{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,21]],"date-time":"2026-07-21T06:05:13Z","timestamp":1784613913835,"version":"3.55.0"},"reference-count":32,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,7,21]],"date-time":"2026-07-21T00:00:00Z","timestamp":1784592000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100017594","name":"Medical Science and Technology Project of Zhejiang Province","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100017594","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>To evaluate the vaccine effectiveness (VE) of single-dose and two-dose varicella vaccine (VarV) among senior high school students during a varicella outbreak in China, and provide recommendations for vaccination strategy optimization.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      A retrospective cohort study was conducted among students in a senior high school in China during a varicella outbreak from July 23 to November 8, 2024. The history of varicella disease, the immunization history of VarV and the incidence during the outbreak among all students in the school were surveyed. Kaplan\u2013Meier methods were used to estimate the cumulative varicella-free survival rate among students with different immunization histories during the outbreak, and the log-rank test was used to compare the survival curves across the five groups. VE was calculated based on attack rates among students with different vaccination doses and intervals since last vaccination. Post-exposure vaccination VE was also assessed. Logistic regression analysis was performed to identify factors associated with varicella infection during the outbreak, and odds ratio (OR) and 95% confidence interval (95%\n                      <jats:italic>CI<\/jats:italic>\n                      ) were calculated.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      Among the 1,862 students present during the outbreak, the overall varicella attack rate was 6.29%. Kaplan\u2013Meier analysis showed significant differences in cumulative varicella-free survival among the different immunization groups (\n                      <jats:italic>\u03c7<\/jats:italic>\n                      \u00b2 = 297.913,\n                      <jats:italic>df<\/jats:italic>\n                      \u00a0=\u00a04,\n                      <jats:italic>P<\/jats:italic>\n                      \u00a0&amp;lt;\u00a00.001). Single-dose varicella vaccine (VarV) coverage was 28.24% (475\/1682), and two-dose coverage was 66.23% (1114\/1682). Compared with unvaccinated individuals, VE with 95%\n                      <jats:italic>CI<\/jats:italic>\n                      was 32.14% (\u221254.37%- 70.17%) for 1-dose recipients and 94.74% (88.62%-97.57%) for 2-dose recipients. Among 1-dose recipients, VE was 90.48% (17.22%-98.90%) and 18.68% (\u221286.86%- 64.61%) for those with an immunization interval \u226410 years and &amp;gt;10 years, respectively. Among 2-dose recipients, VE was 95.94%(90.69%-98.23%) and 92.89%(83.87%-96.87%) for those with an immunization interval \u22646 years and &amp;gt;6 years, respectively. Logistic regression showed that male students had a higher risk of varicella than female students; prior receipt of two doses of VarV significantly reduced the risk of infection; and the risk increased by 1 year for each additional year between the last immunization and exposure to the index case. The VE of post-exposure vaccination was 90.15% (68.53%-96.92%) among unvaccinated students and 94.88% (89.47%-97.51%) among students who had previously received 1 dose.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>A single dose of varicella vaccine provides limited long-term protection among high school students, whereas a two-dose regimen offers robust and sustained effectiveness. Routine catch-up vaccination and timely post-exposure vaccination are recommended for the effective control of varicella outbreaks in school settings.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fimmu.2026.1847492","type":"journal-article","created":{"date-parts":[[2026,7,21]],"date-time":"2026-07-21T05:35:43Z","timestamp":1784612143000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Effectiveness of varicella vaccine during a varicella outbreak in a Chinese senior high school: a retrospective cohort study"],"prefix":"10.3389","volume":"17","author":[{"given":"Nani","family":"Xu","sequence":"first","affiliation":[{"name":"Department of Immunization Program, Xihu District Center for Disease Control and Prevention(Xihu District Health Inspection)","place":["Hangzhou, 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