Objective : To analyze the epidemiological characteristics of pertussis among the population aged ≤18 years in Zhejiang Province from 2016 to 2023, so as to provide a basis for optimizing pertussis prevention and control measures as well as immunization strategies. Methods: Data on pertussis cases among individuals aged ≤18 years in Zhejiang Province from 2016 to 2023 were collected through the Infectious Disease Reporting Information System of Chinese Disease Prevention and Control Information System. Vaccination records were obtained from the specialized pertussis epidemiological survey conducted in Zhejiang Province. The descriptive epidemiological method was employed to analyze the epidemiological characteristics of pertussis among the population aged ≤18 years, as well as the interval between disease onset and the last immunization among breakthrough cases. Results: A total of 7 431 pertussis cases aged ≤18 years were reported in Zhejiang Province from 2016 to 2023, with an average annual reported incidence of 8.68/105. The overall trend showed no statistical significance (P>0.05). The reported incidence remained relatively low from 2016 to 2021, consistently below 10.00/105. In contrast, the incidence rose to 33.98/105 in 2022 and 13.39/105 in 2023. The peak incidence period was from April to August, during which 4 024 cases were reported, accounting for 54.15%. Hangzhou City, Wenzhou City, and Ningbo City reported the highest number of cases, with 3 844, 1 581, and 646 cases, representing 51.73%, 21.28%, and 8.69%, respectively. In terms of average annual incidence, Hangzhou City, Wenzhou City, and Huzhou City ranked the highest, with rates of 33.98/105, 12.38/105, and 12.27/105, respectively. Among age groups, the highest reported incidence was observed in children aged 0-<1 years, at 48.87/105. From 2016 to 2023, the incidence in the 5-<10 years and 10-18 years age groups showed upward trends (AAPC=108.193%, 106.709%, both P<0.05). The proportion of cases in the 5-<10 years age group also increased during this period (P<0.05). A total of 109 breakthrough pertussis cases were identified. The median interval between disease onset and the last immunization was 4.00 (interquartile range, 4.00) years. The numbers of cases with intervals of 1-<2 years and ≥6 years were both relatively high, comprising 25 cases and 37 cases, which accounted for 22.94% and 33.94%, respectively. Conclusions From 2016 to 2021, the reported incidence of pertussis in Zhejiang Province remained relatively stable. However, a sharp increase was observed in 2022. The disease peaked during spring and summer. Key populations for targeted prevention and control included children aged 0-<1 year, 5-<10 years, and 10-18 years. The interval between disease onset and the last immunization among breakthrough pertussis cases exhibited a bimodal distribution.

The morbidity and mortality associated with diphtheria have been effectively managed through mass immunization strategies. Nevertheless, recent outbreaks of diphtheria have been reported in various regions of Africa and Asia. In addition to infections among children, there has been a notable increase in cases among middle-aged and elderly individuals, underscoring the necessity of continued vigilance in the control of diphtheria. This paper reviewed the epidemiology of diphtheria, the current application of vaccines, and immunization strategies, with the aim of providing evidence for the prevention and control of this disease.

Immunization represents the most effective strategy for the prevention and control of diseases. Nevertheless, some people may still get infected and contract the disease even after being fully vaccinated, which is known as a "breakthrough case." The presence of breakthrough cases shows that although vaccines significantly lower the rates of disease and death, they do not entirely eliminate the risk of illness.Addressing breakthrough cases, comprehending their epidemiological characteristics, and identifying the associated factors carry substantial public health implications for vaccine development, the optimization of vaccination strategies, and the implementation of intervention efforts. This review aims to provide a scientific reference for enhancing the prevention and control of vaccine-preventable diseases by summarizing the definitions, epidemiological characteristics, and relevant factors related to breakthrough infection cases across various diseases.

Objective:To analyze the epidemiological and clinical characteristics of pertussis cases identified through active surveillance.Methods:Active surveillance for pertussis was conducted in three sentinel hospitals in Yiwu, Zhejiang Province, and Yongcheng, Henan Province. The study population included cases that met the surveillance case definition and sought medical care at outpatient/emergency departments or were hospitalized between June 1, 2021, and May 31, 2022. Samples were collected for bacterial culture and PCR detection. Case information and clinical data were collected. Differences in rates were assessed using the chi-square test or Fisher's exact probability test, and the differences in cough time were compared using the Mann-Whitney U test. Results:Among 1 423 cases of pertussis surveillance, the positive rate of pertussis was 28.11% (400/1 423), with a median age of 5 years (interquartile range: 2, 8). The positive rate in Yongcheng, Henan Province, and Yiwu, Zhejiang Province were 39.27% (216/550) and 21.08% (184/873), respectively; the positive rate of pertussis was highest in July 2021, and the highest positive rate of pertussis was among those aged 10-14. The positive rate of pertussis in hospitalized cases was higher than in outpatient/emergency cases (26.68%) ( χ2=4.16, P=0.041). Among the 400 laboratory test-positive cases, the highest proportion of atypical symptom cases was in adults aged 20-59 (43.33%, 13/30). The specificity rates of apnea and worsening nocturnal cough in monitored cases under 3 months of age were 100.00% and 73.81%, respectively. Among monitored cases aged 3 months to 9 years, the proportions of symptoms including worsening nighttime cough (63.00%) and night sweats (4.59%) in test-positive cases were significantly higher than those in the test-negative group (47.77% and 0.56%, respectively), with statistically significant differences (both P<0.05). The specificity rates of worsened nighttime coughing and night sweats were 52.23% and 99.44%, respectively. Conclusions:The active surveillance results for pertussis showed that the 10-14 age group exhibited the highest positivity rate. Active surveillance enhanced the detection rate of pertussis. Among laboratory-confirmed cases, the proportion of atypical symptoms was the highest in adults, suggesting that laboratory testing should be combined to diagnose programs of pertussis. For infants under 3 months, worsening nighttime cough and apnea increase the diagnostic specificity, while for individuals aged 3 to 9 years old, worsening nighttime cough and night sweats increase the diagnostic specificity.

Abstract In April 2021, type Ⅰ vaccine-derived poliovirus (VDPV) was detected from two fecal samples of a male infant with acute flaccid paralysis (AFP) in Zhejiang Province when he was admitted to the Children's Hospital Affiliated to Fudan University in Shanghai, with 12 and 14 nucleotide mutations in the VP1 region, respectively. The case had a history of immunization with three doses of poliovirus vaccines, and grade Ⅲ proximal muscle strength and grade Ⅱ distal muscle strength of the right lower limb. After symptomatic treatment, the activity of the right lower limb and the muscle strength was significantly restored, thus he was discharged. VDPV was not detected from subsequent (the 8th to 12th) fecal samples of the case and fecal samples of close contacts. No similar cases were found in medical institutions in the county, surrounding areas, neighboring villages or towns. Since the case did not exhibit clinical symptoms of poliomyelitis caused by VDPV, poliomyelitis was excluded, and the case was diagnosed with hemophilia type A based on the epidemiological investigation, laboratory tests, and the history of poliomyelitis vaccination. This event involved cross-provincial (municipal) cooperation and was responsed promptly, preventing further spread of the virus. It suggested that the sensitivity of the AFP case surveillance system should be maintained, environmental monitoring methods should be increased, and the poliomyelitis vaccination should be promoted to prevent the spread of the virus.

Objective:To analyze the epidemiological and clinical characteristics of pertussis cases identified through active surveillance.Methods:Active surveillance for pertussis was conducted in three sentinel hospitals in Yiwu, Zhejiang Province, and Yongcheng, Henan Province. The study population included cases that met the surveillance case definition and sought medical care at outpatient/emergency departments or were hospitalized between June 1, 2021, and May 31, 2022. Samples were collected for bacterial culture and PCR detection. Case information and clinical data were collected. Differences in rates were assessed using the chi-square test or Fisher's exact probability test, and the differences in cough time were compared using the Mann-Whitney U test. Results:Among 1 423 cases of pertussis surveillance, the positive rate of pertussis was 28.11% (400/1 423), with a median age of 5 years (interquartile range: 2, 8). The positive rate in Yongcheng, Henan Province, and Yiwu, Zhejiang Province were 39.27% (216/550) and 21.08% (184/873), respectively; the positive rate of pertussis was highest in July 2021, and the highest positive rate of pertussis was among those aged 10-14. The positive rate of pertussis in hospitalized cases was higher than in outpatient/emergency cases (26.68%) ( χ2=4.16, P=0.041). Among the 400 laboratory test-positive cases, the highest proportion of atypical symptom cases was in adults aged 20-59 (43.33%, 13/30). The specificity rates of apnea and worsening nocturnal cough in monitored cases under 3 months of age were 100.00% and 73.81%, respectively. Among monitored cases aged 3 months to 9 years, the proportions of symptoms including worsening nighttime cough (63.00%) and night sweats (4.59%) in test-positive cases were significantly higher than those in the test-negative group (47.77% and 0.56%, respectively), with statistically significant differences (both P<0.05). The specificity rates of worsened nighttime coughing and night sweats were 52.23% and 99.44%, respectively. Conclusions:The active surveillance results for pertussis showed that the 10-14 age group exhibited the highest positivity rate. Active surveillance enhanced the detection rate of pertussis. Among laboratory-confirmed cases, the proportion of atypical symptoms was the highest in adults, suggesting that laboratory testing should be combined to diagnose programs of pertussis. For infants under 3 months, worsening nighttime cough and apnea increase the diagnostic specificity, while for individuals aged 3 to 9 years old, worsening nighttime cough and night sweats increase the diagnostic specificity.

Objective:To evaluate the protective effectiveness (VE) of the acellular pertussis vaccine (aPV) against pertussis in children aged 2 months to 6 years.Methods:A test-negative case-control study was conducted among children aged 2 months to 6 years who sought medical care for cough and underwent pertussis nucleic acid testing at sentinel surveillance hospitals in Zhejiang Province in 2024. Cases were defined as those with positive pertussis nucleic acid test results, while controls were test-negative individuals matched 1∶1 based on propensity scores using the caliper matching method. Conditional logistic regression models were used to calculate odds ratios ( ORs) and VEs. Results:Among the 658 participants, 31.76% (209 cases) tested positive for pertussis. After propensity score matching, 203 cases and 203 controls were included in the analysis. The VE of 1-2, 3, and 4 doses of aPV against pertussis was 52.46% (95% CI:-39.82%-83.84%), 65.22% (95% CI: 6.86%-87.02%), and 72.21% (95% CI: 34.33%-88.24%), respectively. For pertussis-related hospitalization, the VE of 1-3 and 4 doses was 80.95% (95% CI:31.38%-94.71%) and 86.79% (95% CI: 51.89%-96.37%). The VE for those who completed 4 doses of vaccination and had intervals of less than 2 years, 2 years, 3 years, and 4 years or more after vaccination were 91.15% (95% CI: 67.61%-97.58%), 84.70% (95% CI: 43.71%-95.84%),56.23% (95% CI:-47.58%-87.02%), and 49.92% (95% CI:-83.74%-86.35%), respectively. Conclusion:The VE of aPV against pertussis in children aged 2 months to 6 years increases with the number of doses administered, and it is more effective in preventing hospitalization due to pertussis. The VE declines rapidly over time after the last dose. It is recommended to follow the new pertussis immunization program for timely and full vaccination.

Objective:To evaluate the epidemiological protective effect of a booster dose of acellular DTP vaccine (DTaP) against pertussis in 6-year-old children.Methods:A retrospective cohort study was conducted to compare the incidence of pertussis in 6-year-old children who received DTaP versus DT vaccine boosters in 2023 over a two-year period from May 2023 to May 2025. The protective effect of the fifth dose of DTaP against pertussis in 6-year-old children was evaluated.Results:A total of 960 participants were enrolled in this study, including 480 children in the experimental group who received the fifth dose of DTaP vaccine and 480 children in the control group who received the DT vaccine booster. Baseline characteristics were balanced between the two groups. There were six confirmed cases of pertussis in the experimental group, with a reported incidence rate of 1.25%. In the control group, 14 pertussis cases were reported, with a reported incidence rate of 2.92%. The protective effectiveness(VE) of the DTaP vaccine against pertussis was 57.14% (95% CI:-10.59%-83.39%). For 6-year-old children who completed the booster immunization, the incidence data of pertussis were collected from the 14 th day after vaccination (i.e., the study day 0). Based on the annual cumulative incidence rate, the VE of DTaP against pertussis at 6, 12, 18, and 24 months after vaccination was 100%, 63.80% (95% CI:-14.49%-88.55%), 64.59% (95% CI: 1.17%-87.31%), and 57.60% (95% CI:-10.80%-83.78%), respectively. In the DTaP group, the annual cumulative incidence rate of 12 to 24 months did not show a significant upward or downward trend ( Z=-0.995, P=0.320). Conclusion:Boosting 6-year-old children with the DTaP vaccine provides measurable protection against pertussis. The protective efficacy is significant in the early stage (0 to 6 months) after vaccination, and it still remains effective at 12 to 24 months.

The morbidity and mortality associated with diphtheria have been effectively managed through mass immunization strategies. Nevertheless, recent outbreaks of diphtheria have been reported in various regions of Africa and Asia. In addition to infections among children, there has been a notable increase in cases among middle-aged and elderly individuals, underscoring the necessity of continued vigilance in the control of diphtheria. This paper reviewed the epidemiology of diphtheria, the current application of vaccines, and immunization strategies, with the aim of providing evidence for the prevention and control of this disease.

Immunization represents the most effective strategy for the prevention and control of diseases. Nevertheless, some people may still get infected and contract the disease even after being fully vaccinated, which is known as a "breakthrough case." The presence of breakthrough cases shows that although vaccines significantly lower the rates of disease and death, they do not entirely eliminate the risk of illness.Addressing breakthrough cases, comprehending their epidemiological characteristics, and identifying the associated factors carry substantial public health implications for vaccine development, the optimization of vaccination strategies, and the implementation of intervention efforts. This review aims to provide a scientific reference for enhancing the prevention and control of vaccine-preventable diseases by summarizing the definitions, epidemiological characteristics, and relevant factors related to breakthrough infection cases across various diseases.