COVID-19 Vaccination as a Trigger of IgA Vasculitis: Truth or Illusion?

To the Editor:

We read with great interest the recent article by Ramdani and colleagues in The Journal of Rheumatology on a nationwide multicenter, retrospective study conducted in France describing the status of the occurrence of IgA vasculitis (IgAV) after coronavirus disease 2019 (COVID-19) vaccination.¹ We support and appreciate the authors’ work and agree with their conclusions that IgA vasculitis following COVID-19 vaccination is usually benign and that a fortuitous link cannot be ruled out and now requires a worldwide pharmacovigilance study, but there are some concerns about some of the details in the article.

First, at the beginning of the results, the authors mentioned that 14 patients were included from 12 centers; of these, 5 were women (41.6%).¹ The median age was 52.5 years (IQR 30.75-60.5).¹ There is an error here: it should be 12 patients included in the study, not 14 patients.

Second, the incidence rate of IgAV varies across countries. A French study in 2017 applied the European Alliance of Associations for Rheumatology (EULAR)/Paediatric Rheumatology International Trials Organisation (PRINTO)/Paediatric Rheumatology European Society (PRES) criteria to homogenize the study population and found a mean annual incidence rate of approximately 30 per 100,000 people for the capture-recapture analysis.² The average annual incidence rates were 6.1 per 100,000 in the Netherlands, 6.21 to 20.4 per 100,000 in the United Kingdom, 6.79 per 100,000 in Croatia, 17.55 per 100,000 in southern Sweden, and 55.9 per 100,000 in Korea.^3,4 Is the incidence rate of IgAV after COVID-19 vaccination higher or lower than at other times (before 2020) and in other regions? Is the COVID-19 vaccine more likely to trigger IgAV than other triggers such as cold viruses, bacteria, and antibiotics? Therefore, it is recommended that the authors add a description of the incidence rate of IgAV after COVID-19 vaccination.

Third, we agree with the explanation expressed by the authors in the article regarding the causal relationship between IgAV and vaccines.¹ The authors describe that the incidence of IgAV may have decreased since the beginning of the COVID-19 pandemic.¹ Both the lockdown measures and the systematic mask-wearing in many countries may have led to a decrease in the incidence of IgAV induced by other pathogens.¹ However, it is important to note that one cannot ignore the influence of the season when looking at the decrease in IgAV incidence. The peak onset of IgAV occurs in the fall/winter season, with the lowest incidence of episodes in the summer, which is consistent with the prevalence of most respiratory infections.² The temporal pattern of IgAV attacks provides clues to trace the association between infection and the pathogenesis of IgAV.⁵ In this study,¹ is the prevalence of IgAV the same across seasons? Is the incidence of IgAV reduced by including more patients with onset in summer? Therefore, it is necessary for the authors to analyze the variability of the study population in different seasons.

Finally, we would like to thank Ramdani and colleagues again for their contributions to this study and we look forward to hearing from them.

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