Pneumococcal Conjugate Vaccines and Otitis Media: An Appraisal of the Clinical Trials

Streptococcus pneumoniae is the predominant otitis media pathogen and its prevention through effective vaccination could diminish childhood illness and antibiotic use. This paper reviews 5 pneumococcal conjugate vaccine (PCV) trials that used otitis media as an endpoint: Northern California Kaiser Permanente (NCKP; vaccine, 7-valent PCV [PCV7]-CRM); Finnish Otitis Media (FinOM; vaccines, PCV7-CRM or PCV7-OMPC); Native American Trial (vaccine, PCV7-CRM); Pneumococcal Otitis Efficacy Trial (POET; vaccine, 11-valent PCV [PCV11]-PD). For the microbiological endpoint, vaccine efficacy against vaccine-serotype pneumococcal otitis media was about 60% across trials. Against the clinical endpoint of all episodes, vaccine efficacy was 7% (PCV7-CRM/NCKP), 6% (PCV7-CRM/FinOM), −1% (PCV7-OMPC/FinOM), and −0.4% (PCV7-CRM/Native American Trial); 34% against first episodes of ear, nose, and throat specialist-referral cases (PCV11-PD/POET). Both follow-up through 2 years of age, for the 5 trials, and long-term follow-up, for PCV7-CRM/NCKP and PCV7-CRM/FinOM, demonstrated greater vaccine efficacy against recurrent AOM and tympanostomy-tube placement, suggesting that vaccination against early episodes of AOM may prevent subsequent episodes of complicated otitis media. Although study designs varied by primary endpoint measured, age at follow-up, source of middle-ear fluid for culture, case ascertainment, and type of randomization, each clinical trial demonstrated vaccine efficacy against microbiological and/or clinical otitis media

Nasopharyngeal Carriage of Streptococcus pneumoniae Shortly before Vaccination with a Pneumococcal Conjugate Vaccine Causes Serotype-Specific Hyporesponsiveness in Early Infancy

Background. The antibody response to pneumococcal conjugate vaccines (PCVs) in infants is variable. Factors responsible for this variability have not been fully elucidated. The objective of this study was to investigate whether pneumococcal carriage around the time of the first dose of 7-valent PCV (PCV7) affects serotype-specific immunologic response. Methods. Healthy 2-month old infants were randomized to receive 2 (at the ages of 4 and 6 months) or 3 (at the ages of 2, 4, and 6 months) PCV7 doses and a booster dose (at the age of 12 months). Nasopharyngeal or oropharyngeal specimens were obtained for culture shortly before the first PCV7 dose. Serotype-specific immunoglobulin (Ig) G levels were measured at ages 2, 7, and 13 months. Results. Of 545 children studied, 332 received a booster dose. The most common serotypes carried around the time of the first PCV7 dose were 6B (n = 37), 19F (n = 22), and 23F (n = 14). In carriers before the first dose, the IgG response to the carried serotype after 2 or 3 doses was significantly lower than in noncarriers. In contrast, response to the noncarried serotypes was not affected. Although all children responded to the booster dose, the response to the originally carried serotype was generally lower. Conclusions. Serotype-specific hyporesponsiveness to PCV7 after pneumococcal carriage in infants is demonstrated for the first time. This phenomenon was common, lasted for at least several months, and was only partially overcome by the 12-month booster. Trial registration. isrctn.org identifier: ISRCTN2844584

Live-attenuated Mycobacterium tuberculosis vaccine MTBVAC versus BCG in adults and neonates: a randomised controlled, double-blind dose-escalation trial

Background: Infants are a key target population for new tuberculosis vaccines. We assessed the safety and immunogenicity of the live-attenuated Mycobacterium tuberculosis vaccine candidate MTBVAC in adults and infants in a region where transmission of tuberculosis is very high. Methods: We did a randomised, double-blind, BCG-controlled, dose-escalation trial at the South African Tuberculosis Vaccine Initiative site near Cape Town, South Africa. Healthy adult community volunteers who were aged 18–50 years, had received BCG vaccination as infants, were HIV negative, had negative interferon-¿ release assay (IGRA) results, and had no personal history of tuberculosis or current household contact with someone with tuberculosis were enrolled in a safety cohort. Infants born to HIV-negative women with no personal history of tuberculosis or current household contact with a person with tuberculosis and who were 96 h old or younger, generally healthy, and had not yet received routine BCG vaccination were enrolled in a separate infant cohort. Eligible adults were randomly assigned (1:1) to receive either BCG Vaccine SSI (5 × 105 colony forming units [CFU] of Danish strain 1331 in 0·1 mL diluent) or MTBVAC (5 × 105 CFU in 0·1 mL) intradermally in the deltoid region of the arm. After favourable review of 28-day reactogenicity and safety data in the adult cohort, infants were randomly assigned (1:3) to receive either BCG Vaccine SSI (2·5 × 105 CFU in 0·05 mL diluent) or MTBVAC in three sequential cohorts of increasing MTBVAC dose (2·5 × 103 CFU, 2·5 × 104 CFU, and 2·5 × 105 CFU in 0·05 mL) intradermally in the deltoid region of the arm. QuantiFERON-TB Gold In-Tube IGRA was done on days 180 and 360. For both randomisations, a pre-prepared block randomisation schedule was used. Participants (and their parents or guardians in the case of infant participants), investigators, and other clinical and laboratory staff were masked to intervention allocation. The primary outcomes, which were all measured in the infant cohort, were solicited and unsolicited local adverse events and serious adverse events until day 360; non-serious systemic adverse events until day 28 and vaccine-specific CD4 and CD8 T-cell responses on days 7, 28, 70, 180, and 360. Secondary outcomes measured in adults were local injection-site and systemic reactions and haematology and biochemistry at study day 7 and 28. Safety analyses and immunogenicity analyses were done in all participants who received a dose of vaccine. This trial is registered with ClinicalTrials.gov, number NCT02729571. Findings: Between Sept 29, 2015, and Nov 16, 2015, 62 adults were screened and 18 were enrolled and randomly assigned, nine each to the BCG and MTBVAC groups. Between Feb 12, 2016, and Sept 21, 2016, 36 infants were randomly assigned—eight to the BCG group, nine to the 2·5 × 103 CFU MTBVAC group, nine to the 2·5 × 104 CFU group, and ten to the 2·5 × 105 CFU group. Mild injection-site reactions occurred only in infants in the BCG and the 2·5 × 105 CFU MTBVAC group, with no evidence of local or regional injection-site complications. Systemic adverse events were evenly distributed across BCG and MTBVAC dose groups, and were mostly mild in severity. Eight serious adverse events were reported in seven vaccine recipients (one adult MTBVAC recipient, one infant BCG recipient, one infant in the 2·5 × 103 CFU MTBVAC group, two in the 2·5 × 104 CFU MTBVAC group, and two in the 2·5 × 105 CFU MTBVAC group), including one infant in the 2·5 × 103 CFU MTBVAC group treated for unconfirmed tuberculosis and one in the 2·5 × 105 CFU MTBVAC group treated for unlikely tuberculosis. One infant died as a result of possible viral pneumonia. Vaccination with all MTBVAC doses induced durable antigen-specific T-helper-1 cytokine-expressing CD4 cell responses in infants that peaked 70 days after vaccination and were detectable 360 days after vaccination. For the highest MTBVAC dose (ie, 2·5 × 105 CFU), these responses exceeded responses induced by an equivalent dose of the BCG vaccine up to 360 days after vaccination. Dose-related IGRA conversion was noted in three (38%) of eight infants in the 2·5 × 103 CFU MTBVAC group, six (75%) of eight in the 2·5 × 104 CFU MTBVAC group, and seven (78%) of nine in the 2·5 × 105 CFU MTBVAC group at day 180, compared with none of seven infants in the BCG group. By day 360, IGRA reversion had occurred in all three infants (100%) in the 2·5 × 103 CFU MTBVAC group, four (67%) of the six in the 2·5 × 104 CFU MTBVAC group, and three (43%) of the seven in the 2·5 × 105 CFU MTBVAC group. Interpretation: MTBVAC had acceptable reactogenicity, and induced a durable CD4 cell response in infants. The evidence of immunogenicity supports progression of MTBVAC into larger safety and efficacy trials, but also confounds interpretation of tests for M tuberculosis infection, highlighting the need for stringent endpoint definition. Funding: Norwegian Agency for Development Cooperation, TuBerculosis Vaccine Initiative, UK Department for International Development, and Biofabri

Les vaccins conjugués

Les bactéries encapsulées (comme Haemophilus influenzae type b [Hib], Neisseria meningitidis ou Streptococcus pneumoniae) visent les ourrissons et les jeunes enfants qui, d'une part, n'ont plus d'antigènes (Ag) maternels et, d'autre part, ont un système immunitaire inefficace contre les Ag thymo-indépendants comme les polyosides capsulaires. Les vaccins polysaccharidiques conjugués transforment le polyoside en lui faisant adopter le comportement immunologique d'un Ag thymo-dépendant, ce qui permet la mise en place d'une réponse immunitaire protectrice chez le nourrisson. Là où les vaccins conjugués furent introduits dans les programmes de vaccination du nourrisson, l'incidence des infections dûes à Hib, au méningocoque du sérogroupe C, ou au pneumocoque ont chuté d'au moins 80 % : un large succès de santé publique. De plus, le suivi épidémiologique a démontré que les vaccins conjugués induisent une immunité de groupe, liée à leur effet bénéfique sur la colonisation rhinopharyngée du nourrisson. Les applications potentielles de la technologie de conjugaison à l'élargissement du nombre des sérogroupes capsulaires visés par les vaccins méningococciques ou pneumococciques sont prometteuses

Nasopharyngeal carriage of Streptococcus pneumoniae shortly before vaccination with a pneumococcal conjugate vaccine causes serotype-specific hyporesponsiveness in early infancy

BACKGROUND: The antibody response to pneumococcal conjugate vaccines (PCVs) in infants is variable. Factors responsible for this variability have not been fully elucidated. The objective of this study was to investigate whether pneumococcal carriage around the time of the first dose of 7-valent PCV (PCV7) affects serotype-specific immunologic response. METHODS: Healthy 2-month old infants were randomized to receive 2 (at the ages of 4 and 6 months) or 3 (at the ages of 2, 4, and 6 months) PCV7 doses and a booster dose (at the age of 12 months). Nasopharyngeal or oropharyngeal specimens were obtained for culture shortly before the first PCV7 dose. Serotype-specific immunoglobulin (Ig) G levels were measured at ages 2, 7, and 13 months. RESULTS: Of 545 children studied, 332 received a booster dose. The most common serotypes carried around the time of the first PCV7 dose were 6B (n = 37), 19F (n = 22), and 23F (n = 14). In carriers before the first dose, the IgG response to the carried serotype after 2 or 3 doses was significantly lower than in noncarriers. In contrast, response to the noncarried serotypes was not affected. Although all children responded to the booster dose, the response to the originally carried serotype was generally lower. CONCLUSIONS: Serotype-specific hyporesponsiveness to PCV7 after pneumococcal carriage in infants is demonstrated for the first time. This phenomenon was common, lasted for at least several months, and was only partially overcome by the 12-month booster. TRIAL REGISTRATION: isrctn.org identifier: ISRCTN28445844

A new endpoint definition improved clinical relevance and statistical power in a vaccine trial.: New endpoint formulation for vaccine trials

International audienceOBJECTIVE: Endpoints used for the evaluation of immunogenicity in vaccine trials are often the proportion of individuals with immune response or geometric means of antibody concentrations for each serotype. When a vaccine includes several types of the same species, we illustrate how an endpoint combining all responses may improve clinical relevance and statistical power. STUDY DESIGN AND SETTINGS: The motivating example was the ANRS 114 Pneumovac trial where the effect of two vaccine strategies against Streptococcus pneumoniae was assessed in adults infected by the Human Immunodeficiency Virus. The power associated with several endpoints was calculated in the example and in simulations. A new endpoint based on four ordered levels is formulated and analyzed by using a proportional odds model. RESULTS AND CONCLUSION: The analysis of this new endpoint led to an odds ratio allowing detection of improvement and detriment. In the simulation study, this endpoint was associated with the largest statistical power by increasing the amount of information used as compared with usual endpoints. We recommend this new endpoint formulation in the formal development of a new vaccination regimen, whenever applicable

Haemophilus influenzae type b polysaccharidetetanus protein conjugate vaccine does not depress serologic responses to diphtheria tetanus or pertussisantigens when coadministered in the same syringe with diphtheria-tetanus-pertussis vaccine at two four and

The safety and immunogenicity of a vaccine against Haemophilus influenzae type b consisting of purified polyribosylribitol phosphate conjugated to tetanus toxoid (PRP-T) were evaluated in 277 Chilean infants who were randomly assigned to one of three treatment groups: Group A, PRP-T mixed with diphtheria-tetanus-pertussis (DTP) vaccine in a single syringe and given as a single inoculation in one arm and placebo in the other arm; Group B, PRP-T given in one arm and DTP in the other arm; Group C, DTP given in one arm and placebo in the other. Infants were immunized at 2, 4 and 6 months of age and examined daily for 4 days after each immunization. Serum PRP antibodies; tetanus, diphtheria and pertussis antitoxin; pertussis agglutinins; and antibodies to Bordetella pertussis filamentous hemagglutinin were measured at baseline and 2 months after each dose. PRP-T was well-tolerated. After three doses of PRP-T vaccine 100% of infants attained PRP antibody concentrations ≥ 0.15 μg/ml and 96 t

Early Appearance of Bactericidal Antibodies after Polysaccharide Challenge of Toddlers Primed with a Group C Meningococcal Conjugate Vaccine: What Is Its Role in the Maintenance of Protection?

The contribution of memory responses after meningococcal vaccination to protection may depend on the rapidity of the response. Toddlers were challenged with a licensed polysaccharide (PS) vaccine 1 year after vaccination with a single dose of meningococcal group C-CRM(197) conjugate (MCC) vaccine at the age of 12 to 15 months. Bactericidal antibodies and immunoglobulin G (IgG) antibodies detected by an enzyme-linked immunosorbent assay (ELISA) were measured before challenge and 4, 7, 14, or 21 Days later (“Days” refer to treatment groups, “days” to sampling days). Among 281 subjects in the intent-to-treat population, 173 per-protocol (PP) subjects were challenged with 10 μg PS antigen and 103 others with a 50-μg PS vaccinating dose. Capsular PS-specific ELISA IgG titers were negligible in baseline samples and increased only twofold within 4 days of PS administration. In contrast, the proportion of PP subjects with serum bactericidal antibody (SBA) titers of ≥1:8 or ≥1:128 increased, respectively, from 41% and 16% before challenge to 84% and 74% at Day 4 and to 100% and 97% at Day 7. Recipients of 50 μg PS responded with similar kinetics but showed a trend toward higher antibody levels. Unexpectedly, 69% of subjects bled on days 2 to 3 already had achieved SBA titers of ≥1:8. The majority of toddlers previously immunized with MCC and challenged 1 year later with PS antigen mounted protective levels of bactericidal antibody within 2 to 4 days