Objective: To determine the coverage of childhood immunization appropriate for age among socio-economically disadvantaged recent migrants living in East China and to identify the determinants of full immunization uptake among these migrant children. Methods: This is a cross-sectional survey of 1,426 migrant mothers with a child aged ≤24 months, who were interviewed with a pretested questionnaire. Various vaccines, migration history and some other social-demographic and income details were collected. Single-level logistic regression analyses were applied to identify the determinants of full immunization status. Results: Immunization coverage rates are lower among migrants and even lower among recent migrants. The likelihood of a child receiving full immunization rise with parents’ educational level and the frequency of mother’s utilization of health care. Higher household income also significantly increase the likelihood of full immunization, as dose post-natal visits by a health worker. Conclusions: Recent migrant status favours low immunization uptake, particularly in the vulnerability context of alienation and livelihood insecurity. Services must be delivered with a focus on recent migrants. Investments are needed in education, socio-economic development and secure livelihoods to improve and sustain equitable health care services.

Objectives: This study aimed to comprehensively analyze the epidemiology of pertussis based on case characteristics and vaccination history in Zhejiang Province.Methods: We analyzed clinically diagnosed and laboratory-confirmed pertussis cases (aged 0–18 years old) reported in Zhejiang Province from January 2016 to December 2024. Vaccination history data were matched from the Zhejiang Provincial Immunization Information System.Results: A total of 63,664 pertussis cases were identified in Zhejiang Province, China. The annual incidence of pertussis among individuals aged 0–18 years increased gradually from 2016 (1.46/100,000) to 2023 (14.22/100,000), followed by a drastic surge to 512.56/100,000 in 2024. During the resurgence, incidence rose most substantially in kindergarten (3–6 years) and lower elementary (7–9 years) children, surpassing the incidence of infants in 2024. Among 55,968 identified pertussis cases with data on vaccination status, the proportion of fully vaccinated cases increased from 12.50% in 2016 to 79.24% in 2024. Among 43,004 fully vaccinated cases, kindergarten children accounted for the highest proportion (51.27%), followed by the lower elementary children (34.58%). Regarding infection timing, 68.4% of fully vaccinated cases occurred after 6 years old, whereas 31.6% occurred before 6. The median interval between last vaccine dose and disease onset was 61.45 months (interquartile range: 48.15–79.47 months).Conclusion: Our findings underscore the critical need for booster vaccination at 4–6 years, and highlight the necessity for future research to focus on vaccine safety, effectiveness, and cost-effectiveness in optimizing vaccination strategies.

Background: China has a high incidence rate of varicella yet a low coverage rate of the varicella vaccine (VarV), with safety concerns being a leading cause of the lack of vaccination willingness. This study aimed to describe VarV-related adverse events following immunization (AEFIs) and analyze their characteristics in Zhejiang, China, 2020–2022. Methods: VarV-related AEFIs in Zhejiang Province from 1 January 2020 to 31 December 2022 were collected through the Chinese National AEFI Information System (CNAEFIS) for a descriptive epidemiological analysis. Results: From 2020 to 2022, a total of 1477 VarV-related AEFI cases were reported (incidence rate: 34.79/100,000). The three most frequently reported clinical symptoms of common adverse reactions were fever, redness, and induration at the vaccination site. The distribution of VarV-related AEFIs varied significantly by age, dose, severity, and season. VarV-related AEFIs were more likely to be non-severe adverse events that occurred in the summer and winter seasons following the first dose of vaccine and among those under 3 years old. The top three regions with the highest incidence rates were Lishui City (59.53/100,000), Quzhou City (41.05/100,000), and Jinhua City (40.43/100,000). Most of the cases achieved full recovery without treatment (96.21%), and the rest were successfully treated without any sequelae. Conclusions: VarV demonstrates a safe profile in Zhejiang Province. Most VarV-related AEFIs are common reactions without requiring treatment, and the rates of rare and severe AEFIs remain low. Consistent monitoring, investigation, and diagnosis are needed to guide future VarV research and vaccination strategy adjustment. Our findings call for more policy changes, such as integrating VarV into China’s National Immunization Program and conducting more trials to evaluate the safety and effectiveness of VarV.

Background: The Haemophilus influenzae type b (Hib) vaccination has well-established safety and efficacy in preventing Hib and reducing related morbidity and mortality worldwide. China has a high disease burden of Hib yet a low coverage rate of Hib vaccines and remains the only WHO member country not including the Hib vaccine in its National Immunization Program (NIP), partly due to insufficient surveillance data on its safety. This study analyzed all adverse events following immunization (AEFIs) after Hib monovalent vaccination in Zhejiang Province from 2017 to 2023 to provide evidence for formulating relevant immunization strategies. Methods: Hib vaccine-related AEFIs in Zhejiang Province from 1 January 2017, to 31 December 2023, were collected through the Chinese National AEFI Information System (CNAEFIS) for a descriptive epidemiological analysis. Results: From 2017 to 2023, a total of 1740 Hib vaccine-related AEFIs were reported (incidence rate: 63.01/100,000 doses) (95%CI: 60.12/100,000 doses–66.04/100,000 doses), including 1577 common adverse reactions (57.10/100,000 doses) (95%CI: 54.35/100,000 doses–59.99/100,000 doses), 139 rare adverse reactions (5.03/100,000 doses) (95%CI: 4.26/100,000 doses–5.94/100,000 doses), and 24 coincidental events (0.87/100,000 doses) (95%CI: 0.58/100,000 doses–1.29/100,000 doses). Most of the AEFIs were common adverse reactions that manifested mainly as fever, injection site redness and swelling, and crying. AEFIs were more likely to occur in male participants under the age of one, in summer and autumn, and during the booster immunity stage. The top three regions with the highest reported incidence rates of AEFIs were Jiaxing City (86.61/100,000 doses) (95%CI: 74.44/100,000 doses–100.77/100,000 doses), Hangzhou City (81.29/100,000 doses) (95%CI: 72.56/100,000 doses–91.07/100,000 doses), and Taizhou City (66.62/100,000 doses) (95%CI: 58.24/100,000 doses–76.21/100,000 doses). Conclusions: Our findings provide preliminary evidence of the safety profile of the Hib vaccine at a provincial level, which adds further support for its broader implementation in other provinces. Future multi-center studies are needed to construct a comprehensive vaccine evaluation framework and make multi-criteria decisions on the feasibility of incorporating the Hib vaccine into China’s NIP.

Objective: Tetanus that occurs outside the neonatal period is not a statutory reporting disease in many regions, and few countries have comprehensive surveillance systems. To assess the level and durability of vaccine-induced tetanus immunity in a healthy population in Zhejiang, where long-term population-based data on non-neonatal tetanus immunity remain limited. Methods: A cross-sectional study was conducted in 2024 among 3,659 healthy individuals. Anti-tetanus toxoid IgG concentrations were measured by ELISA and expressed in IU/mL. Population immunity was evaluated by geometric mean concentration (GMC), seropositivity (≥0.01 IU/mL), and seroprotection (≥0.1 IU/mL). Antibody persistence was estimated according to age- and dose-specific antibody profiles. Generalized additive models (GAMs) with smoothing functions for the time since last doses were used to model nonlinear antibody trajectories overall, gender, and by dose group. Results: The overall Geometric Mean Concentration (GMC) of tetanus IgG antibodies was 0.064 IU/mL, with seropositivity (≥0.01 IU/mL) and seroprotection (≥0.1 IU/mL) rates of 85.05% and 52.94%, respectively. GMC peaked at 0.175 IU/mL in children aged 6–11 months, remained relatively high through 2 years of age, and then generally declined to 0.008 IU/mL in adults aged 40–59 years. By dose, GMC increased from 0.013 IU/mL in the 0-dose group to 0.156 IU/mL in the 3-dose group, then declined after 4 and 5 doses. Seroprotection exceeded 89% after 2–3 doses. GAM-fitted trajectories showed a rapid post-vaccination peak followed by gradual waning, with antibody levels remaining above 0.1 IU/mL for 8.81 years overall. Waning was slower in men than in women (7.87 vs. 6.66 years), and the estimated duration of seroprotection was 6.03, 12.86, and 3.07 years after three, four, and five doses, respectively. Conclusions: A high seropositivity rate does not necessarily indicate durable seroprotection against tetanus. Booster immunization strategies should incorporate both vaccination history and time since the last dose to sustain long-term protection.