Vaccination coverage, immune responses, and clinical characteristics in children with PFAPA syndrome: a monocentric prospective study

PFAPA syndrome (Periodic Fever, Aphthous Stomatitis, Pharyngitis, and Adenitis) is the most common periodic fever condition in children. Vaccination in this population can be challenging due to concerns about immune hyperreactivity, the potential to trigger febrile episodes, and uncertainty regarding vaccine efficacy. Data on immunization coverage and vaccine response in PFAPA remain limited. This study aimed to describe the clinical characteristics of children with PFAPA, with a particular focus on vaccination coverage and serological responses. We conducted a prospective study of children with PFAPA followed at Geneva University Hospitals between February 2022 and April 2025. Clinical, laboratory, and genetic data were collected, along with vaccination status according to the Swiss national immunization schedule and serological results for major vaccine antigens. Forty-one patients were included. All exhibited elevated inflammatory markers during febrile episodes, and none had a monogenic cause identified. Vaccination coverage was high, with 90–95% of patients receiving the primary DTaP-IPV-Hib-HBV series on time. Minor delays were observed for the third pneumococcal and second MMR doses. Meningococcal (MenC/MenACWY) vaccination was administered on time in 58% of patients. Serological testing confirmed protective antibody levels for most antigens, including diphtheria, tetanus, and measles, but only 40% achieved protective pneumococcal titers. Only 65% showed varicella immunity because of past infection, as none had received the vaccine, which was only introduced in Switzerland in 2023. Children with PFAPA demonstrate high adherence to vaccination schedules and adequate immune responses, supporting the safety and effectiveness of routine immunization in this group. The reduced pneumococcal seroprotection suggests that monitoring antibody levels and considering booster doses may be warranted. Larger controlled studies are needed to assess vaccine immunogenicity and reactogenicity, particularly for highly reactogenic vaccines such as meningococcal B.