Immunogenicity and Vaccine Shedding After 1 or 2 Doses of rVSVΔG-ZEBOV-GP Ebola Vaccine (ERVEBO®): Results From a Phase 2, Randomized, Placebo-controlled Trial in Children and Adults.

BACKGROUND: The rVSVΔG-ZEBOV-GP vaccine (ERVEBO®) is a single-dose, live-attenuated, recombinant vesicular stomatitis virus vaccine indicated for the prevention of Ebola virus disease (EVD) caused by Zaire ebolavirus in individuals 12 months of age and older. METHODS: The Partnership for Research on Ebola VACcination (PREVAC) is a multicenter, phase 2, randomized, double-blind, placebo-controlled trial of 3 vaccine strategies in healthy children (ages 1-17) and adults, with projected 5 years of follow-up (NCT02876328). Using validated assays (GP-ELISA and PRNT), we measured antibody responses after 1-dose rVSVΔG-ZEBOV-GP, 2-dose rVSVΔG-ZEBOV-GP (given on Day 0 and Day 56), or placebo. Furthermore, we quantified vaccine virus shedding in a subset of children's saliva using RT-PCR. RESULTS: In total, 819 children and 783 adults were randomized to receive rVSVΔG-ZEBOV-GP (1 or 2 doses) or placebo. A single dose of rVSVΔG-ZEBOV-GP increased antibody responses by Day 28 that were sustained through Month 12. A second dose of rVSVΔG-ZEBOV-GP given on Day 56 transiently boosted antibody concentrations. In vaccinated children, GP-ELISA titers were superior to placebo and non-inferior to vaccinated adults. Vaccine virus shedding was observed in 31.7% of children, peaking by Day 7, with no shedding observed after Day 28 post-dose 1 or any time post-dose 2. CONCLUSIONS: A single dose of rVSVΔG-ZEBOV-GP induced robust antibody responses in children that was non-inferior to the responses induced in vaccinated adults. Vaccine virus shedding in children was time-limited and only observed after the first dose. Overall, these data support the use of rVSVΔG-ZEBOV-GP for the prevention of EVD in at-risk children. Clinical Trials Registration. The study is registered at ClinicalTrials.gov (NCT02876328), the Pan African Clinical Trials Registry (PACTR201712002760250), and the European Clinical Trials Register (EudraCT number: 2017-001798-18).

Development of Pandemic Vaccines: ERVEBO Case Study.

Preventative vaccines are considered one of the most cost-effective and efficient means to contain outbreaks and prevent pandemics. However, the requirements to gain licensure and manufacture a vaccine for human use are complex, costly, and time-consuming. The 2013-2016 Ebola virus disease (EVD) outbreak was the largest EVD outbreak to date and the third Public Health Emergency of International Concern in history, so to prevent a pandemic, numerous partners from the public and private sectors combined efforts and resources to develop an investigational Zaire ebolavirus (EBOV) vaccine candidate (rVSVΔG-ZEBOV-GP) as quickly as possible. The rVSVΔG-ZEBOV-GP vaccine was approved as ERVEBOTM by the European Medicines Authority (EMA) and the United States Food and Drug Administration (FDA) in December 2019 after five years of development. This review describes the development program of this EBOV vaccine, summarizes what is known about safety, immunogenicity, and efficacy, describes ongoing work in the program, and highlights learnings applicable to the development of pandemic vaccines.

Immunogenicity, Lot Consistency, and Extended Safety of rVSVΔG-ZEBOV-GP Vaccine: A Phase 3 Randomized, Double-Blind, Placebo-Controlled Study in Healthy Adults.

BACKGROUND: This double-blind study assessed immunogenicity, lot consistency, and safety of recombinant vesicular stomatitis virus-Zaire Ebola virus envelope glycoprotein vaccine (rVSVΔG-ZEBOV-GP). METHODS: Healthy adults (N = 1197) were randomized 2:2:2:2:1 to receive 1 of 3 consistency lots of rVSVΔG-ZEBOV-GP (2 × 107 plaque-forming units [pfu]), high-dose 1 × 108 pfu, or placebo. Antibody responses pre-/postvaccination (28 days, 6 months; in a subset [n = 566], months 12, 18, and 24) were measured. post hoc analysis of risk factors associated with arthritis following vaccination was performed. RESULTS: ZEBOV-GP enzyme-linked immunosorbent assay (ELISA) geometric mean titers (GMTs) increased postvaccination in all rVSVΔG-ZEBOV-GP groups by 28 days (>58-fold) and persisted through 24 months. The 3 manufacturing lots demonstrated equivalent immunogenicity at 28 days. Neutralizing antibody GMTs increased by 28 days in all rVSVΔG-ZEBOV-GP groups, peaking at 18 months with no decrease through 24 months. At 28 days, ≥94% of vaccine recipients seroresponded (ZEBOV-GP ELISA, ≥2-fold increase, titer ≥200 EU/mL), with responses persisting at 24 months in ≥91%. Female sex and a history of arthritis were identified as potential risk factors for the development of arthritis postvaccination. CONCLUSIONS: Immune responses to rVSVΔG-ZEBOV-GP persisted to 24 months. Immunogenicity and safety results support continued rVSVΔG-ZEBOV-GP development. CLINICAL TRIALS REGISTRATION: NCT02503202.

Six-Month Safety Data of Recombinant Vesicular Stomatitis Virus-Zaire Ebola Virus Envelope Glycoprotein Vaccine in a Phase 3 Double-Blind, Placebo-Controlled Randomized Study in Healthy Adults.

Background: This study (NCT02503202) evaluated the safety of recombinant vesicular stomatitis virus-Zaire Ebola virus envelope glycoprotein vaccine (rVSVΔG-ZEBOV-GP). Methods: Overall, 1197 subjects were randomized 2:2:2:2:1; 1194 were vaccinated with 1 dose of 1 of 3 lots of rVSVΔG- ZEBOV-GP (2 × 107 plaque-forming units [pfu], n = 797; combined-lots group), a single high-dose lot of rVSVΔG-ZEBOV-GP (1 × 108 pfu, n = 264; high-dose group), or placebo (n = 133). Daily temperatures and adverse events (AEs) were recorded days 1 to 42 postvaccination. Solicited AEs included injection-site AEs from days 1 to 5, and joint pain, joint swelling, vesicular lesions (blisters), and rashes from days 1 to 42. Serious AEs (SAEs) were recorded through 6 months postvaccination. Results: Fever (≥38.0°C) was observed in 20.2% of combined lots (3.2% with ≥39.0°C), 32.2% of high-dose (4.3% with ≥39.0°C), and 0.8% of placebo (0.8% with ≥39.0°C). Incidences of AEs of interest (days 1-42) were arthralgia (17.1% combined lots, 20.4% high-dose, 3.0% placebo), arthritis (5.1% combined lots, 4.2% high-dose, 0.0% placebo), and rash (3.8% combined lots, 3.8% high-dose, 1.5% placebo). Twenty-one SAEs and 2 deaths were reported, all assessed by investigators as unrelated to vaccine. Conclusions: rVSVΔG-ZEBOV-GP was generally well-tolerated, with increased rates of injection-site and systemic AEs compared to placebo, and no vaccine-related SAEs or deaths. These findings support the use of rVSVΔG-ZEBOV-GP vaccine in persons at risk for Ebola virus disease. Clinical Trials Registration: NCT02503202.

Staphylococcus aureus Infections After Elective Cardiothoracic Surgery: Observations From an International Randomized Placebo-Controlled Trial of an Investigational S aureus Vaccine.

BACKGROUND: An unmet need to prevent Staphylococcus aureus (SA) infections after cardiothoracic surgery persists despite current practices. Cost-effective implementation of preventive strategies requires contemporary knowledge about modifiable risk factors. METHODS: From 2007 to 2011, an international, double-blind, randomized placebo-controlled trial of a novel SA vaccine (V710) was conducted in 7664 adults scheduled for median sternotomy at 164 sites. We analyzed SA infections developing up to 360 days postoperatively in 3832 placebo recipients. RESULTS: Coronary artery bypass grafting was performed in 80.8% (3096 of 3832) of placebo recipients. The overall incidence of any postoperative SA infection was 3.1% (120 of 3832). Invasive SA infections (including bacteremia and deep sternal-wound infections) developed in 1.0%. Methicillin-resistant SA (MRSA) accounted for 19% (23 of 120) of SA infections, with 57% (13 of 23) of the MRSA infections occurring in diabetic patients. All-cause mortality was 4.1% (153 of 3712) in patients without SA infection, 7.2% (7 of 97) in methicillin-susceptible SA (MSSA) infections, and 17.3% (4 of 23) in MRSA infections (P < .01). Staphylococcus aureus nasal carriage was detected preoperatively in 18.3% (701 of 3096) patients, including 1.6% colonized with MRSA. Postoperative SA infections occurred in 7.0% (49 of 701) of colonized patients versus 2.3% (71 of 3131) of patients without colonization (relative risk = 3.1 [95% confidence interval, 2.2-4.4]). CONCLUSIONS: In this large international cohort of patients undergoing cardiac surgery and observed prospectively, invasive postoperative SA infections occurred in 1% of adult patients despite modern perioperative management. The attributable mortality rates were 3% for MSSA and 13% for MRSA infections. Preoperative nasal colonization with SA increased the risk of postoperative infection threefold. The utility of strategies to reduce this incidence warrants continued investigation.

Effect of an investigational vaccine for preventing Staphylococcus aureus infections after cardiothoracic surgery: a randomized trial.

IMPORTANCE: Infections due to Staphylococcus aureus are serious complications of cardiothoracic surgery. A novel vaccine candidate (V710) containing the highly conserved S. aureus iron surface determinant B is immunogenic and generally well tolerated in volunteers. OBJECTIVE: To evaluate the efficacy and safety of preoperative vaccination in preventing serious postoperative S. aureus infection in patients undergoing cardiothoracic surgery. DESIGN, SETTING, AND PARTICIPANTS: Double-blind, randomized, event-driven trial conducted between December 2007 and August 2011 among 8031 patients aged 18 years or older who were scheduled for full median sternotomy within 14 to 60 days of vaccination at 165 sites in 26 countries. INTERVENTION: Participants were randomly assigned to receive a single 0.5-mL intramuscular injection of either V710 vaccine, 60 µg (n = 4015), or placebo (n = 4016). MAIN OUTCOME MEASURES: The primary efficacy end point was prevention of S. aureus bacteremia and/or deep sternal wound infection (including mediastinitis) through postoperative day 90. Secondary end points included all S. aureus surgical site and invasive infections through postoperative day 90. Three interim analyses with futility assessments were planned. RESULTS: The independent data monitoring committee recommended termination of the study after the second interim analysis because of safety concerns and low efficacy. At the end of the study, the V710 vaccine was not significantly more efficacious than placebo in preventing either the primary end points (22/3528 V710 vaccine recipients [2.6 per 100 person-years] vs 27/3517 placebo recipients [3.2 per 100 person-years]; relative risk, 0.81; 95% CI, 0.44-1.48; P = .58) or secondary end points despite eliciting robust antibody responses. Compared with placebo, the V710 vaccine was associated with more adverse experiences during the first 14 days after vaccination (1219/3958 vaccine recipients [30.8%; 95% CI, 29.4%-32.3%] and 866/3967 placebo recipients [21.8%; 95% CI, 20.6%-23.1%], including 797 [20.1%; 95% CI, 18.9%-21.4%] and 378 [9.5%; 95% CI, 8.6%-10.5%] with injection site reactions and 66 [1.7%; 95% CI, 1.3%-2.1%] and 51 [1.3%; 95% CI, 1.0%-1.7%] with serious adverse events, respectively) and a significantly higher rate of multiorgan failure during the entire study (31 vs 17 events; 0.9 [95% CI, 0.6-1.2] vs 0.5 [95% CI, 0.3-0.8] events per 100 person-years; P = .04). Although the overall incidence of vaccine-related serious adverse events (1 in each group) and the all-cause mortality rate (201/3958 vs 177/3967; 5.7 [95% CI, 4.9-6.5] vs 5.0 [95% CI, 4.3-5.7] deaths per 100 person-years; P = .20) were not statistically different between groups, the mortality rate in patients with staphylococcal infections was significantly higher among V710 vaccine than placebo recipients (15/73 vs 4/96; 23.0 [95% CI, 12.9-37.9] vs 4.2 [95% CI, 1.2-10.8] per 100 person-years; difference, 18.8 [95% CI, 8.0-34.1] per 100 person-years). CONCLUSIONS AND RELEVANCE: Among patients undergoing cardiothoracic surgery with median sternotomy, the use of a vaccine against S. aureus compared with placebo did not reduce the rate of serious postoperative S. aureus infections and was associated with increased mortality among patients who developed S. aureus infections. These findings do not support the use of the V710 vaccine for patients undergoing surgical interventions. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00518687.

The immunogenicity and safety of different formulations of a novel Staphylococcus aureus vaccine (V710): results of two Phase I studies.

Merck V710 is a novel vaccine that contains the highly conserved Staphylococcus aureus iron surface determinant B (IsdB) protein. V710 has induced positive immune responses in healthy subjects. The purpose of the two studies described herein was to evaluate the immunogenicity and safety of two different formulations of V710. Both studies were randomized, controlled, double-blind, parallel-group trials. Study 1 compared liquid, aluminum-adjuvanted V710 (30 µg) with liquid, non-adjuvanted V710 (30 µg) in a 1:1 ratio in 64 healthy adults (18-70 years). Study 2 compared non-adjuvanted lyophilized V710 (60 µg) with saline placebo in a 4:1 ratio in 51 healthy adults (18-80 years). Blood was collected at screening and up to Day 360 postvaccination in Study 1, and at screening and up to Day 84 postvaccination in Study 2. Sera were analyzed for IsdB-specific antibodies using a total IgG assay. The primary endpoints in Study 1 were the proportion of patients with a positive immune response (≥2-fold rise in IsdB-specific IgG antibody level) the geometric mean concentration (GMC), and the geometric mean-fold rise (GMFR), all from baseline at Day 14. The primary endpoint in Study 2 was the GMFR in IsdB-specific IgG antibody concentration from baseline at Day 14. In Study 1, 84.4% responded in the adjuvanted V710 group, and 71.9% in the non-adjuvanted V710 group. The GMC was 115.4 µg/mL in the adjuvanted group and 99.1 µg/mL in the nonadjuvanted group. The GMFR in antibody concentration in the group receiving aluminum-adjuvanted V710 was 4.5 and the GMFR in the group receiving non-adjuvanted V710 was 4.0. In Study 2, the GMFR in antibody concentration in the V710 group was 5.3, and 80.5% had a positive immune response. None responded in the placebo group. Positive immune response was seen in the active treatment groups over the full duration of each study. There were no serious adverse experiences (AE) in either study, and no patients discontinued due to an AE. There were no clinically meaningful differences in AEs between groups in either study. In conclusion, V710, both with and without aluminum adjuvant, and in both liquid and lyophilized formulations, was immunogenic within 14 days of vaccination. All treatments showed similar safety profiles.

Pentavalent rotavirus vaccine in developing countries: safety and health care resource utilization.

OBJECTIVE: In the international, placebo-controlled, Rotavirus Efficacy and Safety Trial, the pentavalent rotavirus vaccine reduced the rate of rotavirus-attributable hospitalizations and emergency department visits by 95%. This study investigated the effect in Jamaica. METHODS: The vaccine effect on rates of hospitalizations and emergency department visits in Jamaica was evaluated in both modified intention-to-treat and per-protocol analyses. Rates of serious adverse events, including intussusception, also were compared between groups. RESULTS: A total of 1804 Jamaican infants, 6 to 12 weeks of age at entry and primarily from low/middle-income families of African heritage, received ≥1 dose. During the first year after dose 1, there were 2 and 11 hospitalizations or emergency department visits attributable to rotavirus gastroenteritis involving any serotype among 831 evaluable vaccine recipients and 809 evaluable placebo recipients, respectively (rate reduction: 82.2% [95% confidence interval: 15.1%-98.0%]). In the per-protocol analysis, all 8 G1 to G4 rotavirus-attributable events that occurred ≥2 weeks after dose 3 were in the placebo group (rate reduction: 100% [95% confidence interval: 40.9%-100%]). Of the 1802 subjects included in the safety analyses, intussusception was confirmed for 1 vaccine recipient (115 days after the third dose) and 3 placebo recipients. One vaccine recipient and 3 placebo recipients died during the follow-up period, but none of the deaths was considered to be vaccine-related. CONCLUSIONS: In this posthoc subgroup analysis, the vaccine reduced health care resource utilization attributable to rotavirus gastroenteritis, without increased risk of intussusception or other serious adverse events, among infants in a resource-limited country.

Safety and immunogenicity of a novel Staphylococcus aureus vaccine: results from the first study of the vaccine dose range in humans.

Merck V710 is a novel vaccine containing the conserved Staphylococcus aureus iron surface determinant B shown to be protective in animal models. A phase I, multicenter, double-blind study of the dose range was conducted to assess the immunogenicity and safety of an adjuvanted liquid formulation of V710. A total of 124 adults (18 to 55 years of age) were randomized 1:1:1:1 to receive one 0.5-ml intramuscular injection of V710 (5 µg, 30 µg, or 90 µg) or saline placebo. A positive immune response was defined as at least a 2-fold increase in IsdB-specific IgG levels from baseline levels. Local and systemic adverse events were assessed for 5 and 14 days, respectively, following vaccination. Positive immune responses were detected in 12 (67%) of the 18 subjects in the groups receiving 30 and 90 µg V710 tested at day 10. At day 14, a significantly greater proportion of subjects manifested a positive immune response with higher geometric mean concentrations in the V710 30-µg (86%; geometric mean concentration of 116 µg/ml) and 90-µg (87%; geometric mean concentration of 131 µg/ml) dose groups than in the V710 5-µg (29%; geometric mean concentration of 51 µg/ml) or placebo (4%; geometric mean concentration of 23 µg/ml) groups. Immune responses were durable through day 84. Subjects <40 and ≥40 years of age had comparable immune responses. The most common adverse events were injection-site pain, nausea, fatigue, and headache, usually of mild intensity. No immediate reactions or serious adverse events were reported. In this first study of V710 in humans, a single 30-µg or 90-µg dose was more immunogenic than the 5-µg dose or placebo. Immune responses were evident by 10 to 14 days after vaccination in most responders.

Safety and efficacy of a pentavalent human-bovine (WC3) reassortant rotavirus vaccine.

BACKGROUND: Rotavirus is a leading cause of childhood gastroenteritis and death worldwide. METHODS: We studied healthy infants approximately 6 to 12 weeks old who were randomly assigned to receive three oral doses of live pentavalent human-bovine (WC3 strain) reassortant rotavirus vaccine containing human serotypes G1, G2, G3, G4, and P[8] or placebo at 4-to-10-week intervals in a blinded fashion. Active surveillance was used to identify subjects with serious adverse and other events. RESULTS: The 34,035 infants in the vaccine group and 34,003 in the placebo group were monitored for serious adverse events. Intussusception occurred in 12 vaccine recipients and 15 placebo recipients within one year after the first dose including six vaccine recipients and five placebo recipients within 42 days after any dose (relative risk, 1.6; 95 percent confidence interval, 0.4 to 6.4). The vaccine reduced hospitalizations and emergency department visits related to G1-G4 rotavirus gastroenteritis occurring 14 or more days after the third dose by 94.5 percent (95 percent confidence interval, 91.2 to 96.6 percent). In a nested substudy, efficacy against any G1-G4 rotavirus gastroenteritis through the first full rotavirus season after vaccination was 74.0 percent (95 percent confidence interval, 66.8 to 79.9 percent); efficacy against severe gastroenteritis was 98.0 percent (95 percent confidence interval, 88.3 to 100 percent). The vaccine reduced clinic visits for G1-G4 rotavirus gastroenteritis by 86.0 percent (95 percent confidence interval, 73.9 to 92.5 percent). CONCLUSIONS: This vaccine was efficacious in preventing rotavirus gastroenteritis, decreasing severe disease and health care contacts. The risk of intussusception was similar in vaccine and placebo recipients. (ClinicalTrials.gov number, NCT00090233.)