An Evaluation of Voluntary Varicella Vaccination Coverage in Zhejiang Province, East China

Determinants of parental demand of human papillomavirus vaccination for adolescent daughters in China: Contingent valuation survey

BACKGROUND

Several types of human papillomavirus (HPV) vaccines have been approved for use in adolescent girls in China. These vaccines are regulated as non-National Immunisation Program vaccines and are optional and generally fully self-paid by vaccinees.

OBJECTIVE

To assess parents' demand for HPV vaccination by eliciting their willingness-to-pay for their adolescent daughters to be vaccinated against HPV and to examine the determinants of demand for HPV vaccination in China.

METHODS

A contingent valuation survey was conducted across three cities in Shandong Province in eastern China. We selected 11 junior middle schools with different socioeconomic features and randomly selected 6 classes in each school, and questionnaires were distributed to all girls aged 12-16 in the 66 classes for their parents to complete. A payment card approach was used to elicit parental willingness-to-pay for HPV vaccination for their daughters. We also collected a wide array of socioeconomic and psychological variables and interval regressions were applied to examine the determinants of parental willingness-to-pay.

RESULTS

A total of 1074 eligible parents who completed valid questions were included in analyses. Over 85% of parents believed HPV vaccines were, in general, necessary and beneficiary. However, only around 10% believed that their daughters would be infected by HPV. About 8% of parents would not accept HPV vaccine even if the vaccine were free mainly due to concerns about the potential side effects and vaccine safety and quality issues, and 27.37% would only accept the vaccine if it were free. The median willingness-to-pay was 300 CNY (42 USD). Several factors were positively correlated with higher willingness-to-pay: income, urban residence (relative to rural residence), mothers (relative to fathers), parents' beliefs about vaccine benefits, whether they should make decisions for their daughters, and whether their daughters would be susceptible to HPV. Though education-level was not significantly correlated with willingness-to-pay in the main regressions, a subgroup analysis revealed interesting dynamics in the relation between education and willingness-to-pay across different income-levels.

CONCLUSIONS

There is a large gap between parents' willingness-to-pay and the market price of HPV vaccine for girls in China. Parents generally believed the HPV vaccines were beneficial and necessary but when asked for their daughters, most parents did not believe their daughters would be infected by HPV despite the high prevalence in China. Future focus should be on ensuring the provision of accurate health information about HPV prevalence, vaccine quality, and safety to promote vaccine uptake, and promotional efforts tailored to different income groups might yield better effects. Government involvement in negotiating more widely acceptable and affordable prices or subsidising may be necessary for protecting high-risk population groups.

Impact of Varicella Immunization and Public Health and Social Measures on Varicella Incidence: Insights from Surveillance Data in Shanghai, 2013-2022

To evaluate the impact of a two-dose VarV program on varicella incidence among the whole population, considering the influence of public health and social measures (PHSMs), we extracted surveillance data on varicella cases during 2013-2022 in Minhang, Shanghai. Then, we estimated the incidence trend of varicella through interrupted time-series analyses and quantified the impact of the immunization program and PHSMs using Serfling regression. We also explored the associations between PHSMs and varicella cases. The implementation of the two-dose VarV strategy was followed by a significant decrease in varicella incidence (-1.84% per month). After one year of the program, varicella incidence was estimated at a 45.25% reduction, which was higher in children (59.12% and 54.09%) than in adults (19.49%). The decrease attributed to PHSMs was 31.26% during 2020-2022, and school closing was identified as the most relevant PHSM (b = -8.03 cases, r = -0.67 with a 1-week lag). These findings indicate that the two-dose immunization program has more effectively reduced the varicella incidence compared with the one-dose vaccine, and interventions like school closings are also encouraged to serve as supplementary measures to prevent varicella epidemics.

Vaccination coverage estimates and utilization patterns of inactivated enterovirus 71 vaccine post vaccine introduction in Ningbo, China

Background

In China, enterovirus 71 (EV71) is the major etiological agents of hand foot mouth disease that poses severe risks to children’s health. Since 2015, three inactivated EV71 vaccines have been approved for use. Previous studies indicated the high willingness of EV71 vaccination in eastern China. However, few studies have assessed coverage and utilization patterns of EV71 vaccine in China.

Methods

Children born during 2012–2018 were sampled and their records were abstracted from Ningbo childhood immunization information management system. Descriptive statistics characterized the study population and assessed coverage and timeliness for EV71 vaccination. Simultaneous administration patterns as well as type of EV71 vaccine used were also evaluated. Bivariate and multivariable analysis was used to examine the relationship of socio-demographic characteristics with vaccination coverage and timeliness.

Results

Of 716,178 children living in Ningbo. One hundred seventy-two thousand two hundred thirty-six received EV71 vaccine with a coverage rate of 24.05% and only 8.61% received vaccination timely. 21.97% of children received the complete two dose EV71 series but only 6.49% completed timely. Vaccination coverage and timeliness increased significantly from 2012 birth cohort to 2018 birth cohort. Relatively higher coverage and timeliness were observed in resident children, Inner districts, high socioeconomic areas and large-scaled immunization clinics. Of 329,569 doses of EV71 vaccine, only 5853(1.78%) doses were administered at the same day as other vaccines.

Conclusions

There is a need for increasing EV71 vaccination coverage and timeliness as well as eliminating disparities among different populations. Our study highlights the importance of simultaneous administration to increasing coverage and timeliness of EV71 vaccination.

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

BACKGROUND

The objectives of this review were to evaluate the vaccine effectiveness (VE) of the two-dose varicella vaccine for healthy children in China and explore the application of the approach of Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) in observational studies on VE.

METHODS

We searched for observational studies on two-dose varicella VE for children in China aged 1-12 years that were published from 1997 to 2019, and assessed the quality of each study using the Newcastle Ottawa Scale (NOS). We used meta-analysis models to obtain the pooled two-dose VE, and the studies were divided into subgroups and analysed according to whether or not it was an outbreak investigation and its NOS score. The quality of evidence of VEs were rated by approach of the GRADE system.

RESULTS

A total of 12 studies and 87,196 individuals were included. The pooled two-dose VE was 90% (95% confidence interval [CI]: 69-97%). The VE of outbreak studies (87% [95% CI: 76-93%]) was lower than non-outbreak studies (99% [95% CI: 98-99%]). There was no significant difference in VEs by different NOS quality. The quality of the evidence assessment of pooled two-dose VE was "low", which was rated down by one category in limitations and publication bias respectively and rated up by two category in large effect. The quality of evidence assessment in subgroup of NOS score ≥ 7 was "moderate".

CONCLUSIONS

The VE of two-dose varicella vaccine is relatively high in preventing varicella, and is recommended for countries which need further control for varicella. However, higher quality evidence is needed as a supplement for stronger recommendations. The approach of GRADE could be applied for rating the quality of evidence in observational study.

Upgrading the school entry vaccination record check strategy to improve varicella vaccination coverage: results from a quasi-experiment study

BACKGROUND

The school entry vaccination record check strategy (SECS) is an appropriate opportunity to recommend vaccines for students to improve vaccination coverage (VC). However, it is only utilized for providing necessary catch-up vaccination for students who are missing the Expanded Program on Immunization (EPI) vaccines in China. We aimed to address that gap and quantify the relationship between the SECS policy and the increase of coverage in varicella vaccine (VarV).

METHODS

We employed a pretest and posttest quasi-experimental design to examine the effect of the upgraded SECS policy on the change of VarV coverage in newly enrolled students in Lu'an, 2019-2020.

RESULTS

Eight hundred participants were randomly divided into the control group (C group, 31.8%), the telephone-based intervention group (T group, 31.2%), and the written notification intervention group (W group, 37.0%). Totally, 84 students received VarV during the study period, with a VC of 10.5%. The possibility of vaccination in the T group (RR = 4.9, 95% CI:2.2-10.9) and W group (RR = 5.2, 95% CI:2.4-11.5) was significantly higher than that in the C group (p< .001).

CONCLUSIONS

Our study demonstrates that the upgraded SECS produce a positive effect on improving the VC of VarV. This nudge strategy may decrease varicella outbreaks in schools in China, especially in provinces where VarV is not introduced into EPI.

Effect of Earlier Vaccination and a Two-Dose Varicella Vaccine Schedule on Varicella Incidence - Beijing Municipality, 2007-2018

WHAT IS ALREADY KNOWN ABOUT THIS TOPIC?

The World Health Organization (WHO) varicella vaccines position paper states that countries where varicella is an important public health burden could consider introducing varicella vaccine (VarV) in the routine childhood immunization program (1). VarV has been available for many years in China but is not included in most routine immunization programs in China. As a result, substantial heterogeneity in vaccination coverage exists across regions.

WHAT IS ADDED BY THIS REPORT?

In Beijing, adding a second dose of VarV for children and increasing coverage reduced the incidence of varicella. Lowering the age of the first dose of VarV to 12 months could further reduce varicella, especially among toddlers.

WHAT ARE THE IMPLICATIONS FOR PUBLIC HEALTH PRACTICE?

Governments should use economic analysis to consider inclusion of VarV into the routine children immunization program as a free vaccine and adopting a 2-dose schedule that starts at 12 months of age.

Uptrend prevalence of varicella parallel with low serum antibodies and low second-dose rate among children 10-14 years old in Wenzhou, China

In recent years, the incidence of varicella cases is rising, and outbreaks of varicella are frequently being reported worldwide. Our study aims to analyze the association between the varicella incidence and serum antibody level in the post-vaccine era. We retrieved and analyzed the incidence and prevalence data for children age 1-14 years in Wenzhou, China during 2010-2018. A cross-sectional seroepidemiology analysis was carried out in a series of 168 general healthy children age 1-14 years as well as children at a varicella outbreak in Wenzhou. Our data showed a significant surge in the incidence and prevalence of varicella in children aged 10-14 years in 2017 and 2018 while they were kept relatively stable in 2010-2016. The seroepidemiological analysis revealed a 7.3-fold significantly higher level of serum varicella IgG in healthy control students who exposed at the outbreak than that in general healthy children (median 523.5 vs. 71.7 mIU/mL, p < .01). The children 10-14 years old had the lowest rate of second-dose vaccination among the three age classes (7%, 41%, and 65% in 10-14, 5-9, and 2-4 age class, respectively), and children 5-9 years old who received the second dose had a higher level of serum protective IgG than those who did not (254.7 vs 98 mIU/mL, p = .06). The findings from the present study warn a two-dose vaccine schedule to reduce the climbing incidence and prevalence observed in the older children and suggest a higher serum IgG threshold for effective protection of children from the varicella outbreak.

Assessing the Changes of Mumps Characteristics with Different Vaccination Strategies Using Surveillance Data: Importance to Introduce the 2-Dose Schedule in Quzhou of China

Background

From 2005 to 2016, the prevention and control of mumps in China have undergone three stages of transition. These include the use of MuCV as a self-supported vaccine, the introduction of one-dose MMR to the Expanded Program on Immunization (EPI), and the administration of two-dose MuCV following supplementary immunization activities (SIAs) using MM. Here, using surveillance data, we assessed the epidemiology of mumps during the three stages.

Methods

Children in Quzhou of China born from 2005 to 2016 and registered in the Zhejiang Provincial Immunization Information System (ZJIIS) were included. We analyzed the epidemic data and calculated incidence and MuCV coverage via birth cohorts.

Results

The average incidence of mumps in 2005-2006, 2007-2010, and 2011-2016 was 51.57, 41.02, and 12.53 per 100,000 individuals, respectively. The highest incidence was in children aged 6-14 years from 2005-2016, of which the majority were school students (67.84%). Approximately 90% of the reported outbreaks occurred in school children (primary school/middle school). The seasonal characteristics of mumps were less obvious from 2011 to 2016. The coverage of one-dose MMR in the 2005 birth cohort was 71.38%. For the 2006-2010 birth cohort, the coverage of one-dose MuCV was 96.82% and the coverage of two-dose MuCV was 17.68%. The children born from 2011 to 2016 were only free vaccinated with MMR; the coverage of one-dose MuCV was 99.10%. The mumps incidence in the three birth cohorts significantly declined (X² = 805.90, P < 0.001 for trend). Except the children less than two years old, the mumps incidence for the children born from 2006 to 2010 was higher than that for the children born from 2011 to 2016.

Conclusion

The mumps incidence significantly declined following the introduction of one-dose MMR. The SIA using MM led to a rapid reduction of mumps cases. Therefore, we recommend a two-dose MuCV routine immunization schedule and improved vaccination coverage.

Characteristics of within-household varicella transmission events associated with school outbreaks in Shanghai, China, 2009-2018

Transmission of varicella occurs frequently in schools and households. We investigated the characteristics of varicella cases derived from within-household transmission and the modes of varicella transmission between school and household settings in Shanghai, China, from 2009 to 2018. Within-household transmission occurred in 278 households, of which 134 transmission events were between children. Sixty-one household varicella transmission events may be attributed to isolation procedures for infected students during school outbreaks, and 7.6% of school outbreaks were caused by schoolchildren cases derived from within-household transmission. The frequency of ‘school-household-school’ transmission adds an additional layer of complexity to the control of school varicella outbreaks. Administration of varicella vaccine as post-exposure prophylaxis after exposure is considered to be an effective measure to control varicella spread within households and schools.

Seroprevalence and molecular characteristics of varicella-zoster virus infection in Chinese children

BACKGROUND

Varicella-zoster virus (VZV) infection in children is an important public health problem in China. We performed the current study to explore the seroprevalence of VZV infection in Chinese children in order to provide more information for improvement of varicella vaccination in China.

METHODS

Three thousand fourteen children were recruited from Chinese kindergarten students aged from four to six years. Anti-VZV IgG and IgM were assayed using enzyme-linked immunosorbent assay. Both ORF22 and ORF62 of VZV were amplified, sequenced, and analyzed by nested PCR.

RESULTS

Among 3014 children, 43.9% of boys and 46.3% of girls were vaccinated with varicella vaccine, respectively. The seroprevalence of anti-VZV IgG was 54.4% in the children with varicella vaccination, which was significantly higher than those in unvaccinated children (49.2%) (χ2 = 8.206, P = 0.004). Among of the vaccinated children, the detection rates of VZV IgG antibody increased with age, with 49.4, 50.9 and 58.9% in 4, 5 and 6-year groups, respectively (Trend χ2 = 17.202, P = 0.002). However, there was no difference in anti-VZV IgG detection rates among those unvaccinated children in different age groups (Trend χ2 = 8.681, P = 0.070). In addition, 13 boys and 13 girls were positive for anti-VZV IgM, respectively. Among of them, eight children (0.6%) have received varicella vaccination, which was similar to those in unvaccinated children (1.1%). However, only one ORF22 sequence was isolated from an unvaccinated 5-year boy. Compared to the reference VZV sequences, the nucleotide homology was estimated to be 99.7% with genotype J.

CONCLUSIONS

Our study indicated that about half of Chinese children aged four to six years have a high risk of VZV infection. It should be helpful for the evaluation on the necessity of varicella immunization in China.

Are providers' recommendation and knowledge associated with uptake of optional vaccinations among children? A multilevel analysis in three provinces of China

BACKGROUND

Immunization services providers play a crucial role in the successful implementation of immunization, particularly for new vaccines. Several childhood vaccinations that are important for public health are not included in the National Immunization Programme in China, although they are available as optional and self-paid vaccines. Their coverage remains low.

OBJECTIVE

To examine the association between providers' knowledge and recommendations of optional vaccines, as well as other supply- and demand-side factors, and their uptake among children.

METHODS

A cross-sectional study, that included an in-person questionnaire survey for parents of children under-3 years and a self-administrative questionnaire survey for their vaccination services providers, was conducted in 36 townships or sub-districts in three provinces of China in 2013. Using a sample of 1791 household from 30 townships or sub-districts, we applied multilevel logistic analyses to examine the factors associated with the uptake of optional vaccines based on a hierarchal framework that combined demand-side and supply-side factors.

RESULTS

Coverage of optional childhood vaccinations varied across small areas. Supply- and demand-side factors were both associated with the uptake of these vaccines. Immunization services providers' recommendations and their knowledge about optional vaccination were positively and significantly associated with uptake. Children were more likely to receive the vaccines if they lived in communities with higher immunization worker density or larger immunization clinics. Several demand-side psychological factors about childhood vaccination were also associated with optional vaccinations.

CONCLUSIONS

Promoting immunization services providers to conduct evidence-based recommendations about some important childhood optional vaccinations and enhancing their knowledge regarding optional vaccinations and communication skills are useful strategies to increase the coverage of these vaccinations.

Effectiveness of post-exposure prophylaxis during varicella outbreaks among primary and middle school students in Shanghai: An analysis of three-year surveillance data

OBJECTIVES

To evaluate the effectiveness of post-exposure prophylaxis conducted during varicella outbreaks among students in Shanghai.

METHODS

Surveillance data were collected from September 1, 2013 to December 31, 2016 involving 3524 susceptible students in 109 primary and middle school classes where emergency vaccinations (EVs) had been administered. Students were divided into two groups according to their prior vaccination (PV) varicella vaccine status. A secondary attack rate was used to compare EV and non-EV groups using a chi-squared test. Stratification analyses were performed, adjusting for the EV administration date, the vaccination coverage rate, and the number of cases prior to the EV.

RESULTS

The effectiveness rate was 92.2% (95% confidence interval (CI): 37.1-99.0%) when EV was applied within 3 days following the outbreak onset date, and 95.2% (95% CI: 79.9-98.8%) when vaccination coverage was ≥80% among students with PV. When students with PV received an EV for varicella within 3 days, the effectiveness rate was 100%.

CONCLUSIONS

EV showed high protective effectiveness for varicella during outbreaks, especially if administered within 3 days of an outbreak and in conjunction with a high coverage rate.

Knowledge, Attitude and Practice of Pregnant Women towards Varicella and Their Children's Varicella Vaccination: Evidence from Three Distrcits in Zhejiang Province, China

Background: The objectives of this study were to examine the knowledge, attitudes and practice (KAP) towards varicella and varicella vaccine (VarV) vaccination among pregnant women in three distrcits in Zhejiang Province, China. Methods: From 1 January to 31 March 2014, pregnant women with ≥12 gestational weeks were recruited and received a self-administrated questionnaire. The first dose of VarV (VarV1) vaccination status of children from present pregnancy was extracted at 24 months of age from Zhejiang provincial immunization information system (ZJIIS). Three variables was defined as the main outcomes, which included: (1) knowing about both the availability of VarV and the number of doses required; (2) positive attitude towards the utility of varicella vaccination; (3) the vaccination coverage of VarV1, which meant the proportion of children having received the VarV1. Counts and proportions were used to describe the socio-demographic characteristics of study participants, and their relationship with study outcomes were tested using chi-square tests in univariate analysis and logistic regression in multivariable analysis. Results: A total of 629 pregnant women participated in this study. The majority of the participants (68.0%) answered correctly about the transmission route of varicella. The proportion of participants who heard about varicella vaccination was 76.5% and 66.8% knew that VarV was currently available. Only 13.5% of the participants answered correctly that the complete VarV series needed two doses. Age, immigration status, education level, household income, and number of children of the pregnant women were significant predictors of the KAP regarding the VarV vaccination. Conclusions: The current survey indicated that optimal KAP levels and coverage on VarV vaccination were observed in three districts of Zhejiang Province. Health education programs on varicella and VarV vaccination directed towards both pre-natal and post-natal women are needed, which will result in a better attitude on vaccination of VarV and in a high coverage of VarV.

Timeliness of Childhood Primary Immunization and Risk Factors Related with Delays: Evidence from the 2014 Zhejiang Provincial Vaccination Coverage Survey

Background: this study aimed to assess both immunization coverage and timeliness, as well as reasons for non-vaccination, and identity the risk factors of delayed immunization, for the vaccines scheduled during the first year of life, in Zhejiang province, east China. Methods: A cluster survey among children aged 24-35 months was conducted. Demographic information and socio-economic characteristics of the selected child, the mother, and the household were collected. Immunization data were transcribed from immunization cards. Timeliness was assessed with Kaplan-Meier analysis for each vaccine given before 12 months of age, based on the time frame stipulated by the expanded program on immunization of China. Cox proportional hazard regression was applied to identify risk factors of delayed immunization. Results: A total of 2772 eligible children were surveyed. The age-appropriate coverage ranged from 25.4% (95% CI: 23.7-27.0%) for Bacillus Calmette-Guerin (BCG) to 91.3% (95% CI: 90.2-92.3%) for the first dose of oral poliomyelitis vaccine (OPV1). The most frequent reason for non-vaccination was parent's fear of adverse events of immunization. Delayed immunizations were associated with mother having a lower education level, mother having a job, delivery at home, increasing number of children per household, and having a lower household income. Conclusions: Although the timeliness of immunization has improved since 2011, necessary steps are still needed to achieve further improvement. Timeliness of immunization should be considered as another important indicator of expanded program on immunization (EPI) performance. Future interventions on vaccination coverage should take into consideration demographic and socio-economic risk factors identified in this study. The importance of adhering to the recommended schedule should be explained to parents.

Evaluating Childhood Vaccination Coverage of NIP Vaccines: Coverage Survey versus Zhejiang Provincial Immunization Information System

Vaccination coverage in Zhejiang province, east China, is evaluated through repeated coverage surveys. The Zhejiang provincial immunization information system (ZJIIS) was established in 2004 with links to all immunization clinics. ZJIIS has become an alternative to quickly assess the vaccination coverage. To assess the current completeness and accuracy on the vaccination coverage derived from ZJIIS, we compared the estimates from ZJIIS with the estimates from the most recent provincial coverage survey in 2014, which combined interview data with verified data from ZJIIS. Of the enrolled 2772 children in the 2014 provincial survey, the proportions of children with vaccination cards and registered in ZJIIS were 94.0% and 87.4%, respectively. Coverage estimates from ZJIIS were systematically higher than the corresponding estimates obtained through the survey, with a mean difference of 4.5%. Of the vaccination doses registered in ZJIIS, 16.7% differed from the date recorded in the corresponding vaccination cards. Under-registration in ZJIIS significantly influenced the coverage estimates derived from ZJIIS. Therefore, periodic coverage surveys currently provide more complete and reliable results than the estimates based on ZJIIS alone. However, further improvement of completeness and accuracy of ZJIIS will likely allow more reliable and timely estimates in future.

Auditing the Immunization Data Quality from Routine Reports in Shangyu District, East China

Objective: To evaluate the immunization data quality in Shangyu District, East China. Methods: An audit for immunization data for the year 2014 was conducted in 20 vaccination clinics of Shangyu District. The consistency of immunization data was estimated by verification factors (VFs), which was the proportion of vaccine doses reported as being administered that could be verified by written documentation at vaccination clinics. The quality of monitoring systems was evaluated using the quality index (QI). Results: The VFs of 20 vaccine doses ranged from 0.94 to 1.04 at the district level. The VFs for the 20 vaccination clinics ranged from 0.57 to 1.07. The VFs for Shangyu District was 0.98. The mean of total QI score of the 20 vaccination clinics was 80.32%. A significant correlation between the VFs of the 3rd dose of the diphtheria-tetanus-pertussis combined vaccine (DTP) and QI scores was observed at the vaccination clinic level. Conclusions: Deficiencies in data consistency and immunization reporting practice in Shangyu District were observed. Targeted measures are suggested to improve the quality of the immunization reporting system in vaccination clinics with poor data consistency.

Two-dose seasonal influenza vaccine coverage and timeliness among children aged 6 months through 3 years: An evidence from the 2010-11 to the 2014-15 seasons in Zhejiang province, east China

OBJECTIVE

To evaluate the coverage and timeliness of seasonal influenza vaccine vaccination (SIV) among children aged 6 months to 3 years from the 2010-11 through the 2014-15 seasons.

METHODS

Children registered in Zhejiang Provincial Immunization Information System (ZJIIS) and needed 2 seasonal influenza vaccine doses in a given season from 2010-11 to 2014-15 were enrolled. Socio-economic information and SIV records of target children were extracted from ZJIIS on 1 January 2016. Any (≥1 dose) and full (2 doses) vaccination coverage by December 1 and March 31 as well as interval between 2 doses were calculated. Trends of coverage over time and determinants on fully vaccination coverage and interval between 2 doses were assessed.

RESULTS

Full SIV overage by Mar 31 increased from the 2010-11 to the 2014-15 seasons (2.60% vs 2.92%). Less than 1% of children received 2 doses by December 1. The interval between 2 doses among fully vaccinated children decreased over time (2010-11: 68.32 days; 2014-15: 49.51 days; p < 0.05). Age, socio-economic development level of resident areas were inversely associated with full vaccination coverage and resident children had a significantly higher full vaccination coverage. Younger age, resident children, receiving vaccination from higher service frequency clinics and clinics with morning and afternoon sessions were positive determinants of a shorter interval between 2 doses.

CONCLUSION

Majority of children aged 6 months to 3 years remained at risk of incomplete and delayed SIV. The importance of the 2-dose SIV recommendation needs to be emphasized and effective interventions needs to be implemented to improve the completeness and the timeliness of SIV.