in animal models and is, to our knowledge, the first COVID-19 mucosal vaccine to enter into human trials, but its efficacy is still unknown. We aimed to assess the safety and efficacy (but not the immunogenicity) of dNS1-RBD against COVID-19. METHODS: We did a multicentre, randomised, double-blind, placebo-controlled, adaptive design, phase 3 trial at 33 centres (private or public hospitals, clinical research centres, or Centre for Disease Control and Prevention) in four countries (Colombia, Philippines, South Africa, and Viet Nam). Men and non-pregnant women (aged ≥18 years) were eligible if they had never been infected with SARS-CoV-2, and if they did not have a SARS-CoV-2 vaccination history at screening or if they had received at least one dose of other SARS-CoV-2 vaccines 6 months or longer before enrolment. Eligible adults were randomly assigned (1:1) to receive two intranasal doses of dNS1-RBD or placebo administered 14 days apart (0·2 mL per dose; 0·1 mL per nasal cavity), with block randomisation via an interactive web-response system, stratified by centre, age group (18-59 years or ≥60 years), and SARS-CoV-2 vaccination history. All participants, investigators, and laboratory staff were masked to treatment allocation. The primary outcomes were safety of dNS1-RBD in the safety population (ie, those who had received at least one dose of dNS1-RBD or placebo) and efficacy against symptomatic SARS-CoV-2 infection confirmed by RT-PCR occurring 15 days or longer after the second dose in the per-protocol population (ie, those who received two doses, were followed up for 15 days or longer after the second dose, and had no major protocol deviations). The success criterion was predefined as vaccine efficacy of more than 30%. This trial is registered with the Chinese Clinical Trial Registry (ChiCTR2100051391) and is completed. FINDINGS: Between Dec 16, 2021, and May 31, 2022, 41 620 participants were screened for eligibility and 31 038 participants were enrolled and randomly assigned (15 517 in the vaccine group and 15 521 in the placebo group). 30 990 participants who received at least one dose (15 496 vaccine and 15 494 placebo) were included in the safety analysis. The results showed a favourable safety profile, with the most common local adverse reaction being rhinorrhoea (578 [3·7%] of 15 500 vaccine recipients and 546 [3·5%] of 15 490 placebo recipients) and the most common systemic reaction being headache (829 [5·3%] vaccine recipients and 797 [5·1%] placebo recipients). We found no differences in the incidences of adverse reactions between participants in the vaccine and placebo groups. No vaccination-related serious adverse events or deaths were observed. Among 30 290 participants who received two doses, 25 742 were included in the per-protocol efficacy analysis (12 840 vaccine and 12 902 placebo). The incidence of confirmed symptomatic SARS-CoV-2 infection caused by omicron variants regardless of immunisation history was 1·6% in the vaccine group and 2·3% in the placebo group, resulting in an overall vaccine efficacy of 28·2% (95% CI 3·4-46·6), with a median follow-up duration of 161 days. INTERPRETATION: Although this trial did not meet the predefined efficacy criteria for success, dNS1-RBD was well tolerated and protective against omicron variants, both as a primary immunisation and as a heterologous booster. FUNDING: Beijing Wantai Biological Pharmacy Enterprise, National Science and Technology Major Project, National Natural Science Foundation of China, Fujian Provincial Science and Technology Plan Project, Natural Science Foundation of Fujian Province, Xiamen Science and Technology Plan Special Project, Bill & Melinda Gates Foundation, the Ministry of Education of China, Xiamen University, and Fieldwork Funds of Xiamen University.