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Gout is a common inflammatory joint disease worldwide, in part because the global prevalence of gout was rising.1 The direct relationship between the elevated levels of uric acid and gout attack is well-recognised. Several risk factors for gout attack are found, including dietary factors, medications and comorbidities.2 Recently, a case-crossover study conducted by Yokose et al published in Annals of the Rheumatic Diseases revealed that vaccination in the prior 2 days was associated with a twofold increased odds of gout attack when compared with no vaccine periods (adjusted OR 1.99; 95% CI 1.01 to 3.89).3 Some points not shown in the original article are discussed. In order to examine this issue in a different population, a preliminary population-based cohort study was conducted using the 2005–2012 database of the Taiwan National Health Insurance Program with 23 million people living in Taiwan.4 People ≥65 years old who had ever received an influenza vaccine were assigned as the vaccination group. People ≥65 years who never received an influenza vaccine were assigned as the non-vaccination group. In order to reduce the biassed results, people who ever had a diagnosis of gout before influenza vaccination were excluded from the study. The main outcome was a new episode of gout attack. Table 1 revealed that there was no significant difference of the incidence of gout attack between the vaccination group and the non-vaccination group (0.05 vs 0.05 per 1000 person-days; 95% CI 0.73 to 1.57, p=0.735). As stratified by sex and follow-up time, there was no significant difference of the incidence of gout attack between the vaccination group and the non-vaccination group. The universal vaccination for trivalent influenza has been initiated in people ≥65 years in Taiwan since 1998.5 In addition, the prevalence of gout was high among people ≥65 years in Taiwan (5% for men and 2.4% for women).6 To date, no systemic analysis investigated the association between influenza vaccine and gout attack. This is the reason why we focus on people ≥65 years. People receiving an influenza vaccine would be recorded in the database. Therefore, the vaccination group and non-vaccination group are less likely to be misclassified. Gout attack developing >30 days after vaccination is less likely to be related to the impact of an influenza vaccine. This is the reason why we focus on the development of gout attack within 30 days after vaccination. In this present study based on a real-world database, influenza vaccination was not associated with the risk of gout attack when compared with non-vaccination. At least, older people do not need to worry about the development of gout attack after influenza vaccination. Finally, we appreciate that Yokose et al’s study is well-conducted and provides a clear message that needs to be communicated to the readers.
Handling editor Josef S Smolen
Contributors S-WL contributed to the conception of the article, initiated the draft of the article and has approved the final draft submitted. Y-HK and K-FL conducted data analysis.
Competing interests None declared.
Provenance and peer review Not commissioned; internally peer reviewed.
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