This chapter will present critical appraisal of the selected articles included in this study using the Critical Appraisal Skill Program (CASP) adapted from Public Health Resource Unit of the National Health Service (NHS), UK and a quantitative appraisal tool adapted from the University of Salford, UK. It will also present the findings of the retrieved studies on the factors affecting polio immunization in Nigeria positively or negatively.
The studies included are as follows:
2 Case-control studies
3 Qualitative studies and
5 Quantitative studies
The table below presents the summary of included and excluded studies.
Database
Number of studies retrieved
Included studies
Excluded studies
AMED
CINAHL
MEDLINE
180
350
500
2
4
14
178
346
486
TOTAL
1030
20
1010
After an extensive search, 20 studies were included initially, however when the studies were critically appraised 10 studies did not meet the quality of a good study and they were then excluded leaving only 10 studies which were then appraised.
The tables below illustrate the critical appraisal of included studies.
Jenkins et al (2008)
Yes, the study addressed a clearly focused issue which was the estimate of the field efficacies of monovalent type 1 and oral poliovirus vaccine in children with acute flaccid paralysis caused by poliovirus and a matched control of children with acute flaccid paralysis not caused by poliovirus
Yes, the authors recruited cases with a matched control to test the efficacy of monovalent and trivalent oral polio vaccine. Therefore, a case-control study is appropriate
Yes, the cases were defined precisely and they represent a defined population (Nigeria). Furthermore, a total of 21,815 cases were recruited and were confirmed subject to clinical, epidemiological and laboratory investigations
Yes, the controls were selected in an acceptable way as the cases and they were matched in a 1:1 ratio. Furthermore, the matching was based on age and region and there was no evidence of selection bias as controls were selected randomly
Yes, the measurement of exposure between cases and controls was similar because all cases of acute flaccid paralysis were investigated before confirmation of poliovirus status ensuring blinding of the researchers and parents/guardians of the children recruited during dose-response interviews which minimized the risk of systematic bias
The authors accounted for environmental factors as confounding factors. However, the authors should have considered socioeconomic factors such as education and income level. Nevertheless, the authors have taken into account of the potential confounding factors in their analysis using a conditional logistic-regression analysis of the 1:1 matched data
In line with the aim of the study, the authors stated that; the estimated efficacy of trivalent oral poliovirus vaccine against paralysis from type 1 poliomyelitis across Nigeria to be 16% (95% confidence interval [CI] 10-21) per dose, and efficacy against type 3 was 18% (95% CI 9-26). The efficacy of monovalent oral polio vaccine against type 1 to be 67% (95% CI 39-82)
The P value of the results is stated to be (p<0.001) in each case. On the other hand it was stated clearly that the probability of misclassifying a case was p=0.0011 for type 1 poliovirus and p=0.0006 for type 3 poliovirus
Yes, due to higher matching of cases and controls and sensitivity analyses carried out by the authors, the results can be said to be robust. Furthermore, the authors assessed the validity of reporting constant efficacy per dose of vaccine by means of a likelihood-ratio test
Yes, the subjects covered by the study represents the whole study area (Nigeria) because the authors considered recruiting subjects from all the six geo-political zones of the country
Yes, there was similar evidence from another study conducted in India (which is another polio endemic country as evidenced by the literature)
Jenkins et al (2010)
Yes, the study addressed a clearly focused issue which was implications of a circulating vaccine derived poliovirus in Nigeria where they identified cases of acute flaccid paralysis associated with fecal excretion of type 2 circulating vaccine derived poliovirus (cVDPV), type 1 wild poliovirus (WPV), or type 3 WPV in which the clinical characteristics of these cases, clinical attack rates for each virus, and the effectiveness of oral poliovirus vaccine in preventing paralysis from each virus were compared
Yes, the authors recruited cases of acute flaccid paralysis associated with fecal excretion of type 2 cVDPV, type 1 WPV or type 3 WPV and compared them with suitable controls on the basis of age, date of onset of the paralysis and residence. Therefore, a case-control study is appropriate to address the issue
Yes, the cases were defined precisely based on having acute flaccid paralysis using clinical, epidemiologic and laboratory investigations. Furthermore, they represent a defined population of children younger than 15 years of age in Nigeria
Yes, the controls were selected in an acceptable way as they were matched with the cases in a 1:1 ratio and the matching was based on the same criteria of recruiting the cases as mentioned earlier
Yes, the measurement methods in cases and controls were similar because both subjects were subjected to clinical, epidemiologic and laboratory investigation before categorizing
The authors stated socio-economic factors as possible confounding factors but applied a regression model to control the confounders
The bottom line result of the study was that the cases of acute flaccid paralysis with type 2 cVDPV were broadly similar to those with type 1 WPV or type 3 WPV in terms of the distribution of age and sex and there were no significant differences in the severity of the clinical disease
The estimated effectiveness of a dose of trivalent oral poliovirus vaccine was greater against paralysis resulting from type 1 WPV (p=0.04) and type 3 WPV (p=0.12). Furthermore, the authors added that serotype 1 monovalent oral polio vaccine was significantly more protective than trivalent oral polio vaccine against paralysis from type 1 WPV (p<0.001) and serotype 3 monovalent oral polio vaccine was non-significantly more protective than trivalent oral poliovirus vaccine against paralysis from type 3 WPV (p=0.08)
Yes, tighter matching of cases and controls and also matching of the cases and controls (subjects) based on district rather than state resolved systematic bias and enables the results to be robust
Yes, the subjects recruited for the study represent the study area (Nigeria) because the authors recruited from all six geo-political zones of the country
The findings of the study is said to be consistent with the higher rates of sero-conversion to cVDPV observed after administration of trivalent oral polio vaccine in other developing countries
Renne (2006)
Yes, the author aimed at examining the reasons for the difficulties in eradicating polio in Northern Nigeria.
Yes, examining people’s perception on a particular health issue requires a qualitative approach.
Yes, evaluating people’s perception can be achieved using a qualitative approach.
Yes, it is appropriate because the recruitment strategy which is snow-ball sampling will enable the researcher to identify the participants affected by polio immunization.
Yes, the method of data collection stated included: participant observation, open-ended interviews by a snow-ball sampling, and collection of polio-related documents.
No, there was no evidence of reflexivity
Yes, the issue of confidentiality was considered. However, the author did not state evidence of consent taken and ethical clearance from an ethical research committee having dealt with human subjects.
Yes, the data collection was rigorous evidenced by verbatim quoting and transcription of different codes.
Yes, political will, low level of education, improper training of health workers, religious belief, public distrust, ethnicity, health inequity, breakdown of primary health care clinics and hospitals at local levels affect polio immunization uptake.
The findings were related to both current practice and relevant research-based literature.
Oluwadare (2009)
Yes, the study was aimed at explaining the intractable plummeting trend of immunisation in Nigeria and in Ekiti State as a case study
Yes, the author employed the use of focus groups interviews, key informant interviews, and semi-structured interviews for data collection, therefore, a qualitative methodology is appropriate
Yes
Yes, the author recruited a mix of population groups residing in the study area and it is suitable (necessary) in achieving the set aim of the study
Yes
No, there was no evidence
No, despite using human subjects there was no evidence of ethical approval stated by the author
Yes, there is evidence of verbatim quoting which can confer rigour to the study
Yes, area of settlement (rural/urban factor), bad road networks and poor vaccine supplies were the factors that affect immunisation uptake in the study area
The findings were related to relevant research based literature
Babalola & Adewuyi (2005)
Yes, the aim of the research was to identify demand side factors that influence immunization uptake in Nigeria and make recommendations to policy makers
Yes, a qualitative methodology can be deemed appropriate in addressing the above aim of the research and considering the fact that interviews were administered, it is appropriate
Yes
The recruitment strategy is OK because participants were recruited from five of the six-geo-political zones of the country. However, one of the regions was left out. Nonetheless, the recruitment strategy could enable the authors achieve their set aim
Yes
No, there was no evidence of reflexivity
No, there was no detail of how ethical approval was sought nor the issues around informed consent or confidentiality
Yes, there was use of thematic analysis and the themes were derived from the data
Yes, socio-demographic factors such as; poverty, religion, accessibility, low literacy level, place of birth (rural or urban), personal efficacy, myths and rumours. Vaccine availability, coverage, and efficacy were also among the key issues affecting immunization uptake
The findings from the study provide important information about immunization practices in Nigeria- because the survey was theory-based and will enable easy establishment of scientific sound bias for programming
Antai (2009)
The aim of the study was to assess the individual-level determinants of full immunization, by sequentially controlling for explanatory factors; and determine whether community-level explanatory factors account for variations in full immunization
The key findings are: deficiency in vaccine supplies, inequitable access to immunization services, and socio-economic status
Quantitative
Strengths: statistical methods used that control the potential confounding variables, there was triangulation in the study; with nested case-control, normalised sample weights were clearly stated to be used in all analyses to adjust for non-response and enable generalisation of the findings to the general population
Weaknesses: there is possibility for recall bias; because while gathering the data, in cases of absence of vaccination cards, mothers were asked to recall whether their child had received the vaccinations
Nigeria, Africa
The inclusion criteria was: children under 5 years of age and females aged 15-49
The exclusion criteria was: children above 5 years of age and females younger or above 15-49 years
The sample was selected using stratified two-stage cluster sampling procedure
7864
Normalised sample weights were clearly stated to be used in the analyses to adjust for non-response and enable generalisation of the findings to the general population. Therefore, sample size was sufficient
Majority of the participants were children under 5 years of age and females aged 15-49 and the participants represent each class of income or socio-economic status and share a particular location; the study area.
Yes, ethical issues were fully considered and informed consent of the participants prior to commencement of the study was sought
Statistically using stratified two-stage cluster sampling procedure and multilevel multivariate regression analysis
Yes, Level of education of mothers; low OR=0.75 (95% CI 0.55-1.06), middle OR=1, high OR=1.02 (95% CI 0.73-1.41), Community hospital delivery; low OR=0.62 (95% CI 0.40-0.94), middle OR=1, high OR=1.12 (95% CI 0.75-1.68), Wealth index; poorest OR=0.35 (95% CI 0.21-0.59), poorer OR=0.47 (95% CI 0.27-0.81), middle OR=0.64 (95% CI 0.42-0.97), richer OR=0.57 (95% CI 0.37-0.84), richest OR=1
This study can be generalised to the study area because the author considered participants from different regions, levels of education, wealth quintile as well as community hospital delivery.
Antai (2010)
The aim of the study was to examine the effects of individual and community level characteristics of migrant groups on the likelihood of the full immunization uptake of their children in Nigeria
The key findings are: widespread disparities in immunization coverage between regions, socioeconomic, demographic, and cultural factors, and population migration from rural to urban areas
Quantitative
Strengths: statistical methods used that control the possible confounding variables there was also triangulation in the study; with nested case control
Weaknesses: there was room for recall bias while gathering the data
Nigeria, Africa
The inclusion criteria was: children under 5 years of age and females aged 15-49
The exclusion criteria was: children above 5 years of age and females younger or above 15-49 years
The sample was selected using stratified two-stage cluster sampling procedure
The author stated that a total of 6029 children were nested within 3725 mothers who were in turn nested within 365 communities
Yes
Majority of the participants were children under 5 years of age and females aged 15-49 and the participants represent each class of income or socio-economic status and share a particular location; the study area.
Yes, ethical issues were fully considered and informed consent of the participants prior to commencement of the study was sought
The author stated the potential confounding variable to be child-and mother-level characteristics and they were controlled using stratification and multilevel multivariate regression analyses
Yes, mothers age; 15-18 OR=0.50 (95% CI 0.22-1.12), 19-23 OR=0.81 (95% CI 0.54-1.21), 24-28 OR = 1, 29-33 OR= 1.08 (95% CI 0.75-1.55) ≥ 34 OR=1.54 (95% CI 1.03-2.30), mothers’ level of education; no education OR=0.72 (95% CI 0.50-1.03), primary OR=0.97 (95% CI 0.69-1.36), secondary or higher OR=1, wealth index: poorest OR=0.45 (95% CI 0.26-0.77), poorer OR=0.43 (95% CI 0.26-0.70), middle OR=0.62 (95% CI 0.41-0.95), richer OR=0.54 (95% CI 0.37-0.78), richest OR=1
This study can be generalised to the study area because the author considered participants from different regions, level of education, and wealth quintile
Ngowu et al (2008)
The aim of the study was to assess the outcome of expanded program on immunisation in Nigeria as well as to examine systemic factors influencing its high under five mortality rates
The key findings of the study are: low literacy rates, and inadequate spending on health care
Quantitative
Strengths: the use of statistical model which was multiple regression with auto-correlation adjustment methods to control the potential confounding factors, and evidence of no missing data was clearly stated
Weaknesses: There is no evidence of controlling or adjusting bias in the study
Nigeria, Africa
Not clearly stated
Not clearly stated
Not clearly stated
The authors dealt with data from reliable survey sources and did not clearly state the number or sample size
Can’t tell, based on the use of survey data from other sources
All surveys carried out in relation to immunization programs in Nigeria
Yes, permission for all information obtained were sought
The authors did take into account potential confounders to be corruption, instability in government, tribal resistance to immunization ion rural areas, and technical problems in delivering vaccines to remote areas. However, the statistical models employed in the study which is multiple regression with auto-correlation adjustment have taken care of the confounders
Yes, the results show that literacy rate is inversely related to the under five mortality rate and is statistically significant at 99% (p<0.001) and is consistent with both theory and previous works, the results also stated that the primary health care plan had a relationship to under five mortality rate and the result is statistically significant at 99.9% (p<0.001)
The findings of this study can be generalised to the study area due to the credible sources of the primary data, and due to the hypotheses generated and analysed
Odusanya et al (2008)
The aim of the study was to assess vaccination coverage for childhood vaccines and maternal factors impacting coverage in a rural community of Sabongida-Ora in Edo State, Nigeria
Maternal factors were most strongly associated with non-completion of vaccination, the most frequent was lack of awareness of the need for immunization, and the sensitivity and accuracy of maternal recall of adequacy of vaccination showing it may be possible to rely on maternal history to determine vaccination coverage in the community the study was carried out
Quantitative
Strengths: sample size calculation methodology was stated, clear statement of inclusion and exclusion criteria, sensitivity analyses and multiple logistic regression method to control potential confounders, the use of spinning-bottle method in data collection will help control selection bias
Weaknesses: there was no mention of how interviewer bias was controlled despite using interviewer-administered questionnaire as the survey instrument
Nigeria, Africa
Mothers/caregivers who live in and around Sabongida-Ora and have children who were born between 01/10/2004 and 31/08/2005 (12-13 years old)
Subjecs whose ages were outside the eligible age group and those with incomplete vaccination records were excluded from the data analysis
The sample was selected using spinning bottle method
339 mothers and 339 children (each mother had an eligible child)
The sample size calculation methodology stated by the authors was that of WHO immunization coverage cluster survey reference manual and the number of children required from the study area was 312 and 339 children were recruited. Therefore, the sample size is sufficient
Mothers/caregivers who live in and around Sabongida-Ora and have children who were 12-13 years old
Yes, the ethical approval was granted by the ethics committee of Ambrose Alli University College of medicine and also from the community leaders. Furthermore, consent was obtained from the eligible mothers/caregivers included
The authors acknowledged maternal education to be among the confounding variable and it was controlled by statistical model analyses
Yes, the results present education level of mothers; none/primary OR=1, secondary/University (OR=1.79 95% CI =0.97-3.31) (p=0.064), knowledge score categorized; poor OR=1, satisfactory OR=0.31 (95% CI=0.13-0.72) (p=0.006), place of vaccination Glaxo Smith Kline OR=30.39 (95% CI=14.12-65.42) (p<0.001) Government/Private OR=1
The findings of this study can be applied to rural areas of mid-western Nigeria because residents share common characteristics and such studies need to be repeated in other parts of the country for more generalisability
Adeyinka et al (2009)
The study aimed at determining the awareness and attitude of mothers of under-five towards immunization and proportion of children fully immunized in the 12-28 months
Long waiting queues, payment at private clinics, distance, were the key findings of the study and the authors concluded that lack of political will, lack of motivation, and infrastructure are the factors attributed low level of immunization in Nigeria
Quantitative
Strengths: the use of random cluster sampling, recruitment strategy will help control selection bias, clear statement of methodology, clear inclusion and exclusion criteria, ethical consideration
Weaknesses: there was no mention of how interviewer bias was controlled despite using interviewer-administered questionnaire as the survey instrument
Nigeria, Africa
Mothers with children under-5 years of age born between 12th February to 6th April, 2008
Mothers with children under-5 years of age not born between 12th February to 6th April, 2008
The sample was selected using cluster random sampling technique
503
Based on the sample size calculation 124 mothers was the minimum sample size
Mothers with children under-5 years of age born between 12th February to 6th April, 2008 who live in around Igbo-Ora, Oyo State, Nigeria
Yes, permission to administer questionnaires was obtained at the various centers and a verbal consent was obtained from the respondents after they had been fully counseled about the study via a written consent
The potential confounding variables were controlled using multi-variate analysis
Yes, the measures were well validated using statistical tests; Chi-square test, fisher exact test for categorical variables while T-test was used to compare means of continuous variables and logistic regression for multi-variate analysis. Overall, the level of statistical significance was p=0.05
The findings of this study can be applied to rural areas of south-western Nigeria because residents share common characteristics. However, studies need to be repeated in other parts of the country for more generalisability.
In this section, the author seeks to explain the various studies used in the thematic analysis thereby highlighting their strengths, weaknesses, and score the articles according to the screening questions in the appraisal tools (methodological scoring).
A case-control study is an observational epidemiological study that measures and compares the prevalence of exposure to a factor among persons with an outcome of interest (cases) and a suitable group of persons without that particular outcome (control). If the prevalence of exposure is higher in the cases than in the controls, the exposure might be a risk factor for the outcome. If it is lower, the exposure might be a protective factor for the outcome. (Porta, 2008; Rothman et al, 2008)
Case-control studies are applicable to chronic diseases, infectious diseases and injuries, and evaluating population-based interventions (Friis & Sellers, 2004). With respect to this research, Jenkin
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