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October 13, 2025Iranian Journal of Public HealthOpen Access

Primary infection with EV71 was associated with a significantly higher risk of hand, foot and mouth disease reinfection (OR 1.83) compared to non-reinfection cases.

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Why the study?

Because the absence of cross-protection against different enterovirus sub-types makes hand, foot and mouth disease reinfection common, this study aimed to explore its epidemiological characteristics and influencing factors in Qingdao City.

Population

78422 HFMD cases from 2014 to 2022 in Qingdao City

Comparison

Reinfection cases vs non-reinfection cases

Design

Observational surveillance registry analysis

Key result

Primary infection with EV71 was associated with a significantly higher risk of hand, foot and mouth disease reinfection (OR 1.83) compared to non-reinfection cases.

Authors

XXXueling XinJJJing JiaHZHongrui Zhai

Discussion

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Overview

Identifies risk factors for HFMD reinfection; hypothesis-generating and requires prospective validation before guiding prevention.

Key Points

  • To characterize the epidemiological patterns and identify independent risk factors associated with hand, foot, and mouth disease reinfection.
  • Analyzed hand, foot, and mouth disease case records (N=78,422) reported between 2014 and 2022 from the National Infectious Surveillance System in Qingdao, China.
  • Conducted multivariable logistic regression analysis to identify independent demographic and clinical risk factors for reinfection.
  • Reinfection occurred in 2,041 of 78,422 patients (reinfection rate of 2.60%), with a median interval between infections of 12.75 months (IQR=12.24) and seasonal peaks from June to August.
  • Primary infection with EV71 was significantly associated with higher odds of reinfection compared to non-reinfection cases (OR=1.83, 95% CI=1.29–2.60).
  • Male sex, younger age, scattered child status, severe disease manifestation, and hospital admission were identified as independent risk factors for reinfection.

Study Design

Type

Observational (n=78,422)

Structured PICO

P
Population
78,422 patients with hand, foot and mouth disease in Qingdao, China, were evaluated between 2014 and 2022 to identify epidemiological characteristics and risk factors for reinfection.
O
Outcome
HFMD reinfection

Main Result

Odds Ratio: 1.83 (95% CI 1.29–2.6)

Absolute Event Rate: 31.79% vs 20.72%

p-value: p=0.001

Boys aged 5 years and below, especially those with severe cases and first infected with EV71, are more prone to HFMD reinfection, highlighting the need for targeted interventions.

Limitations

  • Potential under-reporting as cases were mainly reported by medical institutions
  • Lack of clinical and vaccine information in the National Infectious Surveillance System data
  • Findings based on data from Qingdao may not be generalizable to other cities
  • Potential misclassification of non-reinfection cases if reinfection occurred outside the study period
  • Mild cases might not seek medical attention leading to under-reporting
  • National Infectious Surveillance System lacks clinical and vaccine information
  • Single city study (Qingdao) may not be generalizable
  • Possible misclassification of non-reinfection cases if reinfection occurred outside study period

Cite This Study

Xin et al. (2025) conducted an observational in Hand, foot and mouth disease (HFMD) (n=78,422). EV71 infection vs. Non-reinfection cases was evaluated on HFMD reinfection (OR 1.83, 95% CI 1.29-2.60, p=0.001). Primary infection with EV71 was associated with a significantly higher risk of hand, foot and mouth disease reinfection (OR 1.83) compared to non-reinfection cases.

synapsesocial.com/papers/6a8abd0193d6d5583ccc207dhttps://doi.org/10.18502/ijph.v54i9.19859
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Also Consider

Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context:

  1. 1Epidemiological Characteristics of Hand, Foot and Mouth Disease Reinfection in Guangzhou, Southern China from 2012 to 20172022 · 2 citations
  2. 2Epidemiological characteristics of hand, foot and mouth disease reinfection in Guangzhou, Southern China from 2012 to 20172019 · 1 citations
  3. 3Epidemiological characteristics and influential factors of hand, foot and mouth disease (HFMD) reinfection in children in Anhui province2015 · 28 citations
  4. 4Epidemiological characteristics and influencing factors of hand, foot and mouth disease reinfection cases in a large district of southern China2026
  5. 5A Meta-Analysis of Influencing Factors for Reinfection of Hand, Foot and Mouth Disease in China, Based on Adjusted Effect Estimates2026