Assessing vaccination coverage, timeliness, and its temporal variations among children in a rural area in China

Dynamics of measles immunity from birth and following vaccination

Measles remains a major threat to human health despite widespread vaccination. While we know that maternal antibodies can impair vaccine-induced immunity, the relative contributions of pre-existing immunity levels, maternal and infant characteristics on vaccine responses remain unclear, hampering evidence-based vaccination policy development. Here we combine serological data from 1,505 individuals (aged 0-12 years) in a mother-infant cohort and in a child cohort with empirical models to reconstruct antibody trajectories from birth. We show that while highly heterogeneous across a population, measles antibody evolution is strongly predictive from birth at the individual level, including following vaccination. Further, we find that caesarean section births were linked with 2.56 (95% confidence interval: 1.06-6.37) increased odds of primary vaccine failure, highlighting the long-term immunological consequences of birth route. Finally, we use our new understanding of antibody evolution to critically assess the population-level consequences of different vaccination schedules, the results of which will allow country-level evaluations of vaccine policy.

Transplacental transfer efficiency of maternal antibodies against influenza A(H1N1)pdm09 virus and dynamics of naturally acquired antibodies in Chinese children: a longitudinal, paired mother-neonate cohort study

BACKGROUND

The 2009 pandemic H1N1 influenza A virus (A(H1N1)pdm09 virus) evolves rapidly and has continued to cause severe infections in children since its emergence in 2009. We aimed to characterise the kinetics of maternally and naturally acquired antibodies against historical A(H1N1)pdm09 strains and to assess the extent to which the response to heterologous strains following infection or vaccination affects observed A(H1N1)pdm09 strain-specific antibody titres in a Chinese paediatric population.

METHODS

In this retrospective study, we used residual serum samples from 528 mother-neonate pairs from a non-interventional, longitudinal cohort study in southern China conducted from Sept 20, 2013, to Aug 24, 2018, from six local hospitals in Anhua County, Hunan Province, China. Mother-neonate pairs were eligible for inclusion if the neonates were born after Sept 20, 2013, and their mothers had resided in the study sites for at least 3 months. We tested samples with a haemagglutination inhibition (HAI) assay to measure antibody levels against three historical A(H1N1)pdm09 strains that were antigenically similar to the strains that circulated during the 2009 pandemic (A/Hunan-Kaifu/SWL4204/2009 [SWL4204/09 strain], A/Hunan-Daxiang/SWL1277/2016 [SWL1277/16 strain], and A/Hunan-Yanfeng/SWL185/2018 [SWL185/18 strain]). We also determined the seroprevalence, geometric mean titres (GMTs), transfer ratio of maternal antibodies, and the dynamics of maternally and naturally acquired antibodies in children, from birth to 3 years of age.

FINDINGS

1066 mother-neonate pairs were enrolled in the original cohort between Sept 20, 2013, and Oct 14, 2015. Of these, 528 pairs (523 mothers, 528 neonates) were selected for the present study. The median age of the mothers was 25 years (IQR 23 to 29). 291 (55%) of 528 children were boys and 237 (45%) were girls, and most children (452 [86%]) were breastfed before the age of 6 months. The GMTs and the seroprevalence for the SWL4204/09 strain were higher than those for the SWL1277/16 and SWL185/18 strains among mothers (GMTs: 10·4 [95% CI 9·8 to 11·1] vs 9·3 [8·7 to 9·8] vs 8·0 [7·5 to 8·4], p<0·0001; seroprevalence: 11·1% [95% CI 8·5 to 14·1] vs 6·9% [4·9 to 9·4] vs 4·6% [3·0 to 6·8], p=0·0003) and among neonates (GMTs: 10·7 [10·0 to 11·5] vs 9·4 [8·8 to 10·0] vs 8·1 [7·6 to 8·6], p<0·0001; seroprevalence: 13·4% [10·7 to 16·7] vs 8·7% [6·5 to 11·5] vs 6·1% [4·2 to 8·5], p=0·0002). Regardless of the A(H1N1)pdm09-specific strain, maternal antibodies could be transferred efficiently via the placenta (mean transfer ratios: 1·10 for SWL4204/09 vs 1·09 for SWL1277/16 vs 1·06 for SWL185/18; p=0·93). The A(H1N1)pdm09 strain-specific antibodies waned below the protective threshold of 1:40 within 2 months after birth. After maternal antibody waning, there were periodic increases and decreases in HAI antibody titres against three A(H1N1)pdm09 strains, and such increases were all significantly associated with a higher immune response to heterologous strains. Vaccination against the SWL4204/09 strain was associated with a poor response to the SWL185/18 strain (β-0·20, 95% CI -0·28 to -0·13; p<0·0001).

INTERPRETATION

Our findings suggest low pre-existing immunity against influenza A(H1N1)pdm09 virus among unvaccinated Chinese adult female and paediatric populations. This evidence, together with the rapid decay of maternal antibodies and the observed cross-reactivity among different A(H1N1)pdm09 strains, highlights the importance of accelerating maternal and paediatric influenza vaccination in China.

FUNDING

The Key Program of the National Natural Science Foundation of China.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

Cost-effectiveness of seasonal influenza vaccination of children in China: a modeling analysis

BACKGROUND

China has a high burden of influenza-associated illness among children. We aimed to evaluate the cost-effectiveness of introducing government-funded influenza vaccination to children in China (fully-funded policy) compared with the status quo (self-paid policy).

METHODS

A decision tree model was developed to calculate the economic and health outcomes, from a societal perspective, using national- and provincial-level data. The incremental cost-effectiveness ratio (ICER) [incremental costs per quality-adjusted life year (QALY) gained] was used to compare the fully-funded policy with the self-paid policy under the willingness-to-pay threshold equivalent to national and provincial GDP per capita. Sensitivity analyses were performed and various scenarios were explored based on real-world conditions, including incorporating indirect effect into the analysis.

RESULTS

Compared to the self-paid policy, implementation of a fully-funded policy could prevent 1,444,768 [95% uncertainty range (UR): 1,203,446-1,719,761] symptomatic cases, 92,110 (95% UR: 66,953-122,226) influenza-related hospitalizations, and 6494 (95% UR: 4590-8962) influenza-related death per season. The fully-funded policy was cost-effective nationally (7964 USD per QALY gained) and provincially for 13 of 31 provincial-level administrative divisions (PLADs). The probability of a funded vaccination policy being cost-effective was 56.5% nationally, and the probability in 9 of 31 PLADs was above 75%. The result was most sensitive to the symptomatic influenza rate among children under 5 years [ICER ranging from - 25,612 (cost-saving) to 14,532 USD per QALY gained]. The ICER of the fully-funded policy was substantially lower (becoming cost-saving) if the indirect effects of vaccination were considered.

CONCLUSIONS

Introducing a government-funded influenza policy for children is cost-effective in China nationally and in many PLADs. PLADs with high symptomatic influenza rate and influenza-associated mortality would benefit the most from a government-funded influenza vaccination program.

Vaccination coverage determinants in low uptake areas of China: a qualitative study of provider perspectives in Sichuan, Guangdong, and Henan Provinces

China’s immunization programme is relatively strong, with latest WHO-UNICEF monitoring rates for 2019 showing national vaccination coverage over 90%. However, vaccination coverage is heterogeneous, varying across geographic regions, rural–urban communities, and sub-populations. We conducted a qualitative study from a critical realist perspective, analyzing semi-structured interviews with 26 vaccination providers in three provinces, selected to represent regional socioeconomic disparities across Eastern, Central, and Western China. We analyzed data thematically, using deductive and inductive coding. Providers reported vaccination coverage in their areas had increased significantly, but remained lower among migrant and left-behind children. Main coverage determinants were child-related (i.e. gender, number, health status), caregiver-related (i.e. socioeconomic status, role, education level, ethnicity), institution-related (i.e. vaccinator numbers, information system, appointment process), and system-related (i.e. vaccine supply, intersectoral cooperation, vaccine ‘hesitancy’). Potentially effective measures to promote vaccination coverage included using routine maternal and child health-care visits for catch-up vaccination, providing additional health education, conducting follow-up family visits by village doctors, and requiring vaccination verification at school enrollment. This is the first qualitative study to examine potential determinants of low vaccination coverage in these areas of China. Findings can inform policies to strengthen the role of schools, develop the national immunization information system, and promote appointment apps. More consideration is needed to improve service quality and eliminating inequities, such as strengthening health education and service provision for migrant and left-behind children.

Delays in routine childhood vaccinations and their relationship with parental vaccine hesitancy: a cross-sectional study in Wuxi, China

OBJECTIVES

This study aimed to examine childhood vaccination delay, explore the association between vaccination delay and parental vaccine hesitancy, and assess childhood vaccination delays during the coronavirus disease (COVID)-19 pandemic in China.

METHODS

This cross-sectional survey was conducted in Wuxi City. Participants were recruited from local vaccination clinics. Questionnaires were used to collect information about socio-demographics, vaccine hesitancy, and immunization clinic evaluations. Vaccination records were obtained from the Jiangsu Information Management System of Vaccination Cases.

RESULTS

Overall, 2728 participants were included. The coverage for seven category A vaccines (Expanded Program on Immunization (EPI)) was more than 95% at 24 months. The proportion of children vaccinated in a timely manner was the highest for the first dose of the hepatitis B vaccine (91.6%) and the lowest for the Bacillus-Calmette-Guerin vaccine (44.6%). More than 50% of the planned vaccinations were delayed in February and March 2020. The Vaccine Hesitancy Scale scores were not associated with vaccination delay (P = 0.842). Children's vaccination delays were negatively associated with parents who reported convenient access to clinics and satisfaction with immunization services (P = 0.020, P = 0.045).

CONCLUSIONS

EPI is highly successful in China. Despite vaccination delays due to the COVID-19 pandemic, coverage was recovered after lockdown restrictions were eased.

Cost-effectiveness analysis of domestic 13-valent pneumococcal conjugate vaccine for children under 5 years of age in mainland China

Background: The first Chinese domestic 13-valent pneumococcal conjugate vaccine (WoAnxin®, PCV-13) is available for children aged 2 months to 5 years and is more economical than import vaccine with equal safety and immunogenicity. However, the cost-effectiveness of this new PCV-13 for children <5 years in mainland China is not clear. Methods: In the present study, we developed a Markov model under societal perspective to evaluate the incremental cost-effectiveness ratios (ICERs) of five birth cohorts of 100,000 Chinese infants across four alternative vaccination programs:1) no vaccination; 2) vaccinate 4 doses of new PCV-13 for children aged 2 to 6 months; 3) vaccinate 3 doses of new PCV-13 for children aged 7 to 11 months; 4) vaccinate 2 doses of new PCV-13 for children aged 12 to 23 months; 5) vaccinate 1 dose of new PCV-13 for children aged 2 to 5 years. We conducted one-way and probability sensitivity analysis to determine the uncertainty of the model findings. Results: We found that with awillingness-to-pay (WTP) threshold of three-times Chinese per-capita gross domestic product (GDP) all vaccination programs were cost-effective compared to no vaccination and children aged 2 to 5 years received 1 dose of new PCV-13 would incur the lowest additional cost of US$2417 per quality-adjusted-life-years (QALYs) compare with other vaccination programs ($15394/QALYs for 4 doses program, $9292/QALYs for 3 doses program, $4445/QALYs for 2 doses program). Conclusions: According to our results, China should give priority to incorporating new PCV-13 into its national immunization program.