Despite coverage of two doses of mumps-containing vaccines, mumps epidemics persist among children and young adults in China. This study aimed to analyze the epidemiological characteristics of mumps in Jiangsu Province, with a particular focus on breakthrough cases among high-incidence groups. Mumps cases reported in 2023 were systematically collected from the Infectious Disease Surveillance and Reporting System. A comprehensive descriptive epidemiological analysis was performed to elucidate the characteristics of the reported cases. A joinpoint regression (JPR) model was utilized to identify the temporal trends across various periods. Subsequently, immunization information for cases under 15 years of age was obtained through the Jiangsu Province Vaccination Integrated Service Management Information System to identify breakthrough cases and conduct exploratory analyses. A total of 4142 mumps cases were reported in Jiangsu Province in 2023, yielding an annual incidence rate of 4.86/100,000. A total of 81.75% of the cases were students and childcare children, and the gender ratio was 1.5:1 (male/female). The JPR model analysis of weekly reported cases identified five distinct trend segments (1st: 1–8, weekly percent change (WPC) = 26.67 *; 2nd: 9–28, WPC = 3.11 *; 3rd: 29–34, WPC = −5.31; 4th: 35–37, WPC = 15.48; 5th: 38–52, WPC = −4.06 *), and the gender subgroups demonstrated similar trends to the overall pattern. Notably, 89.14% (3692/4142) of the total cases were among individuals under 15 years, with 96.02% (3545/3692) having been vaccinated against mumps. The number of single-dose breakthrough cases (SdBCs) was approximately fourfold (2847/698) that of two-dose breakthrough cases (TdBCs). The main population composition of TdBCs was children aged 0–5 years old, and the classification was dominated by childcare children and scattered children. The median time interval between initial immunization and onset were shorter in TdBCs than in the SdBCs group, and the median time interval between the last immunization and onset was interestingly similarly shorter. However, these situations were interestingly reversed in 105 laboratory-confirmed breakthrough cases. Therefore, the current vaccination strategies have demonstrated tangible effectiveness in preventing and controlling mumps. However, the high incidence of breakthrough cases among high-risk pediatric populations indicates that mumps immunization strategies still deserve more attention and research for better herd protection.

Varicella (chickenpox) is highly contagious among children and frequently breaks out in schools. In this study, we developed a dynamic compartment model to explore the optimal schedule for varicella vaccination in Jiangsu Province, China. A susceptible-infected-recovered (SIR) model was proposed to simulate the transmission of varicella in different age groups. The basic reproduction number was computed by the kinetic model, and the impact of three prevention factors was assessed through the global sensitivity analysis. Finally, the effect of various vaccination scenarios was qualitatively evaluated by numerical simulation. The estimated basic reproduction number was 1.831 ± 0.078, and the greatest contributor was the 5–10 year-old group (0.747 ± 0.042, 40.80%). Sensitivity analysis indicated that there was a strong negative correlation between the second dose vaccination coverage rate and basic reproduction number. In addition, we qualitatively found that the incidence would significantly decrease as the second dose vaccine coverage expands. The results suggest that two-dose varicella vaccination should be mandatory, and the optimal age of second dose vaccination is the 5–10 year-old group. Optimal vaccination time, wide vaccine coverage along with other measures, could enhance the effectiveness of prevention and control of varicella in China.

Background: Influenza vaccines have been administered in Jiangsu Province. This study aimed to conduct a comprehensive retrospective analysis of influenza vaccine safety in the region from 2019 to 2023. Methods: Data were sourced from the Chinese National Adverse Events Following Immunization Information System (CNAEFIS) and Jiangsu Provincial Electronic Immunization Registries System (JSEIRS) systems. A comprehensive retrospective analysis was performed to calculate the incidence rates of adverse events following immunization (AEFI) and to identify potential safety signals through disproportionality analysis. Results: Out of 4,906,905 administered doses, 2080 AEFI cases were reported, yielding an overall incidence rate of 42.39 per 1,000,000 doses. Significantly higher rates were observed in children aged 6–35 months (71.03 per 1,000,000) and among recipients of trivalent vaccines (52.79 per 1,000,000) compared to quadrivalent vaccines (36.03 per 1,000,000). The vast majority of AEFIs were mild, common adverse reactions (94.47%, predominantly fever and local reactions), occurring predominantly within one day post-vaccination, while disproportionality analysis identified expected signals for common adverse reactions and rare local purulent infections. Conclusions: Overall, the findings affirm the vaccine’s favorable safety profile, align with pre-marketing data, and underscore the critical role of continuous post-marketing surveillance in maintaining public confidence and monitoring the safety of both established and new vaccine formulations.

Objective: to assess Chinese children’s guardians’ intentions and attitudes toward accepting a pertussis cocooning vaccination and its determinants. Methods: a self-administered questionnaire was designed based on a theoretical framework that originated mainly from the reasoned action approach. Associations between questionnaire variables and outcomes were assessed using univariate and multivariate analyses with odds ratios (OR), regression coefficients (β), and their 95% confidence intervals (CIs). Results: among 762 eligible participants, most (80.71%) reported a positive intention to accept a pertussis cocooning vaccination. The guardians’ positive intention was related to the children’s pertussis vaccination experience (OR = 2.483, 95% CI: 1.340–4.600). Guardians who had a positive attitude towards pertussis vaccination (OR = 1.554, 95% CI: 1.053–2.296), higher subjective norms (OR = 1.960, 95% CI: 1.371–2.802) and better perceived behavioral control (OR = 7.482, 95% CI: 4.829–11.591) stated a higher intention to receive a pertussis cocooning vaccination. The mean attitude score was 3.88 ± 0.863. Greater risk perception about pertussis (β = 0.390, 95% CI: 0.298–0.483), stronger obligation from moral norms (β = 0.355, 95% CI: 0.279–0.430), and good knowledge (β = 0.108, 95% CI: 0.070–0.146) were significantly related to positive attitude toward pertussis cocooning vaccination among guardians. Conclusions: Chinese children’s guardians held positive intentions and attitudes toward accepting a pertussis cocooning vaccination. The current findings described the determinants of such intention and attitude and provided knowledge based on improving guardians’ intentions for policymakers if cocooning vaccinations or related immunization strategies are implemented in China in the future.

Objectives: Varicella is a highly contagious viral disease affecting children. The SV-1 cell line-based varicella attenuated live vaccine (SV-1VarV) is the first vaccine produced using the human diploid SV-1 cell substrate. This study evaluated the real-world safety of SV-1VarV among school-aged children in Jiangsu Province, China. Methods: A retrospective descriptive study was conducted using data from the Jiangsu Provincial Immunization Program Information System and the Chinese National Adverse Event Following Immunization Information System (CNAEFIS). Children aged 7–12 years who received SV-1VarV between July 2024 and March 2025 were included. The incidence, clinical characteristics, and demographic patterns of Adverse Events Following Immunization (AEFI) were analyzed. Reporting rates were calculated per 100,000 doses. Statistical analyses included chi-square tests, Cochran–Armitage trend tests, and Poisson regression analyses (α = 0.05). Results: A total of 366 AEFI cases were reported following 1,096,117 administered doses (33.4/100,000 doses), of which 364 were adverse reactions (33.2/100,000). General reactions accounted for 97.8% (mainly fever and local reactions), and abnormal reactions accounted for 2.2% (0.73/100,000). No serious adverse events or vaccine quality-related events occurred. Adverse reaction reporting rates declined with increasing age (p < 0.001) and were higher in males than females (36.7 vs. 29.2/100,000; p = 0.001). Poisson regression indicated that older age was independently associated with a lower risk of adverse reaction reporting, whereas sex and dose number were not significantly associated. Conclusions: SV-1VarV demonstrated a favorable safety profile during large-scale use in children aged 7–12 years. Most reactions were mild, self-limiting, and consistent with expected post-vaccination responses. These findings provide robust real-world evidence supporting the continued and expanded use of SV-1VarV in school-aged children to optimize varicella immunization strategies.

Background/Objectives: Varicella is a highly contagious childhood disease that may cause severe complications in susceptible populations. The SV-1 cell line-based varicella vaccine (VarV [SV-1]) has been increasingly used in routine immunization; however, safety and reporting patterns during the transition from partial use to full Expanded Program on Immunization (EPI) implementation remain poorly characterized. This study aimed to evaluate the safety profile and reporting dynamics of VarV (SV-1) before and after its incorporation into the Expanded Program on Immunization in Jiangsu Province, China. Methods: A retrospective observational study was conducted using data from the Jiangsu Provincial Immunization Integrated Service Management Information System and the Chinese National Adverse Event Following Immunization (AEFI) Information System (CNAEFIS), including all reported AEFI following VarV (SV-1) vaccination among children under 6 years of age during 2021–2023. Temporal trends, distribution characteristics, and factors associated with AEFI reporting were assessed using descriptive analyses, negative binomial (NB) regression models, and interrupted time series (ITS) analysis. Results: A total of 1,208,500 doses of VarV (SV-1) were administered, and 634 AEFI cases were reported, corresponding to an overall reporting rate of 52.46 per 100,000 doses. Most reported events were mild, self-limiting common reactions, predominantly pyrexia and injection-site reactions. No serious adverse events were identified. Although no immediate level change was observed at EPI implementation, a significant increasing post-EPI trend was detected, consistent with enhanced surveillance sensitivity rather than a change in intrinsic vaccine safety. Abnormal reactions were rare and resolved without sequelae. Conclusions: AEFI reporting rates following VarV (SV-1) vaccination in Jiangsu Province were within expected ranges, predominantly mild and reversible. Findings support the favorable safety profile of the VarV (SV-1) in routine childhood immunization programs and provide real-world evidence to support continued implementation of the two-dose varicella vaccination strategy within the EPI.