52 research outputs found
Monitoring vaccination coverage: Defining the role of surveys.
Vaccination coverage is a widely used indicator of programme performance, measured by registries, routine administrative reports or household surveys. Because the population denominator and the reported number of vaccinations used in administrative estimates are often inaccurate, survey data are often considered to be more reliable. Many countries obtain survey data on vaccination coverage every 3-5years from large-scale multi-purpose survey programs. Additional surveys may be needed to evaluate coverage in Supplemental Immunization Activities such as measles or polio campaigns, or after major changes have occurred in the vaccination programme or its context. When a coverage survey is undertaken, rigorous statistical principles and field protocols should be followed to avoid selection bias and information bias. This requires substantial time, expertise and resources hence the role of vaccination coverage surveys in programme monitoring needs to be carefully defined. At times, programmatic monitoring may be more appropriate and provides data to guide program improvement. Practical field methods such as health facility-based assessments can evaluate multiple aspects of service provision, costs, coverage (among clinic attendees) and data quality. Similarly, purposeful sampling or censuses of specific populations can help local health workers evaluate their own performance and understand community attitudes, without trying to claim that the results are representative of the entire population. Administrative reports enable programme managers to do real-time monitoring, investigate potential problems and take timely remedial action, thus improvement of administrative estimates is of high priority. Most importantly, investment in collecting data needs to be complemented by investment in acting on results to improve performance
Bayesian hierarchical modelling approaches for combining information from multiple data sources to produce annual estimates of national immunization coverage
Estimates of national immunization coverage are crucial for guiding policy
and decision-making in national immunization programs and setting the global
immunization agenda. WHO and UNICEF estimates of national immunization coverage
(WUENIC) are produced annually for various vaccine-dose combinations and all
WHO Member States using information from multiple data sources and a
deterministic computational logic approach. This approach, however, is
incapable of characterizing the uncertainties inherent in coverage measurement
and estimation. It also provides no statistically principled way of exploiting
and accounting for the interdependence in immunization coverage data collected
for multiple vaccines, countries and time points. Here, we develop Bayesian
hierarchical modeling approaches for producing accurate estimates of national
immunization coverage and their associated uncertainties. We propose and
explore two candidate models: a balanced data single likelihood (BDSL) model
and an irregular data multiple likelihood (IDML) model, both of which differ in
their handling of missing data and characterization of the uncertainties
associated with the multiple input data sources. We provide a simulation study
that demonstrates a high degree of accuracy of the estimates produced by the
proposed models, and which also shows that the IDML model is the better model.
We apply the methodology to produce coverage estimates for select vaccine-dose
combinations for the period 2000-2019. A contributed R package {\tt imcover}
implementing the No-U-Turn Sampler (NUTS) in the Stan programming language
enhances the utility and reproducibility of the methodology.Comment: 31 pages (main), 4 figure
Factors affecting age-appropriate timeliness of vaccination coverage among children in Lebanon [version 1; referees: 2 approved]
Background: The effect of immunization does not only depend on its completeness, but also on its timely administration. Routine childhood vaccinations schedules recommend that children receive the vaccine doses at specific ages. This article attempts to assess timeliness of routine vaccination coverage among a sub-sample of children from a survey conducted in 2016. Methods: This analysis was based on data from a cross-sectional multistage cluster survey conducted between December 2015 and June 2016 among caregivers of children aged 12-59 months in all of Lebanon using a structured survey questionnaire. The analysis used KaplanâMeier curves and logistic regression to identify the predictors of age-appropriate immunization. Results: Among the 493 randomly selected children, timely administration of the third dose of polio vaccine, diphtheria-tetanus-pertussis (DTP)-containing vaccine and hepatitis B (HepB) vaccine occurred in about one-quarter of children. About two-thirds of children received the second dose of a measles-containing vaccine (MCV) within the age interval recommended by the Expanded Programme on Immunization (EPI). Several factors including socio-demographic, knowledge, beliefs and practices were found to be associated with age-appropriate vaccination; however, this association differed between the types and doses of vaccine. Important factors associated with timely vaccination included being Lebanese as opposed to Syrian and being born in a hospital for hepatitis B birth dose; believing that vaccination status was up-to-date was related to untimely vaccination. Conclusions: The results suggest that there is reason for concern over the timeliness of vaccination in Lebanon. Special efforts need to be directed towards the inclusion of timeliness of vaccination as another indicator of the performance of the EPI in Lebanon
Factors Associated with Reported Diarrhoea Episodes and Treatment-seeking in an Urban Slum of Kolkata, India
In an urban slum in eastern Kolkata, India, reported diarrhoea rates,
healthcare-use patterns, and factors associated with reported diarrhoea
episodes were studied as a part of a diarrhoea-surveillance project.
Data were collected through a structured interview during a census and
healthcare-use survey of an urban slum population in Kolkata. Several
variables were analyzed, including (a) individual demographics, such as
age and educational level, (b) household characteristics, such as
number of household members, religious affiliation of the household
head, building material, expenditure, water supply and sanitation, and
(c) behaviour, such as hand-washing after defecation and healthcare
use. Of 57,099 study subjects, 428 (0.7%) reported a diarrhoea episode
sometime during the four weeks preceding the interview. The strongest
independent factors for reporting a history of diarrhoea were having
another household member with diarrhoea (adjusted odds ratio [OR]=3.8;
95% confidence interval [CI] 3.3-4.4) and age less than 60 months
(adjusted OR=3.7; 95% CI 3.0-4.7). The first choice of treatment by the
428 subjects was as follows: 151 (35%) had self- or parent-treatment,
150 (35%) consulted a private allopathic practitioner, 70 (16%) went
directly to a pharmacy, 29 (7%) visited a hospital, 14 (3%) a
homoeopathic practitioner, 2 (0.5%) an ayurvedic practitioner, and 12
(3%) other traditional healers. The choices varied significantly with
the age of patients and their religion. The findings increase the
understanding of the factors and healthcare-use patterns associated
with diarrhoea episodes and may assist in developing public-health
messages and infrastructure in Kolkata
The Role of Epidemiology in the Introduction of Vi Polysaccharide Typhoid Fever Vaccines in Asia
Despite the availability of at least two licensed typhoid fever
vaccines-injectable sub-unit Vi polysaccharide vaccine and live, oral
Ty21a vaccine-for the last decade, these vaccines have not been widely
introduced in public-health programmes in countries endemic for typhoid
fever. The goal of the multidisciplinary DOMI (Diseases of the Most
Impoverished) typhoid fever programme is to generate policy-relevant
data to support public decision-making regarding the introduction of Vi
polysaccharide typhoid fever immunization programmes in China, Viet
Nam, Pakistan, India, Bangladesh, and Indonesia. Through
epidemiological studies, the DOMI Programme is generating these data
and is offering a model for the accelerated, rational introduction of
new vaccines into health programmes in low-income countries. Practical
and specific examples of the role of epidemiology are described in this
paper. These examples cover: (a) selection of available typhoid fever
vaccines to be introduced in the programme, (b) generation of
policy-relevant data, (c) providing the 'backbone' for the
implementation of other multidisciplinary projects, and (d) generation
of unexpected but useful information relevant for the introduction of
vaccines. Epidemiological studies contribute to all stages of
development of vaccine evaluation and introduction
Expansion of seasonal influenza vaccination in the Americas
<p>Abstract</p> <p>Background</p> <p>Seasonal influenza is a viral disease whose annual epidemics are estimated to cause three to five million cases of severe illness and 250,000 to 500,000 deaths worldwide. Vaccination is the main strategy for primary prevention.</p> <p>Methods</p> <p>To assess the status of influenza vaccination in the Americas, influenza vaccination data reported to the Pan American Health Organization (PAHO) through 2008 were analyzed.</p> <p>Results</p> <p>Thirty-five countries and territories administered influenza vaccine in their public health sector, compared to 13 countries in 2004. Targeted risk groups varied. Sixteen countries reported coverage among older adults, ranging from 21% to 100%; coverage data were not available for most countries and targeted populations. Some tropical countries used the Northern Hemisphere vaccine formulation and others used the Southern Hemisphere vaccine formulation. In 2008, approximately 166.3 million doses of seasonal influenza vaccine were purchased in the Americas; 30 of 35 countries procured their vaccine through PAHO's Revolving Fund.</p> <p>Conclusion</p> <p>Since 2004 there has been rapid uptake of seasonal influenza vaccine in the Americas. Challenges to fully implement influenza vaccination remain, including difficulties measuring coverage rates, variable vaccine uptake, and limited surveillance and effectiveness data to guide decisions regarding vaccine formulation and timing, especially in tropical countries.</p
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