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WHO position paper on varicella vaccines – November 2025
On November 21, the World Health Organization (WHO) released the latest Varicella Vaccine Position Paper in its Weekly Epidemiological Record. The document was revised on the basis of the WHO Strategic Advisory Group of Experts on Immunization (SAGE) review of updated evidence at its March meeting this year, and it replaces the 2014 position paper.
Key updates in this position paper include:
- In settings where varicella constitutes a significant public health problem, WHO recommends considering a two-dose vaccination schedule (with a minimum interval of 4 weeks between doses) for the prevention of varicella in children. The first dose may be administered from 9 months of age and, if a combination vaccine is not used, can be given concomitantly with the first dose of measles vaccine. Catch-up vaccination for adolescents and adults should also follow a two-dose varicella vaccine schedule.
- In countries that have implemented national varicella immunization programs, no shift of varicella infection to older age groups has been observed. To avoid the theoretical risk of delayed age of infection resulting from low or moderate coverage, countries introducing varicella vaccination should aim to achieve high vaccination coverage at both national and subnational levels. Countries should define their own minimum coverage targets based on criteria such as national and regional disease burden, affordability, cost-effectiveness, seroprevalence, and the typical age of infection acquisition.
- The position paper recommends considering varicella monovalent vaccination for special populations, including certain groups at increased risk of severe disease. Immunocompromised individuals, as well as people living with HIV who are well controlled and have adequate CD4 cell counts (>200 per µl), may receive a two-dose regimen of varicella monovalent vaccine.
Source: https://iris.who.int/server/api/core/bitstreams/473b51ee-a798-4501-8990-6b353760ccaa/content
Journal Articles Recommendation
01
Ranking the most efficient human papillomavirus vaccination strategies in low-income and lower-middle income countries: a mathematical modelling analysis
This study was published in The Lancet Global Health and aimed to identify the most efficient HPV vaccination strategies to maximize reductions in cervical cancer burden in low- and lower-middle-income countries under conditions of constrained vaccine supply. The research team applied the HPV-ADVISE mathematical model to systematically simulate and compare 162 vaccination strategies across 67 countries.
Strategy parameters included target populations (girls/women only versus gender-neutral vaccination), age groups (routine vaccination at age 9, with catch-up vaccination extending to ages 14, 20, 25, 30, and 35), number of doses (one dose or two doses), and vaccination coverage levels (40%–90%). Efficiency was assessed using the “number needed to vaccinate” (NNV), defined as the number of vaccine doses required to prevent one case of cervical cancer, and all strategies were ranked accordingly.
Under the base-case scenario (80% coverage, one-dose vaccine effectiveness assumed to be non-inferior to two doses, and limited potential to further increase coverage), model results showed that, on the basis of routine one-dose vaccination of 9-year-old girls, the most efficient sequence of strategies was one-dose multi-age cohort catch-up vaccination for girls aged 10–14 years (NNV 48), followed by one-dose catch-up vaccination for girls aged 15–20 years (NNV 64), two-dose catch-up vaccination for women aged 21–25 years (NNV 369), routine and catch-up vaccination for boys aged 9–20 years (NNV 512), and finally two-dose catch-up vaccination for women aged 26–30 years and 31–35 years. Across all scenarios, the model consistently indicated that the most efficient strategy was one-dose vaccination covering girls younger than 20 years. The study further noted that subsequent strategy choices were highly context-dependent: in countries with high cervical cancer incidence or limited capacity to increase coverage, including boys in vaccination programs was more efficient; whereas in countries able to achieve high coverage (up to 90%), prioritizing vaccination of older women (up to 35 years) would prevent more cervical cancer cases than extending vaccination to boys.
Overall, the study provides a clear decision pathway for resource-limited countries: priority should be given to expanding one-dose HPV vaccination coverage among girls aged 9–20 years and maximizing uptake, followed by context-specific consideration of extending vaccination to boys or adding a second dose, in order to advance cervical cancer elimination through optimal allocation of limited resources.
https://doi.org/10.1016/S2214-109X(25)00376-6
02
Immunogenicity and safety of varicella vaccine co-administered with seasonal influenza vaccine in healthy children aged 7-12 years in China
This study, conducted by Sun Xiang, Wang Zhiguo, and colleagues and published in the International Journal of Infectious Diseases, aimed to evaluate the immunogenicity and safety of concomitant administration of the live attenuated varicella vaccine and the trivalent seasonal inactivated influenza vaccine in healthy Chinese children aged 7–12 years, compared with separate vaccination schedules.
The study was carried out in Jiangsu Province using an open-label, randomized, controlled trial design. A total of 899 healthy children without a history of varicella were enrolled and randomly assigned in a 1:1:1 ratio to receive the varicella vaccine alone, the influenza vaccine alone, or concomitant vaccination. Serum samples were collected at baseline and 30 days post-vaccination. Varicella antibody titers were measured using the fluorescent antibody to membrane antigen (FAMA) assay, while antibody responses to each strain in the trivalent influenza vaccine were assessed using the hemagglutination inhibition (HI) assay. Local and systemic adverse events were actively monitored and recorded within 30 days after vaccination.
Immunogenicity analyses showed that the immune response to the varicella vaccine was comparable between the concomitant and separate administration groups. The geometric mean titers (GMTs) were 66.67 in the concomitant vaccination group and 63.82 in the varicella-only group, yielding a GMT ratio of 1.04 (95% CI: 0.86–1.26), which met the predefined non-inferiority criterion. Seropositivity rates were ≥98% in both groups, and seroconversion rates were approximately 91%, with no statistically significant differences between groups. For the influenza vaccine, immune responses to all three influenza strains (A/H1N1, A/H3N2, and B/Victoria) in the concomitant vaccination group were non-inferior to those observed with influenza vaccination alone, with all strains meeting non-inferiority criteria.
In terms of safety, concomitant vaccination did not increase the risk of adverse events. The overall incidence of adverse events was 8.35%, and the incidence of vaccine-related adverse events was 3.67%, with no statistically significant differences among groups. Most adverse events were mild local reactions, such as injection-site pain, redness, or induration. No vaccine-related serious adverse events were reported during the study period.
In conclusion, concomitant administration of the varicella vaccine and the trivalent influenza vaccine in healthy children aged 7–12 years demonstrated good safety and immunogenicity and was non-inferior to separate administration. Given that catch-up varicella vaccination and seasonal influenza vaccination often overlap in timing in China, promoting concomitant vaccination strategies could reduce the number of clinic visits required by caregivers and improve overall immunization coverage among children.
https://doi.org/10.1016/j.ijid.2025.108212
03
Influenza vaccination for prevention of death and major cardiovascular events in patients with a history of stroke: A subanalysis of the VIP-ACS trial
This study, published in the International Journal of Stroke, aimed to evaluate the effectiveness of administering a double-dose influenza vaccine during hospitalization in preventing major adverse cardiovascular events (MACE) among patients with a prior history of stroke following acute coronary syndrome (ACS). The study was a prespecified subgroup analysis of the VIP-ACS trial and adopted a randomized, open-label, multicenter design with blinded endpoint assessment.
Adult patients hospitalized with ACS within 7 days of symptom onset were randomly assigned to receive either a double-dose quadrivalent inactivated influenza vaccine during hospitalization or a standard-dose influenza vaccine 30 days after randomization. The primary composite endpoint included all-cause mortality, myocardial infarction, stroke, unstable angina, hospitalization for heart failure, urgent coronary revascularization, and hospitalization for respiratory diseases. Outcomes were analyzed using the win ratio (WR) method. Patients were followed for 12 months during each influenza season.
A total of 1,801 hospitalized ACS patients were included (31% women), of whom 67 had a prior history of stroke. Among patients without a history of stroke, no significant difference in the primary composite endpoint was observed between the double-dose and standard-dose groups (win rates 11.4% vs. 12.1%; WR 0.94, 95% CI 0.72–1.24; P = 0.69). In contrast, among patients with a prior stroke, significant benefit was observed with in-hospital double-dose vaccination (win rates 43.9% vs. 16.8%; WR 2.62, 95% CI 1.10–6.25; P = 0.03). Consistent results were seen for the MACE composite endpoint, with the double-dose group also demonstrating superior outcomes (win rates 41.3% vs. 13.7%; WR 3.01, 95% CI 1.15–7.88; P = 0.02).
The study indicates that, in patients with a prior history of stroke who experience ACS, administration of a double-dose influenza vaccine during hospitalization is more effective than standard-dose vaccination in reducing death and major cardiovascular and cerebrovascular events over a 12-month period.
The win ratio (WR) method is a clinically oriented statistical approach that prioritizes more severe events, providing a more sensitive and clinically meaningful evaluation of composite endpoints that include outcomes of differing clinical importance.
https://doi.org/10.1177/17474930251383626
04
Association between seasonal influenza vaccination and neonatal outcomes in Shanghai, China
This study, conducted by Shanghai United Family Hospital in collaboration with the Changning District Center for Disease Control and Prevention and published in Human Vaccines & Immunotherapeutics, aimed to evaluate the association between seasonal influenza vaccination during pregnancy and neonatal health outcomes using real-world data from Shanghai, China. The study sought to address persistently low maternal influenza vaccination uptake in China, largely driven by concerns about fetal safety.
A retrospective cohort design was employed, including 2,517 pregnant women who were registered and delivered at an international hospital in Shanghai between August 2020 and July 2023. Among them, 203 women (8.1%) received a seasonal influenza vaccine during pregnancy. Using Poisson regression and logistic regression models, the study systematically compared neonatal outcomes between vaccinated and unvaccinated groups after adjustment for potential confounders, including infant sex, maternal age, pre-pregnancy body mass index, and parity. Neonatal outcomes assessed included small for gestational age (SGA), large for gestational age (LGA), preterm birth (PTB), low birth weight (LBW), low Apgar score, congenital anomalies, neonatal intensive care unit (NICU) admission or referral, and stillbirth or neonatal death.
The results showed no statistically significant associations between influenza vaccination during pregnancy and increased risks of any assessed adverse neonatal outcomes. The adjusted risk ratios (95% CI) were 1.354 (0.842–2.177) for SGA, 1.504 (0.808–2.798) for LGA, 0.639 (0.257–1.590) for PTB, 0.294 (0.072–1.211) for LBW, 0.918 (0.213–3.958) for low Apgar score, 0.676 (0.087–5.247) for congenital anomalies, and 0.151 (0.021–1.089) for NICU admission or referral. In addition, one stillbirth and one neonatal death were observed in the unvaccinated group, corresponding to a cumulative incidence of 0.1%, whereas no such severe outcomes were reported in the vaccinated group.
Overall, the study found no evidence that seasonal influenza vaccination during pregnancy increased the risk of adverse neonatal outcomes among pregnant women in Shanghai. These findings provide important real-world safety evidence to support public health efforts aimed at increasing influenza vaccination coverage among pregnant women in China.
https://doi.org/10.1080/21645515.2025.2583804
Content Editor: Tianyi Deng
Page Editor: Ruitong Li
