Two-dose varicella vaccine effectiveness in China: a meta-analysis and evidence quality assessment

Trends and Age-Period-Cohort Effect on Incidence of Varicella Under Age 35 - China, 2005-2021

What is already known about this topic?

Varicella is an acute respiratory infectious disease primarily affecting children. However, recent studies have indicated an increasing susceptibility to varicella among older age groups.

What is added by this report?

The findings demonstrate a significant rise in the incidence rate among individuals aged 15-19. Males under 20 years old were found to have a higher risk compared to females, whereas males had a lower risk compared to females aged 20-35 years.

What are the implications for public health practice?

This study is the first comparative analysis using varicella data reported between 2005 and 2021 to examine the contributions of age, period, and birth cohort to varicella incidence in China. This study aims to provide a comprehensive analysis of the epidemiological characteristics of varicella in China and identify high-risk groups. The results of this study will contribute valuable information for the development of varicella prevention policies.

Immunogenicity and safety of a live-attenuated varicella vaccine in a healthy population aged 13 years and older: A randomized, double-blind, controlled study

OBJECTIVES

Vaccines for prevention against varicella are important for adolescents and adults, who have an increased risk of severe varicella. This study aimed to evaluate the immunogenicity and safety of a two-dose immunization schedule of a live-attenuated varicella vaccine (VarV) manufactured by Sinovac (Dalian) in healthy adolescents and adults.

METHODS

A randomized, double-blind, controlled clinical trial was conducted in healthy population aged ≥ 13 years old in China. Participants in block 1 were randomly assigned (1:1) to receive two doses of either the test vaccine or an active control vaccine, administered 4, 6 or 8 weeks apart. Participants in block 2 were randomly assigned (2:1) to receive two doses of test vaccine or placebo, administered 10 weeks apart. The primary immunogenicity endpoint was the seroconversion rates and GMTs of varicella zoster virus (VZV) antibodies measured by fluorescent-antibody-to-membrane-antigen (FAMA) 4 weeks post-immunization. The primary safety endpoint was the incidence of adverse reactions within 4 weeks after each dose.

RESULTS

A total of 2398 participants were enrolled. The seroconversion rates of VZV antibodies were 79.55 % in the test group and 76.41 % in the active control group respectively 4 weeks after two doses of pooled schedule, with the difference of 3.14 % (95 %CI: -0.69 %, 6.97 %). The GMTs were 1:162.07 and 1:160.04 respectively, with the ratio of 1.013 (95 %CI: 0.910, 1.127). Both the seroconversion rates and GMTs reached the prespecified non-inferiority criteria. Two-dose schedule with an interval of 10 weeks could also induce high immune responses, with a seroconversion rate of 83.22 % and a GMT of 1:160.38 in the test group. Safety profiles were similar among the test group, active control group and placebo group.

CONCLUSION

VarV, manufactured by Sinovac (Dalian), demonstrated higher immune response and better flexibility in the immunization schedule among heathy population aged 13 years and older, without increased safety risk.

Epidemiological Characteristics of Varicella Outbreaks - China, 2006-2022

Introduction

Varicella outbreaks significantly disrupt schools and other child-centered institutions. This study aimed to identify patterns and epidemiological features of varicella outbreaks in China from 2006 to 2022.

Methods

Data were extracted from outbreak reports submitted to the Public Health Emergency Reporting Management Information System within the specified timeframe. Analytical methods included Spearman correlation tests and the Mann-Kendall trend tests, conducted using R software to analyze and summarize reported data. Additionally, statistical analyses of trends and epidemiological characteristics were performed using SPSS software.

Results

Between 2006 and 2022, a total of 11,990 varicella outbreaks were reported in China, resulting in 354,082 cases. The attack rates showed a decreasing trend over the years (Z=-4.49, P<0.05). These outbreaks occurred in two peaks annually. The eastern region accounted for the highest number of outbreaks (31.53%), followed by the southwestern (24.22%) and southern (17.93%) regions. Varicella outbreaks were most common in elementary schools. Most of the outbreaks (60.43%) were classified as Grade IV (general) severity, with 86.41% of the outbreaks having 10-49 cases. The median and inter-quartile ranges (IQR) of the duration of outbreaks, response time, and case counts were 21 (10, 39) days, 4 (0, 12) days, and 23 (16, 35) cases, respectively. These variables showed a positive correlation (P<0.001).

Conclusions

Varicella outbreaks exhibited fluctuating trends, initially decreasing until 2012, followed by an increase, reaching the highest peak in 2018-2019. Continual monitoring of varicella epidemiology is necessary to assess the burden of the disease and formulate evidence-based strategies and policies for its prevention and control.

Factors associated with recommendation behaviors of four non-National Immunization Program vaccines: a cross-sectional survey among public health workers in China

BACKGROUND

Immunization is a crucial preventive measure to safeguard children under five years old against a range of diseases. In China, the coverage rate of non-National Immunization Program (non-NIP) vaccines can be improved by leveraging the recommendation from public health workers. Hence, understanding the influencing factors of recommendation behaviors assume paramount importance. This study aims to investigate influencing factors of public health workers' recommendation behaviors towards non-NIP vaccines, with a particular emphasis on financial incentives.

METHODS

A cross-sectional survey was conducted using a multi-stage sampling method in 2019 from August to October. 627 public health workers were recruited from 148 community healthcare centers in ten provincial-level administrative divisions in China. An anonymous questionnaire was used to collect demographic information, attitudes towards vaccination, and recommendation behaviors towards non-NIP vaccines, including Haemophilus influenzae type b (Hib) vaccine, pneumococcal conjugate vaccine, varicella vaccine, and rotavirus vaccine. Descriptive analysis and multivariate logistic regression analysis were adopted in this study.

RESULTS

Of the 610 public health workers with complete survey data, 53.8%, 57.4%, 84.1%, and 54.1% often recommended Hib vaccine, pneumococcal pneumonia vaccine (PCV), varicella vaccine, and rotavirus vaccine, respectively. Logistic regression revealed that gender (Hib vaccine: OR = 0.4, 95% CI: 0.2-0.8; PCV: OR = 0.4, 95% CI: 0.2-0.8; rotavirus vaccine: OR = 0.3, 95% CI: 0.2-0.6), financial incentives for non-NIP vaccination (Hib vaccine: OR = 1.9, 95% CI: 1.1-3.6; PCV: OR = 2.1, 95% CI: 1.1-3.9; rotavirus vaccine: OR = 2.0, 95% CI: 1.1-3.8) and perception of vaccine safety (Hib vaccine: OR = 2.7, 95% CI: 1.1-7.0; PCV: OR = 3.2, 95% CI: 1.2-8.0; rotavirus vaccine: OR = 3.0, 95% CI: 1.2-7.7) were associated with public health workers' recommendation towards Hib vaccine, PCV and rotavirus vaccine.

CONCLUSIONS

The findings highlighted public health workers' recommendation behaviors of non-NIP vaccines in China and revealed strong association between vaccine recommendation and financial incentives. This highlights the importance of financial incentives in public health workers' recommendation toward non-NIP vaccines in China. Proper incentives are recommended for public health workers to encourage effective health promotion in immunization practices.

The epidemiology of varicella and effectiveness of varicella vaccine in Ganyu, China: a long-term community surveillance study

BACKGROUND

The real-world data of long-term protection under moderate vaccination coverage is limited. This study aimed to evaluate varicella epidemiology and the long-term effectiveness under moderate coverage levels in Ganyu District, Lianyungang City, Jiangsu Province.

METHODS

This was a population-based, retrospective birth cohort study based on the immunization information system (IIS) and the National Notifiable Disease Surveillance System (NNDSS) in Ganyu District. Varicella cases reported from 2009 to 2020 were included to describe the epidemiology of varicella, and eleven-year consecutive birth cohorts (2008-2018) were included to estimate the vaccine effectiveness (VE) of varicella by Cox regression analysis.

RESULTS

A total of 155,232 native children and 3,251 varicella cases were included. The vaccination coverage was moderate with 37.1%, correspondingly, the annual incidence of varicella infection increased 4.4-fold from 2009 to 2020. A shift of the varicella cases to older age groups was observed, with the peak proportion of cases shifting from 5-6 year-old to 7-8 year-old. The adjusted effectiveness of one dose of vaccine waned over time, and the adjusted VE decreased from 72.9% to 41.8% in the one-dose group.

CONCLUSIONS

The insufficient vaccination coverage (37.1%) may have contributed in part to the rising annual incidence of varicella infection, and a shift of varicella cases to older age groups occurred. The effectiveness of one dose of varicella vaccine was moderate and waned over time. It is urgent to increase varicella vaccine coverage to 80% to reduce the incidence of varicella and prevent any potential shift in the age at infection in China.

The incidence of herpes zoster in China: A meta-analysis and evidence quality assessment

This review aimed to estimate the disease burden of herpes zoster (HZ) in China and explore the application of the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach in studies of disease burden. We searched for the literature of observational studies analyzing HZ incidence in populations of all ages in China. Meta-analysis models were constructed to calculate the pooled incidence of HZ and pooled risks of postherpetic neuralgia (PHN), HZ recurrence, and hospitalization. Subgroup analysis was performed according to gender, age, and quality assessment score. The quality of evidence for incidence was rated using the GRADE system. Twelve studies with a total of 25,928,408 participants were included in this review. The pooled incidence for all ages was 4.28/1000 person years (95% CI 1.22-7.35). It increased with the increasing in age especially for individuals aged ≥60 y, which was 11.69/1000 person years (95% CI 6.56-16.81). The pooled risks of PHN, recurrence, and hospitalization were 12.6% (95% CI 10.1-15.1), 9.7% (95% CI 3.2-16.2), and 6.0/100,000 population (95% CI 2.3-14.2), respectively. The quality of the evidence assessment of the pooled incidence by the GRADE for all ages was 'low'; however, it was 'moderate' for the ≥60 yold subgroup. HZ is a serious public health problem in China and is more significant in individuals older than 60 y. Therefore, an immunization strategy for the zoster vaccine should be considered. The evidence quality assessment by the GRADE approach indicated that we had more confidence in the estimation of aged population.

Using Baidu Index Data to Improve Chickenpox Surveillance in Yunnan, China: Infodemiology Study

BACKGROUND

Chickenpox is an old but easily neglected infectious disease. Although chickenpox is preventable by vaccines, vaccine breakthroughs often occur, and the chickenpox epidemic is on the rise. Chickenpox is not included in the list of regulated communicable diseases that must be reported and controlled by public and health departments; therefore, it is crucial to rapidly identify and report varicella outbreaks during the early stages. The Baidu index (BDI) can supplement the traditional surveillance system for infectious diseases, such as brucellosis and dengue, in China. The number of reported chickenpox cases and internet search data also showed a similar trend. BDI can be a useful tool to display the outbreak of infectious diseases.

OBJECTIVE

This study aimed to develop an efficient disease surveillance method that uses BDI to assist in traditional surveillance.

METHODS

Chickenpox incidence data (weekly from January 2017 to June 2021) reported by the Yunnan Province Center for Disease Control and Prevention were obtained to evaluate the relationship between the incidence of chickenpox and BDI. We applied a support vector machine regression (SVR) model and a multiple regression prediction model with BDI to predict the incidence of chickenpox. In addition, we used the SVR model to predict the number of chickenpox cases from June 2021 to the first week of April 2022.

RESULTS

The analysis showed that there was a close correlation between the weekly number of newly diagnosed cases and the BDI. In the search terms we collected, the highest Spearman correlation coefficient was 0.747. Most BDI search terms, such as "chickenpox," "chickenpox treatment," "treatment of chickenpox," "chickenpox symptoms," and "chickenpox virus," trend consistently. Some BDI search terms, such as "chickenpox pictures," "symptoms of chickenpox," "chickenpox vaccine," and "is chickenpox vaccine necessary," appeared earlier than the trend of "chickenpox virus." The 2 models were compared, the SVR model performed better in all the applied measurements: fitting effect, R²=0.9108, root mean square error (RMSE)=96.2995, and mean absolute error (MAE)=73.3988; and prediction effect, R²=0.548, RMSE=189.1807, and MAE=147.5412. In addition, we applied the SVR model to predict the number of reported cases weekly in Yunnan from June 2021 to April 2022 using the same period of the BDI. The results showed that the fluctuation of the time series from July 2021 to April 2022 was similar to that of the last year and a half with no change in the level of prevention and control.

CONCLUSIONS

These findings indicated that the BDI in Yunnan Province can predict the incidence of chickenpox in the same period. Thus, the BDI is a useful tool for monitoring the chickenpox epidemic and for complementing traditional monitoring systems.

Effects of meteorological factors on the incidence of varicella in Lu'an, Eastern China, 2015-2020

Varicella (chickenpox) is a serious public health problem in China, with the most reported cases among childhood vaccine-preventable infectious diseases, and its reported incidence has increased over 20-fold since 2005. Few previous studies have explored the association of multiple meteorological factors with varicella and considered the potential confounding effects of air pollutants. It is the first study to investigate and analyze the effects of multiple meteorological factors on varicella incidence, controlling for the confounding effects of various air pollutants. Daily meteorological and air pollution data and varicella cases were collected from January 1, 2015, to December 31, 2020, in Lu'an, Eastern China. A combination of the quasi-Poisson generalized additive model (GAM) and distributed lag nonlinear model (DLNM) was used to evaluate the meteorological factor-lag-varicella relationship, and the risk of varicella in extreme meteorological conditions. The maximum single-day lag effects of varicella were 1.288 (95%CI, 1.201-1.381, lag 16 day), 1.475 (95%CI, 1.152-1.889, lag 0 day), 1.307 (95%CI, 1.196-1.427, lag 16 day), 1.271 (95%CI, 0.981-1.647, lag 4 day), and 1.266 (95%CI, 1.162-1.378, lag 21 day), when mean temperature, diurnal temperature range (DTR), mean air pressure, wind speed, and sunshine hours were -5.8°C, 13.5°C, 1035.5 hPa, 6 m/s, and 0 h, respectively. At the maximum lag period, the overall effects of mean temperature and pressure on varicella showed W-shaped curves, peaked at 17.5°C (RR=2.085, 95%CI: 1.480-2.937) and 1035.5 hPa (RR=5.481, 95%CI: 1.813-16.577), while DTR showed an M-shaped curve and peaked at 4.4°C (RR=6.131, 95%CI: 1.120-33.570). Sunshine hours were positively correlated with varicella cases at the lag of 0-8 days and 0-9 days when sunshine duration exceeded 10 h. Furthermore, the lag effects of extreme meteorological factors on varicella cases were statistically significant, except for the extremely high wind speed. We found that mean temperature, mean air pressure, DTR, and sunshine hours had significant nonlinear effects on varicella incidence, which may be important predictors of varicella early warning.

National and provincial burden of varicella disease and cost-effectiveness of childhood varicella vaccination in China from 2019 to 2049: a modelling analysis

Background

In China, varicella is the third most frequently reported vaccine-preventable infectious disease after tuberculosis and influenza, and imposes a heavy burden on families and society. To inform future immunization policy, we investigated disease burden of varicella in China and explored cost-effectiveness of different varicella vaccination strategies at national and provincial levels.

Methods

A dynamic transmission model was developed to assess disease burden of varicella and the impact of varicella vaccination in China. A cost-effectiveness analysis of three alternative vaccination strategies in China's National Immunization Program (NIP) compared with no vaccination was conducted. Scenario analyses and sensitivity analyses were performed to check the robustness of the results.

Findings

It was estimated that 3.35 million new varicella cases occurred in 2019, more than three times of 982 thousand cases officially reported from National Notifiable Infectious Disease Surveillance System (NNIDSS). The under-reported rate was approximately 71%. The economic analysis revealed that from the societal perspective, the incremental cost-effectiveness ratio (ICER) for one dose of varicella vaccination in NIP was US$ 2357 per QALY at the national level and it was cost-effective in 22 of 31 provinces. The ICER for one dose varicella vaccination plus a mass catch-up for unvaccinated children aged 2-11 years old would be US$ -5260 per QALY, cost-saving at the national level. The one dose plus mass catch-up NIP strategy was also cost-saving in 24 of the 31 provinces.

Interpretation

Varicella incident cases were substantially under-reported in China. Varicella vaccination in the NIP could significantly contribute to reducing the burden of varicella disease. From the societal perspective, including varicella vaccination into China's NIP was highly cost-effective at the national level and in most provinces.

Funding

Bill & Melinda Gates Foundation.

Long-term vaccine efficacy of a 2-dose varicella vaccine in China from 2011 to 2021: A retrospective observational study

Objective

A 2-dose varicella vaccine immunization strategy has been implemented in many cities in China, but there is few evidence on a long-term evaluation of the efficacy of the 2-dose varicella vaccine from China. This study aims to assess the long-term vaccine efficacy of the two doses varicella vaccine and analysis of its influencing factors.

Methods

A retrospective study was carried out in 837,144 children born between 2011 and 2017 in Ningbo, Easten China. The logistic regression was performed to estimate varicella vaccine effectiveness (VE).

Results

The overall VE of 2 doses of varicella vaccine compared without the vaccine was 90.31% (89.24-91.26%), and the overall incremental VE of 2 doses of varicella vaccine compared to the 1-dose was 64.71% (59.92-68.93%). Moreover, the varicella vaccination age of the second dose and the interval between 2 doses were both associated with VE. The VE compared to that without the vaccine in children vaccinated at <4 years old was 91.22% (95%CI: 90.16-92.17%) which was higher than in children vaccinated at ≥4 years old (VE: 86.79%; 95%CI: 84.52-88.73). And the effectiveness of the vaccine was 93.60% (95%CI: 92.19-94.75%) in children with the interval of the 2 doses ≤ 24 months significantly higher than in children with the interval of ≥36 months (VE: 85.62%, 95%CI: 82.89-87.91%).

Conclusions

This study provides evidence for long-term VE of the 2-dose varicella vaccine and the better age for 2-dose vaccination and the interval between 2 doses of the vaccine in China.

Epidemiological Characteristics of Varicella under Different Immunisation Strategies in Suzhou Prefecture, Jiangsu Province

Background: The varicella vaccine is excluded from the Chinese national immunisation programme but is included in the local expanded programme on immunisation (EPI) in the Suzhou Prefecture. This study investigated the epidemiological characteristics of the varicella cases during the implementation of different immunisation strategies in the Suzhou Prefecture, Jiangsu Province. Methods: In this study, we used descriptive statistics. Information on reported instances from 2012 to 2021 was first retrieved. Data on varicella cases were collected from the China Information System for Disease Control and Prevention (CISDCP). Similarly, information on vaccinated children was obtained from the Jiangsu Province Vaccination Integrated Service Management Information System (JPVISMIS). The census data in this study was procured from the Suzhou Bureau of Statistics. Results: From 2012 to 2021, a total of 118,031 cases of varicella were reported in Suzhou, and the average annual reported incidence was 91.35 per 100,000. The average yearly incidence after implementing the two-dose varicella vaccination decreased by 41.57% compared with the implementation of one dose. This study demonstrates two annual incidence peaks, a small peak between April and July and a prominent peak between October and January. It is also possible that this seasonal distribution is related to the geography of Suzhou. The average annual reported incidence between districts with a statistically significant difference (χ2 = 98.077, p < 0.05). The one-dose varicella vaccination coverage gradually increased from 55.34% in 2012 to 89.06% in 2021 and the two-dose varicella vaccination coverage gradually increased from 0.27% in 2012 to 82.17% in 2021. Conclusions: Administering the varicella vaccine in the local EPI has significantly decreased the incidence rate and the total number of cases. A two-dose vaccination schedule is still the best vaccination strategy for varicella vaccine effectiveness.