Study of a Tetravalent Dengue Vaccine Administered Concomitantly or Sequentially With Adacel® in Healthy Subjects

Immunogenicity and Safety of a Tetravalent Dengue Vaccine Administered Concomitantly or Sequentially With Adacel® in Healthy Subjects Aged 9 to 60 Years in the Philippines

The aim of the study was to investigate the immunogenicity and safety of CYD dengue vaccine and Tetanus Toxoid (T), Reduced Diphtheria Toxoid (D) and Acellular Pertussis Vaccine Adsorbed (ap) (Tdap) vaccine when both vaccines were administered concomitantly or sequentially.

Primary Objectives:

• To demonstrate the non-inferiority of the humoral immune response to the Tdap booster dose concomitantly administered with the first dose of CYD dengue vaccine as compared to sequential administration, measured 28 days after Tdap booster dose.
• To demonstrate the non-inferiority of the humoral immune response to the first dose of CYD dengue vaccine concomitantly administered with Tdap as compared to sequential administration, measured 28 days after the first dose of CYD dengue vaccine.

Secondary Objectives:

• To demonstrate the non-inferiority of the humoral immune response of 3 doses of CYD dengue vaccine with the first dose concomitantly administered with Tdap as compared to sequential administration, measured 28 days after the third dose of CYD dengue vaccine.
• To describe the humoral immune response at baseline and 28 days after the first and third doses of CYD dengue vaccine, in each and any group.
• To describe the humoral immune response of Tdap vaccine at baseline and 28 days after concomitant administration with the first dose of CYD dengue vaccine as compared to the sequential administration, in each and any group.
• To describe the safety of the CYD dengue vaccine and of the Tdap booster dose after each and any injection in each group.

Participants were to receive CYD dengue vaccine according to a 3-dose schedule administered 6 months apart, with the first dose of CYD dengue vaccine administered either concomitantly or sequentially with a booster dose of the Tdap vaccine, Adacel®.

During the conduct of the study, a safety signal was identified which led to the Independent Data Monitoring Committee (IDMC) recommendation not to vaccinate participants who had never been infected by dengue prior to the first injection, i.e., dengue non-immune participants. The protocol was amended accordingly but never implemented due to absence of response of Health Authorities (HA) from The Philippines.

After having waited for more than 1.5 years, and as the participants became out of window to complete their immunization schedule and the last safety follow-up call (6 months after the last dose), the Sponsor decided to stop the trial. Participants only attended a last safety follow-up visit to terminate the study and were informed about the end of the study. As a consequence, the study was prematurely terminated before injection of the last dose (3rd dose) of the CYD dengue vaccine.

As a consequence of the IDMC recommendations, the main immunogenicity analyses were done in dengue immune participants which is not what was planned in the protocol (and this is why the primary endpoints are not exactly the same as those defined in the protocol as they were finally assessed only in dengue immune participants whereas initially it was planned to be assessed regardless of baseline status).

All participants were assessed for immunogenicity and safety. Safety assessments included solicited reactions within 7 or 14 days after each injection, unsolicited adverse events within 28 days after each injection, and serious adverse events during the study period.

Inclusion Criteria:

• Participant aged 9 to 60 years (i.e., from the day of the 9th birthday to the day prior to the 61th birthday) on the day of inclusion.
• Participant in good health, based on medical history and physical examination.
• Informed consent form (ICF) or assent form was signed and dated by the participant (based on local regulations), and/or ICF was signed and dated by the parent(s) or another legally acceptable representative (and by an independent witness if required by local regulations).
• For participant aged 9 to 11 years: known (documented) receipt of at least 4 previous doses of diphtheria toxoid, tetanus toxoid and acellular pertussis-containing (DTaP) vaccines, with the last dose not within the last 5 years prior to enrolment.

OR For participant aged at least 12 years: known (documented or self-reported) receipt of at least 3 previous doses of diphtheria toxoid, tetanus toxoid, and whole cell pertussis-containing (DTwP) vaccines, with the last dose not within the last 5 years prior to enrolment.

• Participant (or participant and parent[s]/legally acceptable representatives) was able to attend all scheduled visits and complied with all trial procedures.

Exclusion Criteria:

• Participant was pregnant, or lactating, or of childbearing potential (to be considered of non-childbearing potential, a female must be pre-menarche or post-menopausal for at least 1 year, surgically sterile, or using an effective method of contraception or abstinence from at least 4 weeks prior to the first vaccination until at least 4 weeks after the last vaccination).
• Participation at the time of study enrollment (or in the 4 weeks preceding the first trial vaccination) or planned participation during the present trial period in another clinical trial investigating a vaccine, drug, medical device, or medical procedure.
• Planned receipt of any vaccine in the 4 weeks following any trial vaccination.
• Previous vaccination against dengue disease with the trial CYD dengue vaccine.
• Receipt of immune globulins, blood or blood-derived products in the past 3 months, which might interfere with assessment of the immune response.
• Known or suspected congenital or acquired immunodeficiency (including human immunodeficiency virus (HIV) infection with impaired immune function); or receipt of immunosuppressive therapy such as anti-cancer chemotherapy or radiation therapy within the preceding 6 months; or long-term systemic corticosteroids therapy (prednisone or equivalent for more than 2 consecutive weeks within the past 3 months).
• A previous severe reaction to pertussis, diphtheria or tetanus vaccine including immediate anaphylaxis, encephalopathy within 7 days or seizure within 3 days of receiving the vaccine.
• Known systemic hypersensitivity to any of the vaccine components, or history of a life-threatening reaction to the vaccine used in the trial or to a vaccine containing any of the same substances.
• Thrombocytopenia, contraindicating IM vaccination.
• Bleeding disorder or receipt of anticoagulants within 3 weeks preceding inclusion, which might be a contraindication for IM vaccination, at the discretion of the Investigator.
• Deprived of freedom by administrative or court order, or in an emergency setting, or hospitalized involuntarily.
• Current alcohol abuse or drug addiction that, based on Investigator's judgment, may interfere with the participant's ability to comply with trial procedures.
• Chronic illness that, in the opinion of the Investigator, was at a stage where it might interfere with trial conduct or completion.
• Identified as an Investigator or employee of the Investigator with direct involvement in the proposed study, or identified as an immediate family member (i.e., parent, spouse, natural or adopted child) of the Investigator or employee with direct involvement in the proposed study.
• Self-reported HIV, Hepatitis B, or Hepatitis C infection.
• Personal history of Guillain-Barré syndrome.