An Exploratory Study of the Salivary Immunoglobulin A Responses to 1 Dose of a Norovirus Virus-Like Particle Candidate Vaccine in Healthy Adults.

As noroviruses are transmitted through the fecal-oral route, we investigated humoral and mucosal (salivary immunoglobulin A [IgA]) immune responses in a phase 2 trial of Takeda's bivalent norovirus virus-like particle (VLP) vaccine candidate in 50 healthy 18- to 49-year-olds. The vaccine had an acceptable tolerability profile and induced rapid, robust humoral immune responses after 1 intramuscular dose of vaccine candidate. Seroresponses were evident 8 days after vaccination as panimmunoglobulin, IgA, and histo-blood group antigen-blocking antibodies against both vaccine GI.1 and GII.4c genotypes. Salivary IgA levels were approximately 1000-fold lower than serum concentrations, and moderately or strongly correlated with the serum IgA titers at all time-points.

Persistence of Antibodies to 2 Virus-Like Particle Norovirus Vaccine Candidate Formulations in Healthy Adults: 1-Year Follow-up With Memory Probe Vaccination.

BACKGROUND: We previously reported the tolerability and immunogenicity 1 month after intramuscular administration of 2 bivalent virus-like particle (VLP)-based candidate norovirus vaccine formulations in adults. We now describe the persistence of immunity and responses to a memory probe vaccination 1 year later. METHODS: A total of 454 healthy men and women aged 18-49 years in 3 equal groups received placebo (saline) or 15/50 or 50/50 vaccine formulations (ie, 15 or 50 µg of GI.1 genotype VLPs, respectively, and 50 µg of GII.4c VLPs) with MPL and Al(OH)3. Immunogenicity and safety were assessed up to day 365, when 351 participants received a memory probe vaccination of 15 µg each of GI.1 and GII.4c VLPs with Al(OH)3. RESULTS: No safety signals were detected up to 1 year after the first vaccination. Pan-immunoglobulin, immunoglobulin A, and histo-blood group antigen-blocking (HBGA) antibody levels among vaccinees waned but remained higher than levels before vaccination and levels in placebo recipients on days 180 and 365. Memory probe vaccination increased all antibody titers. Levels of HBGA antibodies to GI.1 but not GII.4c were higher after the first vaccination in candidate vaccine groups, compared with those in the placebo group. CONCLUSION: Levels of antibodies to both candidate norovirus VLP formulations persisted above baseline levels for at least 1 year after primary vaccination. HBGA-blocking responses to the memory probe for GI.1 but not GII.4c displayed characteristics of immune memory. CLINICAL TRIALS REGISTRATION: NCT02142504.

Safety and Immunogenicity of Different Formulations of Norovirus Vaccine Candidate in Healthy Adults: A Randomized, Controlled, Double-Blind Clinical Trial.

Background: We investigated safety and immunogenicity of 1-2 doses of different bivalent virus-like particle (VLP) norovirus vaccine candidate (NoV) formulations in healthy 18- to 64-year-olds. Methods: On days 1 and 28, participants (n = 420) randomized to 14 equal groups received intramuscular control vaccine (hepatitis A) or 1 of 11 NoV formulations containing varying dosages of GI.1 and GII.4c genotype VLP antigens with aluminum hydroxide [Al(OH)3], and 0 µg, 15 µg, or 50 µg monophosphoryl lipid A (MPL). Immunogenicity was assessed on days 1, 28, 56, 208 and 393. Solicited local and systemic reactions were recorded for 7 days, unsolicited adverse events (AEs) until day 56, and serious AEs throughout the trial. Results: All NoV formulations induced similar increases in pan-immunoglobulin, immunoglobulin A, and histo-blood group binding antigen-blocking antibodies by day 56, mostly after 1 dose, that persisted above baseline to day 393. Higher GI.1 content interfered with GII.4c responses, and responses did not benefit from MPL. Overall reactogenicity consisted of mainly mild injection site pain, headache, and fatigue. No vaccine-related serious AEs were reported. Conclusions: All candidate NoV formulations were well tolerated. Overall, 15 µg GI.1/50 µg GII.4c elicited the best balance of immunogenicity with no clear benefit of MPL, and is the candidate formulation being taken forward in clinical development. Clinical Trials Registration: NCT02038907.

Impact of Pre-exposure History and Host Genetics on Antibody Avidity Following Norovirus Vaccination.

Background: Development of high avidity, broadly neutralizing antibodies (Abs) is a priority after vaccination against rapidly evolving, widely disseminated viruses like human norovirus. After vaccination with a multivalent GI.1 and GII.4c norovirus virus-like particle (VLP) vaccine candidate adjuvanted with alum and monophosphoryl lipid A (MPL), blockade Ab titers peaked early, with no increase in titer following a second vaccine dose. Methods: Blockade Ab relative avidity was evaluated by measuring the slope of blockade Ab neutralization curves. Results: Blockade Ab avidity to the GI.1 vaccine component peaked at day 35 (7 days after dose 2). Avidities to heterotypic genogroup I VLPs were not sustained at day 35 after vaccination or GI.1 infection, as measured from archived sera. Only secretor-positive participants maintained high avidity blockade Ab to GI.1 at day 180. Avidity to the GII.4c vaccine component peaked at day 7, remained elevated through day 180, and was not secretor dependent. Avidity to an immunologically novel GII.4 strain VLP correlated with preexisting Ab titer to an ancestral strain Epitope A. Conclusions: Host genetics and pre-exposure history shape norovirus vaccine Ab responses, including blockade Ab avidity. Avidity of potentially neutralizing Ab may be an important metric for evaluating vaccine responses to highly penetrant viruses with cross-reactive serotypes.

Rapid Responses to 2 Virus-Like Particle Norovirus Vaccine Candidate Formulations in Healthy Adults: A Randomized Controlled Trial.

BACKGROUND: Noroviruses pose a significant public health risk, particularly in very young individuals, older adults, and individuals with underlying conditions. We assessed 2 bivalent norovirus virus-like particle (VLP) vaccine candidate formulations in healthy adults aged 18-49 years. METHODS: Enrolled subjects (n = 454) randomly assigned among 3 groups received intramuscular placebo (saline) or vaccines containing either 15 µg or 50 µg of GI.1 VLP and 50 µg GII.4 VLP (15/50 and 50/50 formulations) adjuvanted with monophosphoryl lipid A and Al(OH)3 We present safety and immunogenicity assessments up to 28 days after vaccination. RESULTS: No vaccine-related serious adverse events or adverse events of special interest were reported. Reactions were mainly mild to moderate, the most frequent being transient pain, in 8%, 64%, and 73% of placebo, 15/50, and 50/50 groups, respectively; transient myalgia, headache, and fatigue were the commonest systemic adverse events. Subjects assessed per protocol (n = 442) displayed rapid immune responses to vaccination, peaking by days 7-10 and persisting through day 28. GI.1 responses were highest with the 50/50 formulation, but GII.4 responses were higher with the 15/50 formulation. CONCLUSIONS: Both candidate VLP vaccines were well tolerated and elicited robust immune responses by 7-10 days that persisted through day 28. The 15/50 formulation displayed the best balance of tolerability and immunogenicity. CLINICAL TRIALS REGISTRATION: NCT02142504.

Norovirus vaccine against experimental human GII.4 virus illness: a challenge study in healthy adults.

BACKGROUND: Vaccines against norovirus, the leading cause of acute gastroenteritis, should protect against medically significant illness and reduce transmission. METHODS: In this randomized, double-blind, placebo-controlled trial, 18- to 50-year-olds received 2 injections of placebo or norovirus GI.1/GII.4 bivalent vaccine-like particle (VLP) vaccine with 3-O-desacyl-4'-monophosphoryl lipid A (MPL) and alum. Participants were challenged as inpatients with GII.4 virus (4400 reverse transcription polymerase chain reaction [RT-PCR] units), and monitored for illness and infection. RESULTS: Per protocol, 27 of 50 (54.0%) vaccinees and 30 of 48 (62.5%) controls were infected. Using predefined illness and infection definitions, vaccination did not meet the primary endpoint, but self-reported cases of severe (0% vaccinees vs. 8.3% controls; P = .054), moderate or greater (6.0% vs. 18.8%; P = .068), and mild or greater severity of vomiting and/or diarrhea (20.0% vs. 37.5%; P = .074) were less frequent. Vaccination also reduced the modified Vesikari score from 7.3 to 4.5 (P = .002). Difficulties encountered were low norovirus disease rate, and inability to define illness by quantitative RT-PCR or further antibody rise in vaccinees due to high vaccine-induced titers. By day 10, 11 of 49 (22.4%) vaccinees were shedding virus compared with 17 of 47 (36.2%) placebo recipients (P = .179). CONCLUSIONS: Bivalent norovirus VLP vaccine reduced norovirus-related vomiting and/or diarrhea; field efficacy studies are planned. Clinical Trials Registration. NCT01609257.

Broad blockade antibody responses in human volunteers after immunization with a multivalent norovirus VLP candidate vaccine: immunological analyses from a phase I clinical trial.

BACKGROUND: Human noroviruses (NoVs) are the primary cause of acute gastroenteritis and are characterized by antigenic variation between genogroups and genotypes and antigenic drift of strains within the predominant GII.4 genotype. In the context of this diversity, an effective NoV vaccine must elicit broadly protective immunity. We used an antibody (Ab) binding blockade assay to measure the potential cross-strain protection provided by a multivalent NoV virus-like particle (VLP) candidate vaccine in human volunteers. METHODS AND FINDINGS: Sera from ten human volunteers immunized with a multivalent NoV VLP vaccine (genotypes GI.1/GII.4) were analyzed for IgG and Ab blockade of VLP interaction with carbohydrate ligand, a potential correlate of protective immunity to NoV infection and illness. Immunization resulted in rapid rises in IgG and blockade Ab titers against both vaccine components and additional VLPs representing diverse strains and genotypes not represented in the vaccine. Importantly, vaccination induced blockade Ab to two novel GII.4 strains not in circulation at the time of vaccination or sample collection. GII.4 cross-reactive blockade Ab titers were more potent than responses against non-GII.4 VLPs, suggesting that previous exposure history to this dominant circulating genotype may impact the vaccine Ab response. Further, antigenic cartography indicated that vaccination preferentially activated preexisting Ab responses to epitopes associated with GII.4.1997. Study interpretations may be limited by the relevance of the surrogate neutralization assay and the number of immunized participants evaluated. CONCLUSIONS: Vaccination with a multivalent NoV VLP vaccine induces a broadly blocking Ab response to multiple epitopes within vaccine and non-vaccine NoV strains and to novel antigenic variants not yet circulating at the time of vaccination. These data reveal new information about complex NoV immune responses to both natural exposure and to vaccination, and support the potential feasibility of an efficacious multivalent NoV VLP vaccine for future use in human populations. TRIAL REGISTRATION: ClinicalTrials.gov NCT01168401.

Needle-free jet injection for administration of influenza vaccine: a randomised non-inferiority trial.

BACKGROUND: Administration of vaccines by needle-free technology such as jet injection might offer an alternative to needles and syringes that avoids the issue of needle phobia and the risk of needle-stick injury. We aimed to assess the immunogenicity and safety of trivalent influenza vaccine given by needle-free jet injector compared with needle and syringe. METHODS: For this randomised, comparator-controlled trial, we randomly assigned (1:1) healthy adults (aged 18-64 years) who attended one of four employee health clinics in the University of Colorado health system, with stratification by site, to receive one dose of the trivalent inactivated influenza vaccine Afluria given either intramuscularly with a needle-free jet injector (Stratis; PharmaJet, Golden, CO, USA) or with needle and syringe. Randomisation was done with a computer-generated randomisation schedule with a block size of 100. Because of the nature of the study, masking of participants was not possible. Immunogenicity was assessed by measurement of the hemagglutination inhibition antibody titres in serum for the three viral strains included in the vaccine. We included six coprimary endpoints: three strain-specific geometric mean titre ratios and the absolute differences in three strain-specific seroconversion rates. The immune response of the jet injector group was regarded as non-inferior to that of the needle and syringe group if both the upper bound of each of the three 95% CIs for the strain-specific geometric mean titre ratios was 1.5 or less, and the upper bound of the three 95% CIs for the strain-specific seroconversion rate differences was less than 10 percentage points. We used t test for group comparison. This study is registered with ClinicalTrials.gov, number NCT01688921. FINDINGS: During the 2012-13 influenza season of the northern hemisphere, we allocated 1250 participants to receive vaccination by needle-free jet injector (n=627) or needle and syringe (n=623). In the intention-to-treat immunogenicity population, all participants with two serum samples were included (575 in the jet injector group and 574 in the needle and syringe group). The immune response to Afluria when given by needle-free jet injector met the criteria for non-inferiority for all six coprimary endpoints. The jet injector group met the geometric mean titre criterion for non-inferiority for the A/H1N1, A/H3N2, and B strains (upper bound of the 95% CI for the geometric mean titre ratios were 1·10 for A/H1N1, 1·17 for A/H3N2, and 1·04 for B strains). The jet injector group met the seroconversion rate criterion for non-inferiority for the A/H1N1, A/H3N2, and B strains (upper bound of the 95% CI of the seroconversion rate differences were 6·0% for A/H1N1, 7·0% for A/H3N2, and 5·7% for B strains). We recorded serious adverse events in three participants, none of which were study related. INTERPRETATION: The immune response to influenza vaccine given with the jet injector device was non-inferior to the immune response to influenza vaccine given with needle and syringe. The device had a clinically acceptable safety profile, but was associated with a higher frequency of local injection site reactions than was the use of needle and syringe. The Stratis needle-free jet injector device could be used as an alternative method of administration of Afluria trivalent influenza vaccine. FUNDING: Biomedical Advanced Research and Development Authority (BARDA), PATH, bioCSL, and PharmaJet.

A novel intramuscular bivalent norovirus virus-like particle vaccine candidate--reactogenicity, safety, and immunogenicity in a phase 1 trial in healthy adults.

BACKGROUND: Noroviruses are the most important viral causes of gastroenteritis-related morbidity and mortality. A randomized, double-blind, placebo-controlled study evaluated an adjuvanted bivalent intramuscular norovirus virus-like particle (VLP) vaccine. METHODS: Forty-eight adults aged 18-49 years received either 2 doses containing genotype GI.1 VLP and a consensus GII.4 VLP or 2 doses of placebo. Doses (5 µg, 15 µg, 50 µg, or 150 µg of each VLP) were administered 4 weeks apart in the first stage. Subsequently, 54 adults, aged 18-49 (n=16), 50-64 (n=19), and 65-85 (n=19) years, received 2 doses of vaccine containing 50 µg of each VLP. Total and class-specific antibody responses, as well as histoblood group antigen (HBGA) blocking antibody responses, were measured before and after each dose. RESULTS: Local reactions were mainly injection site pain/tenderness, with no reported fever or vaccine-related serious adverse events. One dose of vaccine containing 50 µg of each VLP increased GI.1 geometric mean titers (GMTs) by 118-fold, 83-fold, and 24-fold and increased GII.4 GMTs by 49-fold, 25-fold, and 9-fold in subjects aged 18-49, 50-64, and 65-83 years, respectively. Serum antibody responses peaked at day 7 after the first dose, with no evidence of boosting following a second dose. Most subjects achieved HBGA-blocking antibody titers of ≥200. CONCLUSIONS: The vaccine was well tolerated and immunogenic. Rapid immune response to a single dose may be particularly useful in military personnel and travelers and in the control of outbreaks. Clinical Trials Registration. NCT01168401.

Norovirus vaccine against experimental human Norwalk Virus illness.

BACKGROUND: Noroviruses cause epidemic and sporadic acute gastroenteritis. No vaccine is available to prevent norovirus illness or infection. METHODS: We conducted a randomized, double-blind, placebo-controlled, multicenter trial to assess the safety, immunogenicity, and efficacy of an investigational, intranasally delivered norovirus viruslike particle (VLP) vaccine (with chitosan and monophosphoryl lipid A as adjuvants) to prevent acute viral gastroenteritis after challenge with a homologous viral strain, Norwalk virus (genotype GI.1). Healthy adults 18 to 50 years of age received two doses of either vaccine or placebo and were subsequently inoculated with Norwalk virus and monitored for infection and gastroenteritis symptoms. RESULTS: Ninety-eight persons were enrolled and randomly assigned to receive vaccine (50 participants) or placebo (48 participants), and 90 received both doses (47 participants in the vaccine group and 43 in the placebo group). The most commonly reported symptoms after vaccination were nasal stuffiness, nasal discharge, and sneezing. Adverse events occurred with similar frequency among vaccine and placebo recipients. A Norwalk virus-specific IgA seroresponse (defined as an increase by a factor of 4 in serum antibody levels) was detected in 70% of vaccine recipients. Seventy-seven of 84 participants inoculated with Norwalk virus were included in the per-protocol analysis. Vaccination significantly reduced the frequencies of Norwalk virus gastroenteritis (occurring in 69% of placebo recipients vs. 37% of vaccine recipients, P=0.006) and Norwalk virus infection (82% of placebo recipients vs. 61% of vaccine recipients, P=0.05). CONCLUSIONS: This norovirus VLP vaccine provides protection against illness and infection after challenge with a homologous virus. (Funded by LigoCyte Pharmaceuticals and the National Institutes of Health; ClinicalTrials.gov number, NCT00973284.).

Immunogenicity and tolerability of a bivalent virus-like particle norovirus vaccine candidate in children from 6 months up to 4 years of age: A phase 2 randomized, double-blind trial.

We conducted a dose-finding phase 2 study of the HilleVax bivalent virus-like particle (VLP) vaccine candidate (HIL-214) in two cohorts of children, 6-≤12 months and 1-≤4 years of age (N = 120 per cohort), in Panama and Colombia (ClinicalTrials.gov, identifier NCT02153112). On Day 1, children randomized to one of the four equal groups received intramuscular injections of four different HIL-214 formulations containing 15/15, 15/50, 50/50, or 50/150 µg of GI.1/GII.4c genotype VLPs and 0.5 mg Al(OH)3. On Day 29, half the children in each group received a second vaccination (N = 60), while the other half received saline placebo injections to maintain the blind. VLP-specific ELISA Pan-Ig and histo-blood group binding antigen-blocking antibodies (HBGA) were measured on Days 1, 29, 57 and 210. On Day 29, after one dose, there were large Pan-Ig and HBGA responses in both age cohorts with some indication of dose-dependence, and higher geometric mean titers (GMT) in the older children. A further increase in titers was observed 28 days after a second dose in the 6-≤12-month-old groups, but less so in the 1-≤4-year-old groups; GMTs at Day 57 were broadly similar across doses and in both age groups. GMTs of Pan-Ig and HBGA persisted above baseline up to Day 210. All formulations were well tolerated with mostly mild-to-moderate transient solicited adverse events reported by parents/guardians, and no vaccine-related serious adverse events occurred. Further development of HIL-214 is warranted to protect the most susceptible young children against norovirus.

Immunogenicity of a bivalent virus-like particle norovirus vaccine in children from 1 to 8 years of age: A phase 2 randomized, double-blind study.

BACKGROUND: Young children can suffer severe consequences of norovirus gastroenteritis. We performed a dose-finding study of a bivalent virus-like particle (VLP) vaccine candidate (TAK-214) in healthy 1-8-year-old children. METHODS: In this phase 2 study two age cohorts (1-3 and 4-8 years of age inclusive, N = 120 per cohort) of children enrolled from Finland, Panama and Colombia were initially randomized 1:1:1:1 to four groups which were further split into two equal subgroups, to receive one or two intramuscular doses of four TAK-214 formulations containing 15/15, 15/50, 50/50 or 50/150 µg of GI.1/GII.4c genotype VLPs and 0.5 mg Al(OH)3 at 28 days interval. ELISA Pan-Ig and histoblood group antigen-blocking (HBGA) antibodies against each VLP were measured on days 1, 29, 57 and 210. Parents/guardians recorded solicited local and systemic adverse events (AE) and any unsolicited or serious AEs (SAE). RESULTS: All formulations were well-tolerated across both age cohorts and dosage groups with no vaccine-related SAEs reported. Solicited AEs were mostly mild-to-moderate, resolved quickly, and did not increase after the second dose. Pan-Ig and HBGA responses induced after one dose were only slightly increased by the second dose. Across dose groups at Day 29 after one dose GI.1 Pan Ig seroresponse rates (SRR) were 82-97% and 81-96% and GII.4c SRR were 79-97% and 80-91% in 1-3 and 4-8 year-olds, respectively. Respective rates were to 92-93% and 73-92% for GI.1, and 77-100% and 62-83% for GII.4c at Day 57 following two doses. HBGA responses had similar profiles. Both Pan Ig and HBGA geometric mean titers persisted above baseline up to Day 210. CONCLUSIONS: All dosages of TAK-214 displayed acceptable reactogenicity in 1-8-year-old children and induced robust, durable immune responses after one dose which are further increased after two doses.

Adjuvanted intranasal Norwalk virus-like particle vaccine elicits antibodies and antibody-secreting cells that express homing receptors for mucosal and peripheral lymphoid tissues.

BACKGROUND: Noroviruses cause significant morbidity and mortality from acute gastroenteritis in all age groups worldwide. METHODS: We conducted 2 phase 1 double-blind, controlled studies of a virus-like particle (VLP) vaccine derived from norovirus GI.1 genotype adjuvanted with monophosphoryl lipid A (MPL) and the mucoadherent chitosan. Healthy subjects 18-49 years of age were randomized to 2 doses of intranasal Norwalk VLP vaccine or controls 21 days apart. Study 1 evaluated 5-, 15-, and 50-µg dosages of Norwalk antigen, and study 2 evaluated 50- and 100-µg dosages. Volunteers recorded symptoms for 7 days after dosing, and safety was followed up for 180 days. Blood samples were collected for serological profile, antibody secreting cells (ASCs), and analysis of ASC homing receptors. RESULTS: The most common symptoms were nasal stuffiness, discharge, and sneezing. No vaccine-related serious adverse events occurred. Norwalk VLP-specific immunoglobulin G and immunoglobulin A antibodies increased 4.8- and 9.1-fold, respectively, for the 100-µg dosage level. All subjects tested who received the 50- or 100-µg vaccine dose developed immunoglobulin A ASCs. These cells expressed molecules associated with homing to mucosal and peripheral lymphoid tissues. CONCLUSIONS: The intranasal monovalent adjuvanted Norwalk VLP vaccine was well tolerated and highly immunogenic and is a candidate for additional study.

Efficacy of an intramuscular bivalent norovirus GI.1/GII.4 virus-like particle vaccine candidate in healthy US adults.

BACKGROUND: We performed this first-in-human efficacy trial of Takeda's bivalent norovirus vaccine candidate (TAK-214) against moderate or severe acute gastroenteritis (AGE) in healthy adults. METHODS: This double-blind, randomized, placebo-controlled phase 2b trial was conducted over two winter seasons in 18-49 year-old US Navy recruits. Participants were randomized (1:1) to receive intramuscular injections of saline placebo (N = 2,357) or TAK-214 [15 µg GI.1 and 50 µg GII.4c VLPs, 0.5 mg Al(OH)3] (N = 2,355), and monitored for 45 days post-vaccination for AGE. Norovirus genotypes were identified by RT-PCR and sequencing of stool/vomitus samples. Sera from AGE cases were used to assess immune responses as genotype-specific histo-blood group antigen (HBGA)-blocking antibodies. FINDINGS: With low rates of homotypic norovirus AGE detected the statistical analysis was proactively modified to account for AGE due to any norovirus genotype. Of the 48 norovirus AGE cases of "any severity", 29 in placebo and 19 in vaccinees, causative genotypes were GI.1 (n = 1), G1.7a (n = 1), GII.2 (n = 39) and GII.4 (n = 7). Applying predefined definitions of moderate or severe AGE gave 26 vs. 10 cases due to any norovirus genotype in placebo vs. vaccine groups, a vaccine efficacy (VE) of 61.8% (95.01% CI, 20.8 to 81.6; p = 0.0097). Five vs. one moderate or severe cases due to vaccine GI.1/GII.4 homotypic genotypes in placebo vs. vaccine arms gave a primary endpoint vaccine efficacy of 80.0% (99.99% CI, -1318.1 to 99.7; p = 0.142). Levels of GI.1 and GII.4 HBGA-blocking antibodies were increased in vaccinees and in some placebo AGE cases infected with GII.2, indicating cross-reactivity in the immune responses to different genotypes. INTERPRETATION: Despite limited cases of homotypic norovirus AGE meaning the primary endpoint was not fully evaluable, we showed TAK-214 provided statistically significant efficacy against "any moderate/severe norovirus AGE" principally caused by the heterotypic GII.2 genotype, demonstrating induction of cross-genotype protection.

B-Cell Responses to Intramuscular Administration of a Bivalent Virus-Like Particle Human Norovirus Vaccine.

Human noroviruses (HuNoVs) are a leading cause of acute gastroenteritis worldwide. A virus-like particle (VLP) candidate vaccine induces the production of serum histo-blood group antigen (HBGA)-blocking antibodies, the first identified correlate of protection from HuNoV gastroenteritis. Recently, virus-specific IgG memory B cells were identified to be another potential correlate of protection against HuNoV gastroenteritis. We assessed B-cell responses following intramuscular administration of a bivalent (genogroup I, genotype 1 [GI.1]/genogroup II, genotype 4 [GII.4]) VLP vaccine using protocols identical to those used to evaluate cellular immunity following experimental GI.1 HuNoV infection. The kinetics and magnitude of cellular immunity to G1.1 infection were compared to those after VLP vaccination. Intramuscular immunization with the bivalent VLP vaccine induced the production of antibody-secreting cells (ASCs) and memory B cells. ASC responses peaked at day 7 after the first dose of vaccine and returned to nearly baseline levels by day 28. Minimal increases in ASCs were seen after a second vaccine dose at day 28. Antigen-specific IgG memory B cells persisted at day 180 postvaccination for both GI.1 and GII.4 VLPs. The overall trends in B-cell responses to vaccination were similar to the trends in the responses to infection, where there was a greater bias of an ASC response toward IgA and a memory B-cell response to IgG. The magnitude of the ASC and memory B-cell responses to the GI.1 VLP component of the vaccine was also comparable to that of the responses following GI.1 infection. The production of IgG memory B cells and persistence at day 180 is a key finding and underscores the need for future studies to determine if IgG memory B cells are a correlate of protection following vaccination. (This study has been registered at ClinicalTrials.gov under registration no. NCT01168401.).

A randomized, double-blind study of the safety, transmissibility and phenotypic and genotypic stability of cold-adapted influenza virus vaccine.

BACKGROUND: Live attenuated influenza vaccine (LAIV; FluMist) is a trivalent vaccine containing cold-adapted influenza vaccine viruses that infect and replicate in cells lining the nasopharynx to induce immunity. Recovery of viruses (shedding) is measured by culture of nasal specimens. Shedding of vaccine viruses is not equated with transmission because transmission requires more virus than is detected in many nasal swabs. Previous studies with LAIV did not detect transmission to close contacts. The primary objective of this study was to estimate the probability of transmission to placebo contacts in a day care setting. METHODS: One hundred ninety-seven healthy children aged 9 to 36 months attending day care were randomized to receive vaccine or placebo. Postvaccination viral shedding, safety, genotype and phenotype of shed viruses and probability of transmission were assessed. RESULTS: Eighty percent of 98 vaccine recipients shed at least one vaccine strain. No clinically significant differences in solicited adverse events attributable to vaccine occurred; safety profiles were similar in both groups. Vaccine virus isolates retained their phenotypic characteristics (cold adaptation and temperature sensitivity) and did not revert at nucleotides known to confer an attenuating phenotype. There was one confirmed transmission of a vaccine strain to a single placebo recipient. According to the Reed-Frost model, the calculated probability of transmission to a child after contact with a single vaccinated child was 0.58% (95% confidence interval, 0-1.7%). There was no increased reactogenicity or other safety concerns in the recipient child. CONCLUSIONS: Young children in a day care setting had a high rate of shedding and a low rate of transmission. No clinically significant illness occurred among children who received vaccine or placebo or in the child to whom the vaccine virus was transmitted.

Robust mucosal-homing antibody-secreting B cell responses induced by intramuscular administration of adjuvanted bivalent human norovirus-like particle vaccine.

BACKGROUND: Two major antigenically heterogenous norovirus genogroups (GI and GII) commonly infect humans and are the leading cause of foodborne, viral gastrointestinal infections in adults. METHODS: We assessed B cell responses in participants in a double-blind, placebo-controlled, dose-escalation phase 1 study of the safety and immunogenicity of an intramuscular bivalent norovirus virus-like particle (VLP) vaccine. The vaccine contained a GI.1 VLP (Norwalk) and a consensus GII.4 VLP, representing the two major genotypes that cause human disease, and was administered on days 0 and 28 to healthy adults aged 18-49 years. Four separate cohorts received increasing doses of 5 µg, 15 µg, 50 µg, and 150 µg of each VLP adjuvanted in monophosphoryl lipid A and alum. PBMCs were analyzed for B cell activation and mucosal homing markers (flow cytometry) and VLP-specific and total IgG and IgA Ab-secreting cells (ASCs); and serum titers of VLP-specific IgG, IgA, and Pan-Ig were determined. RESULTS: The vaccine elicited CD27+ CD38+ plasmablasts and high frequencies of ASCs specific for both VLP antigens in the peripheral blood at 7 days after the first dose. The plasmablasts exhibited a mucosal-homing phenotype and included a high proportion of IgA ASCs. Serum antibodies increased as early as 7 days after the first immunization. CONCLUSIONS: The data suggest that a single dose of the IM bivalent norovirus vaccine is effective in activating pre-existing B cell memory. The rapid B cell response and the mucosal homing phenotype of induced ASCs are consistent with anamnestic responses in subjects primed by prior oral norovirus infection. This study is registered at ClinicalTrials.gov Identifier NCT01609257.

Serological Correlates of Protection against a GII.4 Norovirus.

Noroviruses are the leading cause of acute gastroenteritis worldwide, and norovirus vaccine prevention strategies are under evaluation. The immunogenicity of two doses of bivalent genogroup 1 genotype 1 (GI.1)/GII.4 (50 µg of virus-like particles [VLPs] of each strain adjuvanted with aluminum hydroxide and 3-O-desacyl-4'monophosphoryl lipid A [MPL]) norovirus vaccine administered to healthy adults in a phase 1/2 double-blind placebo-controlled trial was determined using virus-specific serum total antibody enzyme-linked immunosorbent assay (ELISA), IgG, IgA, and histoblood group antigen (HBGA)-blocking assays. Trial participants subsequently received an oral live virus challenge with a GII.4 strain, and the vaccine efficacy results were reported previously (D. I. Bernstein et al., J Infect Dis 211:870-878, 2014, doi:10.1093/infdis/jiu497). This report assesses the impact of prechallenge serum antibody levels on infection and illness outcomes. Serum antibody responses were observed in vaccine recipients by all antibody assays, with first-dose seroresponse frequencies ranging from 88 to 100% for the GI.1 antigen and from 69 to 84% for the GII.4 antigen. There was little increase in antibody levels after the second vaccine dose. Among the subjects receiving the placebo, higher prechallenge serum anti-GII.4 HBGA-blocking and IgA antibody levels, but not IgG or total antibody levels, were associated with a lower frequency of virus infection and associated illness. Notably, some placebo subjects without measurable serum antibody levels prechallenge did not become infected after norovirus challenge. In vaccinees, anti-GII.4 HBGA-blocking antibody levels of >1:500 were associated with a lower frequency of moderate-to-severe vomiting or diarrheal illness. In this study, prechallenge serum HBGA antibody titers correlated with protection in subjects receiving the placebo; however, other factors may impact the likelihood of infection and illness after virus exposure. (This study is registered at ClinicalTrials.gov under registration number NCT1609257.).

Safety, efficacy, and effectiveness of live, attenuated, cold-adapted influenza vaccine in an indicated population aged 5-49 years.

BACKGROUND: Three important studies have supported licensure of live, attenuated, cold-adapted influenza vaccine (CAIV-T [FluMist; MedImmune Vaccines]): (1) a pediatric efficacy trial involving children 15-71 months of age, (2) a large safety study of medically attended events occurring among children 1-17 years of age, and (3) an effectiveness trial involving healthy working adults 18-64 years of age. METHODS: During the United States Food and Drug Administration (FDA) review for the approval of CAIV-T for use in healthy persons, additional subgroup analyses were conducted to evaluate the safety, efficacy, and effectiveness of the vaccine, by use of various age subsets not prespecified by the original protocols. CAIV-T is currently approved by the FDA for use in healthy persons 5-49 years of age. In this article, we present data from some of the aforementioned subanalyses. RESULTS: The efficacy of CAIV-T in children >or=5 years of age (age range of the children in year 1 of the study, 60-71 months; age range of the children in year 2 of the study, 60-83 months) was similar to that reported for the entire cohort in year 1 (90.6%; 95% confidence interval [CI], 70.3%-97.1%). In year 2 of the study, efficacy was 86.9% (95% CI, 70.8%-94.1%), despite the presence of antigenically drifted influenza type A/Sydney/5/97 (H3N2), which caused most illnesses that occurred in year 2. Safety outcomes for children 5-17 years of age revealed no significant difference between vaccine recipients and placebo recipients, with regard to acute respiratory events, acute gastrointestinal events, systemic bacterial infection, or rare events possibly related to influenza. Effectiveness among adults 18-49 years of age was similar to that reported for the entire cohort--for example, for occurrence of severe febrile illness, there was a 19.5% reduction (P=.02) in adults. CONCLUSIONS: The present reanalysis summarizes data on the indicated uses for CAIV-T in the indicated population aged 5-49 years.

Effect of yearly vaccinations with live, attenuated, cold-adapted, trivalent, intranasal influenza vaccines on antibody responses in children.

BACKGROUND: The cold-adapted, trivalent influenza vaccine (CAIV-T) may become an option for annual vaccination. However, there is little information regarding the immune response to repeated immunization with CAIV-T. OBJECTIVE: To determine the antibody response to repeated immunization with CAIV-T and to compare this with the response after the first CAIV-T immunization. DESIGN AND METHODS: Healthy children were offered CAIV-T immunization for 4 consecutive years, and blood samples were taken from a subset in Years 1, 2 and 4. In Year 4, 156 similarly aged children who had not received influenza vaccine previously were immunized with the same CAIV-T. RESULTS: The H3N2 and B components of the CAIV-T induced high antibody titers in Year 1 that were maintained during 4 years. The H1N1 titers were lower than the H3N2 or B titers. Comparison of the group immunized for 4 consecutive years with the group immunized for the first time revealed the following: (1) before immunization yearly immunized subjects were more likely to be seropositive to each of the three vaccine strains than those immunized for the first time (P < 0.05 for each); (2) after immunization the percentage of seropositive subjects to each of the strains was similar; (3) after immunization titers were higher in the subjects immunized for the first time than those immunized yearly (P < 0.05 for H3N2 and B). CONCLUSION: Yearly vaccination with CAIV-T induced high antibody titers, especially to the H3N2 and B strains in the vaccines. The titers in those immunized with CAIV-T for the first time were higher than in those immunized for 4 consecutive years.