Objective: To investigate the trend in reported incidence of hepatitis B and to assess the effects of age, period, and birth cohort among people aged <30 years in Quzhou City, Zhejiang Province from 2005 to 2024. Methods: Reported cases of hepatitis B among people aged <30 years in Quzhou City from 2005 to 2024 were collected from the Infectious Disease Reporting Information System of Chinese Disease Prevention and Control Information System. The reported incidence was calculated. The average annual percent change (AAPC) was used to analyze the trend in reported incidence from 2005 to 2024. An age-period-cohort model was employed to analyze the effects of age, period, and birth cohort on the reported incidence of hepatitis B. Results: From 2005 to 2024, a total of 3 805 hepatitis B cases were reported among people aged <30 years in Quzhou City, with an average annual reported incidence of 31.61/100 000. The average annual reported incidence of hepatitis B was higher in males than in females (36.65/100 000 vs. 26.08/100 000, P<0.05). From 2005 to 2024, the reported incidence of hepatitis B among the entire people aged <30 years, as well as among males and females separately in Quzhou City, showed declining trends (AAPC=-9.887%, -10.415%, and -9.320%, respectively, all P<0.05). The age-period-cohort model analysis revealed that the incidence first decreased and then increased with age, declining from 4.21/105 in the age group of 0-<5 years to 2.07/105 in the age group of 10-<15 years, before rising to 22.49/105 in the age group of 25-<30 years. Using the 2010-2014 period as the reference, the risk of hepatitis B showed a decreasing trend over time. The RR value decreased from 1.842 (95%CI: 1.433-2.366) for 2005-2009 to 0.446 (95%CI: 0.294-0.675) for 2020-2024. Using the 2000-2004 birth cohort as the reference, the risk showed a decreasing trend with more recent birth years. The highest risk was observed in the 1980-1984 birth cohort, with an RR value of 4.731 (95%CI: 3.083-7.259). The age, period, and cohort effects on the reported incidence of hepatitis B among males and females were generally consistent with those observed in the entire population. Conclusions From 2005 to 2024, the reported incidence of hepatitis B among people aged <30 years in Quzhou City showed a declining trend, while exhibiting a pattern of first decreasing and then increasing with age. Furthermore, the risk of hepatitis B incidence demonstrated a decreasing trend over both time periods and birth cohorts.

Objective: To understand vaccination coverage and the influencing factors of varicella vaccine (VarV) among left-behind children in Quzhou, which based on protective motivation theory(PMT), so as to provide reference to consolidate VarV vaccination in the next step. Methods: From September to December in 2022, simple random sampling was used to select 628 left-behind children in six counties of Quzhou City. A questionnaire survey on their caregivers was conducted to collect data relating to sociological characteristics and PMT factors, and the influencing factors of VarV were tested by Logistic regression. Results: A total of 628 left-behind children participated in the study. The VarV rate was 69.59%, and 74.83% had received a second dose of VarV. The unvaccinated rate was 30.41%, and caregivers willingness to vaccinate children with VarV was only 10.99%. Logistic regression analysis showed that family relationships, annual household income, number of children in the family, extrinsic rewards and self-efficacy were the influencing factors of VarV among left-behind children ( OR =0.43-3.40， P <0.05). The external reward factor was positively correlated with the vaccination probability ( OR =1.14), and the self-efficacy factor was negatively correlated with the vaccination probability ( OR =0.95). Conclusion In the context of health education and school promotion, attention should be paid to factors relating to extrinsic rewards and self-efficacy as a means of increasing motivation to seek vaccine protection and improve the use of VarV.

Objective: To investigate the measles antibody level among residents in Quzhou City, Zhejiang Province in 2018, so as to provide the evidence for improving the measles control strategy. Methods: The permanent residents aged 0 to 59 years were randomly sampled from 10 townships ( streets ) in Kecheng District and Changshan County of Quzhou City. Residents' demographics and vaccination of measles-containing vaccine ( MCV ) were collected, and serum anti- measles IgG antibody was detected using enzyme-linked immunosorbent assay ( ELISA ). The positive rate, protective rate and geometric mean concentration (GMC) of anti-measles antibody were estimated. Results: A total of 606 residents were tested, with a male to female ratio of 0.83∶1. The subjects had a median age ( interquartile range ) of 17.36 ( 29.07 ) years, and 399 residents ( 65.84% ) had a vaccination history of MCV. The positive rate, protective rate and GMC of anti-measles IgG antibody were 94.88%, 48.68%, and 784.51 ( 95%CI: 731.14-841.40) mIU/mL, respectively. The positive rate of anti-measles IgG antibody was higher in men than in women ( 97.08% vs. 93.07%, χ2=4.968, P=0.026 ), and the protection rate was lower in men than in women ( 44.16% vs. 52.41%, χ2=4.089, P=0.043 ). The protective rate and GMC of anti-measles IgG antibody showed a“U”-shaped distribution with age, and a low protective rate was seen in residents aged 10 to 39 years ( 23.53% to 46.67% ), which the GMC of anti-measles IgG antibody that did not reach the protective level. A total of 233 residents at age of 15 years and below had with a history of two-dose MCV vaccination, and the positive rate ( χ2trend=7.260, P=0.007 ), protective rate ( χ2trend=12.756, P<0.001 ) and GMC ( rs=-0.289, P<0.001 ) of anti-measles IgG antibody presented a tendency towards a reduction with time <1 to 11 years after vaccination of the last dose of MCV. Conclusions A high positive rate of anti-measles antibody was detected among residents in Quzhou City in 2018; however, the protection rate of anti-measles antibody was low among residents at ages of 10 to 39 years. The coverage of MCV vaccination is recommended to be improved among residents at ages of 10 to 39 years in Quzhou City.