Safety and immunogenicity of intramuscular, single-dose V590 (rVSV-SARS-CoV-2 Vaccine) in healthy adults: Results from a phase 1 randomised, double-blind, placebo-controlled, dose-ranging trial.

BACKGROUND: Vaccines against COVID-19 are needed to overcome challenges associated with mitigating the global pandemic. We report the safety and immunogenicity of V590, a live recombinant vesicular stomatitis virus-based COVID-19 vaccine candidate. METHODS: In this placebo-controlled, double-blind, three-part phase 1 study, healthy adults were randomised to receive a single intramuscular dose of vaccine or placebo. In Part 1, younger (18-54 years) and, in Part 2, older (≥55 years) adults seronegative for SARS-CoV-2 nucleocapsid received one of four V590 dose levels (5.00 × 105; 2.40 × 106; 1.15 × 107; or 5.55 × 107 plaque-forming units [pfu]) or placebo. In Part 3, a single V590 dose level (5.55 × 107 pfu) or placebo was administered to younger SARS-CoV-2 seropositive adults. Primary endpoints included adverse events (AEs) and for Parts 1 and 2 anti-SARS-CoV-2 serum neutralising antibody responses measured by 50% plaque reduction neutralisation (PRNT50) assay at Day 28. Registration NCT04569786 [P001-02]. FINDINGS: 232 participants were randomised and 219 completed the study. In seronegative participants, anti-SARS-CoV-2 spike-specific antibody responses to V590 were low and comparable to placebo across the lower dose levels. At the highest dose level (5.55 × 107 pfu), anti-SARS-CoV-2 spike-specific PRNT50 was 2.3-fold higher than placebo. The most frequently reported AEs were injection-site pain (38.4%), headache (15.1%) and fatigue (13.4%). INTERPRETATION: V590 was generally well-tolerated. However, Day 28 anti-SARS-Cov-2 spike-specific antibody responses in seronegative participants following a single intramuscular administration of V590 were not sufficient to warrant continued development. FUNDING: The study was funded by Merck Sharp & Dohme LLC., a subsidiary of Merck & Co., Inc., Rahway, NJ, USA.

Safety and immunogenicity of the measles vector-based SARS-CoV-2 vaccine candidate, V591, in adults: results from a phase 1/2 randomised, double-blind, placebo-controlled, dose-ranging trial.

BACKGROUND: We report on the safety and immunogenicity of V591, a measles vector-based SARS-CoV-2 vaccine candidate. METHODS: In this multicentre, randomised, placebo-controlled, double-blind, phase 1/2 trial, healthy adults with no history of COVID-19 disease were assigned to intramuscular injection of V591 or placebo (4:1 ratio). In part 1, younger adults (18-55 years) received V591 median tissue culture infectious dose (TCID50)-levels of 1×105 or 1×106 or placebo, 56 days apart. In part 2, younger and older (>55 years) adults received a single dose of one of four (104/105/106/107) or one of two (105/106) V591 TCID50 levels, respectively, or placebo. PRIMARY OUTCOME: safety/tolerability. Secondary outcome: humoral immunogenicity. ClinicalTrials.gov: NCT04498247. FINDINGS: From August-December 2020, 444 participants were screened and 263 randomised (210 V591; 53 placebo); 262 received at least one and 10 received two doses of V591 or placebo. Adverse events were experienced by 140/209 (67.0%) V591 dose-group participants and 37/53 (69.8%) placebo-group participants following injection 1; most frequent were fatigue (57 [27.3%] vs 20 [37.7%]), headache (57 [27.3%] vs 19 [35.8%]), myalgia (35 [16.7%] vs 10 [18.9%]), and injection-site pain (35 [16.7%] vs 4 [7.5%]). No deaths nor vaccine-related serious adverse events occurred. At Day 29, no anti-SARS-CoV-2 spike serum neutralising antibody and IgG-responses were identified in placebo or the three lower V591 dose-groups; responses were detected with V591 1×107 TCID50, although titres were lower than convalescent serum. INTERPRETATION: V591 was generally well tolerated, but immunogenicity was insufficient to warrant continued development. FUNDING: Merck Sharp & Dohme, Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA.

A phase 1, randomized, placebo-controlled study to evaluate the safety and immunogenicity of an mRNA-based RSV prefusion F protein vaccine in healthy younger and older adults.

Respiratory Syncytial Virus (RSV) causes lower respiratory tract infections that can be severe and sometimes fatal. The risk for severe RSV infection is highest in infants and older adults. A safe and effective RSV vaccine for older adults represents a serious unmet medical need due to higher morbidity and mortality in this age group. In this randomized, partially double-blind, placebo-controlled, phase 1 dose-escalation study, we evaluated the safety, tolerability and immunogenicity of an investigational messenger ribonucleic acid (mRNA) vaccine encoding the RSV fusion protein (F) stabilized in the prefusion conformation. The study was conducted in healthy younger adults (ages ≥18 and ≤49 years) and healthy older adults (ages ≥60 and ≤79 years). Participants received mRNA-1777 (V171) or placebo as a single intramuscular dose. For each dose level, three sentinel participants were administered open-label mRNA-1777 (V171). Seventy-two younger adults were randomized and administered 25, 100, or 200 µg mRNA-1777 (V171) or placebo, and 107 older adults were randomized and administered 25, 100, 200 or 300 µg mRNA-1777 (V171) or placebo. Primary objectives were safety and tolerability and secondary objectives included humoral and cell-mediated immunogenicity. All dose levels of mRNA-1777 (V171) were generally well tolerated and no serious adverse events related to the vaccine were reported. Immunization with mRNA-1777 (V171) elicited a humoral immune response as measured by increases in RSV neutralizing antibody titers, serum antibody titers to RSV prefusion F protein, D25 competing antibody titers to RSV prefusion F protein, and cell-mediated immune responses to RSV-F peptides.