Could Hsp be an Adverse Event Following Immunization? A Report From the Canadian Pediatric Society Immunization Monitoring Program, Active (Impact)

Abstract

Henoch Scholein purpura (HSP) is the most common vasculitis in childhood however, the definitive etiology remains to be elucidated. Some authors propose that it may be an adverse event following immunization (AEFI) as there are a some case reports and a single published case series. The success of vaccination programs relies heavily on accurate and informed vaccine safety data for counseling by health care providers. This study aims to describe the cases of HSP reported to IMPACT over the last 18 years in the context of the other literature on HSP as a possible AEFI. IMPACT has been doing active surveillance for conditions that are seen as possible AEFIs since 1991. The 12 current participating centres are located from coast to coast and account for over 90% the nation's tertiary care pediatric beds. Nurse monitors employed at each center search for admissions due to suspected or possible AEFIs within 30 days of immunization. The case definition was based on a discharge diagnosis of HSP within 30 days after an immunization. Data was collected on a standardized report form. During that period, 205 possible but unproven unusual AEFIs were reported. A total of seven cases of HSP following immunization were recorded in previously healthy children with an average age of 6.5 years (range 2-15 years); a clinical description was available for 6/7. All of the cases reported joint pain or swelling, and 5/6 reported rash. Abdominal pain or other gastrointestinal manifestations and renal manifestations were each reported in 3 cases. 3/7 cases were reported after meningococcal vaccination, and 4 after the second dose of MMR (of whom 3 also had DPT-IPV). There was a median of 2.5 days (range 1-18) between immunization and the onset of symptoms. In all cases, patients were hospitalized with a median stay of 2 days and at the time of discharge were all expected to make a full recovery although full follow up details were not available. In 3/7 cases there was an antecedent viral illnesses that may have triggered the HSP. In this small case series of HSP within one month after vaccination the age distribution and clinical presentation are consistent with the known epidemiology of HSP. The received vaccines are consistent with what children 2-15 years of age usually receive. A temporal relationship does not necessarily imply causation; at least 3/7 had viral illnesses which may have been the trigger for HSP. HSP has not been reported to follow measles, mumps or rubella disease. Further study would be required to definitely determine if these or any immunizations are associated with HSP development in susceptible hosts. Given the relatively rarity of this disease, a large prospective case control series examining the link between HSP and immunizations would be helpful.