Safety Profile of the Tetanus-Diphtheria-Acellular Pertussis Combination Vaccine as a Single Booster (5th dose) among Spanish Children Aged 4-6 years Old with Different Vaccination Schedules

Giménez-Sánchez F, García-Sicilia J, Lambermont C, Bruyere I, Qizilbash N and Marcelon L

Objective: A post-authorisation commitment to the Spanish Regulatory Agency was made to evaluate the safety of the tetanus, diphtheria and acellular pertussis vaccine Triaxis® (Tdap5) administered as a booster (5th dose) in 4-6 year old Spanish children according to the Summary of Product Characteristics (SmPC) and local vaccination guidelines. The primary objective was to determine the incidence of injection site reactions (ISRs) and systemic adverse events (sys-AEs) after Tdap5 administration. Methods: A multicentre, noninterventional, onearm cohort study with a 30-day follow-up after vaccination with Tdap5. The study was carried out by 22 primary care paediatricians in the autonomous communities (ACs) of Madrid and Andalusia, which have different vaccination schedule recommendations for the 5th dose: children are vaccinated with Tdap5 at ages 5-6 in Andalusia whereas in Madrid the vaccine is administered at age 4 coadministered with Measles, Mumps and Rubella vaccine. Adverse events (AEs) were collected by the investigator through direct assessment in the clinic immediately following vaccination and a 30-day diary card completed by parents/legal representatives. Results: A total of 553 participants were analysed; 229 (41.4%) in Madrid and 324 (58.6%) in Andalusia and follow-up was complete in 98.2%. The incidence per person-month was 4.67 for all AEs, 3.13 for adverse reactions (ARs), 2.83 for ISRs, 3.52 for solicited AEs, 0.78 for unsolicited AEs and 1.31 for sys-AEs. The incidence of serious adverse events (SAEs) was 0.005 per person-month, based on three cases of which two (Syncope and Type III hypersensitivity reaction) were considered vaccine-related and all recovered. The most frequent reactions were ISRs: pain, 67.3%; inflammation, 35.5%; erythema, 38.9%. Conclusions: The results confirm the expected safety profile of Tdap5 in routine clinical practice when administered in 4-6 year old Spanish children. No safety signal has been identified and the safety profile of Tdap5 is consistent with the SmPC.