Background/Purpose: The etiology of IgA vasculitis (Henoch–Schönlein, IgAV), the most common systemic vasculitis in children, is unknown, although seasonality in disease onset and clinical observation strongly suggest an etiopathogenic link with preceding infectious episodes. There is also some concern that IgAV may occur after vaccination. Thus, the evidence for the relationship between vaccination and IgAV is essentially based on case reports, and robust pharmacoepidemiological data (e.g., from case–control studies) are lacking. We performed a case-crossover study, a variant of a traditional case–control study in which each case serves as its own control, to investigate the effect of vaccination on short-term risk of IgAV.

Methods: The study enrolled children (≤17 years old) with newly or previously diagnosed IgAV fulfilling the EULAR/PReS classification criteria and who were seen in 4 pediatric hospitals from 2011 to 2016. Data on vaccinations administered during the 12 months before IgAV onset were retrieved from the children’s immunization records. With a case-crossover analysis, we calculated odds ratios (OR) on conditional logistic regression by comparing exposure to vaccination in the 3-month “index period” immediately preceding disease onset with exposure in 3 consecutive 3-month “control” periods immediately before the “index period”. A minimal sample size of 150 children was determined to detect a statistically significant OR ≥2.5 under the assumption of a baseline exposure to vaccines of 5% in each 3-month control period. On sensitivity analyses, we used 1 or 2-month windows for the index and control periods.

Results: We enrolled 167 children with IgAV (mean age 6.7 years, 52% boys) for whom complete information on vaccine exposure could be obtained; 42 (25%) received ≥1 vaccination during the 12 months before IgAV onset. The total recorded 54 vaccine doses mainly involved diphtheria-tetanus-pertussis-poliomyelitis (n=14), diphtheria-tetanus-poliomyelitis (n=12), hepatitis A (n=8), meningococcal (n=7), and measles-mumps-rubella vaccines (n=5). Fifteen children (9%) were vaccinated during the 3-month index period as compared to 4% to 7% in the 3 control periods. The OR for IgAV within 3 months of a vaccination was 1.6 (95%: CI 0.8–3.0). Analyses based on IgAV risk within 1 or 2 months of vaccination yielded ORs of 1.4 (95% CI: 0.5–3.5) and 1.3 (95% CI: 0.6–2.6), respectively. Seasonal distribution of IgAV onset was 25%, 35%, 26% and 13% for fall, winter, spring and summer, respectively; the corresponding proportions for seasonal distribution of vaccine administration were 28%, 28%, 13% and 32%.

Conclusion: This study does not support vaccination as a major etiological factor of childhood IgAV.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/vaccination-and-risk-of-childhood-iga-vasculitis-henoch-schonlein-a-case-crossover-analysis/