Survey of poliovirus antibodies during the final stage of polio eradication in Egypt

Nutritional Status Link with Polioseronegativity Among Children from Poliomyelitis Transmission High-Risk Area of the Democratic Republic of the Congo (DRC)

Background

Malnutrition is identified as a risk-factor for insufficient polioseroconversion in the context of a vaccine-derived polio virus (VDPV) outbreak prone region. To assess the prevalence of malnutrition and its link to poliovirus insufficient immunity, a cross-sectional household survey was conducted in the regions of Haut- Lomami and Tanganyika, DRC.

Methods

In March 2018, we included 968 healthy children aged 6 to 59 months from eight out of 27 districts. Selection of study locations within these districts was done using a stratified random sampling method, where villages were chosen based on habitat characteristics identified from satellite images. Consent was obtained verbally in the preferred language of the participant (French or Swahili) by interviewers who received specific training for this task. Furthermore, participants contributed a dried blood spot sample, collected via finger prick. To assess malnutrition, we measured height and weight, applying WHO criteria to determine rates of underweight, wasting, and stunting. The assessment of immunity to poliovirus types 1, 2, and 3 through the detection of neutralizing antibodies was carried out at the CDC in Atlanta, USA.

Results

Of the study population, we found 24.7% underweight, 54.8% stunted, and 15.4% wasted. With IC95%, underweight (OR=1.50; [1.11-2.03]), and the non-administration of vitamin A (OR=1.96; [1.52-2.54]) were significantly associated with seronegativity to polioserotype 1. Underweight (OR=1.64; [1.20-2.24]) and the non-administration of vitamin A (OR=1.55; [1.20-2.01]) were significantly associated with seronegativity to polioserotype 2. Underweight (OR=1.50; [1.11-2.03]), and the non-administration of vitamin A (OR=1.80. [1.38-2.35]) were significantly associated with seronegativity to polioserotype 3. Underweight (OR=1.68; IC95% [1.10-2.57]) and the non-administration of vitamin A (OR=1.82; IC95% [1.30-2.55]) were significantly associated with seronegativity to all polioserotypes.

Conclusion

This study reveals a significant association between underweight and polioseronegativity in children. In order to reduce vaccine failures in high-risk areas, an integrated approach by vaccination and nutrition programs should be adopted.

Estimating population immunity to poliovirus in Lebanon: Results from a seroprevalence survey, 2016

INTRODUCTION

Circulation of poliovirus in neighboring countries and mass population movement places Lebanon at risk of polio and other vaccine-preventable disease outbreaks. Determining population immunity levels is essential for guiding program planning and implementation of targeted supplementary immunization activities (SIAs) in governorates and subpopulations with low seroprevalence.

METHODS

A cross-sectional multi-stage cluster survey was conducted during February-December 2016 in all six governorates of Lebanon adapted from the World Health Organization (WHO) recommended Expanded Progamme on Immunization (EPI) methodology. Sera from selected children aged 12-59 months were tested for poliovirus neutralizing antibodies.

RESULTS

Of 2,164 children recruited in this study, 1,893 provided sufficient quantity of serum samples for laboratory testing. Seroprevalence for all three poliovirus serotypes was greater than 90% in all six governorates. Poliovirus vaccine coverage with three or more doses, based on vaccination cards or parental recall, ranged between 54.1% for children aged 36-47 months in the North and 83.5% for children aged 48-59 months in Beirut.

CONCLUSION

Immunity to polioviruses was high in Lebanon in 2016 following a series of supplementary immunization activities. It is essential to continue strategies that increase vaccination coverage in order to sustain the considerably high immunity levels and prevent reintroduction and transmission of poliovirus. Educating caregivers and training health care workers on the standardized usage of home-based vaccination records is needed to guarantee the accuracy of records on children's vaccination status.

Poliovirus neutralizing antibody levels among individuals in three regions of Ghana

Introduction

Ghana was declared polio-free in 2015 after the last polio case in 2008. We determined the poliovirus neutralizing antibody levels among individuals to identify possible immunity gaps.

Methods

A cross-sectional, hospital-based study was undertaken in Northern, Ashanti and Greater Accra regions of Ghana. Individuals referred for haematology at the teaching hospitals' laboratories were invited to participate in our study. Neutralizing-antibody titers to poliovirus serotypes 1,2 & 3 were assayed by WHO-standards. Antibody titers of ≥8 were considered protective. Bivariate and multivariate analyses were conducted on subject characteristics to assess potential factors for failure to seroconvert. P-values < 0.05 were considered statistically significant.

Results

Poliovirus (PV) neutralizing-antibody serotypes 1, 2 and 3 were detected in 86.0% (264/307), 84% (258/307) and 75% (230/307) of samples respectively. 60.1% (185/307) were seropositive for the three poliovirus serotypes. Neutralizing poliovirus antibodies for PV1 and PV2 were higher than for PV3. Seroprevalence of poliovirus-neutralizing antibodies among males (PV1=51.9%, PV2= 51.6% and PV3= 52.6%) were higher than in females. Seroprevalence rates of poliovirus-neutralizing antibodies (PV1, PV2, and PV3) were highest in the Northern region (90%, 81%, and 77%). Poliovirus neutralizing-antibodies (PV1and PV2) decreased with age [p< 0.001]. Low seroprevalence of poliovirus-neutralizing antibodies was significantly associated with low school attendance of mothers (p<0.001).

Conclusion

Our study population has some protection from polio. However, immunity appears to be lower with a higher age or low Mother's education. This may suggest the need for young-adult booster-dose to minimize the risk of wild poliovirus infection.

Funding

WHO Country Office Ghana.

Poliovirus antibody levels and lameness among individuals in three regions of Ghana

Introduction: Ghana recorded the last case of poliomyelitis caused by wild poliovirus in 2008 and the country was declared polio-free in 2015. Polio-neutralizing-antibody levels in the population of three geographically representative regions of Ghana was determined, to identify possible immunity gaps.

Methods: Cross-sectional, hospital (1–70 years old) and school (primary, 1–15 years old)-based studies were undertaken in three regions in 2016. Individuals who visited the three teaching hospitals of the regions and were referred for haematology investigations were invited to participate in our study. Neutralizing-antibody titers to polio serotypes P1, P2, and P3 were assayed by WHO-standards. Antibody titers of ≥8 were considered protective. In the school lameness survey, clinical and epidemiological data were obtained from parents and their lamed children. Bivariate and multivariate analyses were conducted on subject characteristics, to assess potential factors for failure to seroconvert. P-values < 0.05 were considered statistically significant.

Results: Neutralizing-antibodies against poliovirus types 1, 2 and 3 were detected in 86% (264/307), 84% (258/307) and 75% (230/307) of the samples, respectively. Overall, 60.1% (185/307) were seropositive for the three polio serotypes and 2.9% (9/307) were seronegative. Polio neutralizing-antibodies (P1and P2) decreased with age (p < .001). Low seroprevalence of polio-neutralizing-antibodies was significantly associated with low school attendance of mothers (p < .001). Prevalence of residual paralysis was <1.0/1,000 among the school children.

Conclusion: Our study population is moderately protected against the three poliovirus serotypes. However, immunity appears to be lower with a higher age and low mother’s education. This may suggest the need for young-adult booster-dose to minimize the risk of wild poliovirus infection.

Trends in Poliovirus Seroprevalence in Kano State, Northern Nigeria

Background

Kano state has been a protracted reservoir of poliovirus in Nigeria. Immunity trends have been monitored through seroprevalence surveys since 2011. The survey in 2015 was, in addition, intended to assess the impact of use of inactivated poliovirus vaccine (IPV).

Methods

It was a health facility based seroprevalence survey. Eligible children aged 6-9, 12-15 and 19-22 months of age brought to the paediatrics outpatient department of Murtala Mohammad Specialist Hospital between 19 October and 6 November 2015, were screened for eligibility. Eligible children were enrolled after parental consent, history taken, physical examination conducted, and a blood sample collected to test for neutralizing antibody titres against the three poliovirus serotypes.

Results

Overall, 365 results were available in the three age groups. In the 6-9-month-old age group, the seroprevalence was 73% (95% confidence interval [CI] 64-80%), 83% (95% CI 75-88%), and 66% (95% CI 57-73%) for serotypes 1, 2, and 3, respectively. In the 12-15- and 19-22-month-old age groups, seroprevalence was higher but still remained <90% across serotypes. Seroprevalence to serotypes 1 and 3 in 2015 was similar to 2014; however, for serotype 2 there was a significant improvement. IPV received in supplemental immunization activities was found to be a significant predictor of seropositivity among 6-9-month-old infants for serotypes 1 and 2.

Conclusions

Seroprevalence for serotypes 1 and 3 remains low (<80%) in 6-9-month-olds. This poses a significant risk for poliovirus spread if reintroduced into the population. Efforts to strengthen immunization coverage are imperative to secure and sustain high population immunity.

Survey of poliovirus antibodies in Borno and Yobe States, North-Eastern Nigeria

BACKGROUND

Nigeria remains one of only three polio-endemic countries in the world. In 2016, after an absence of 2 years, wild poliovirus serotype 1 was again detected in North-Eastern Nigeria. To better guide programmatic action, we assessed the immunity status of infants and children in Borno and Yobe states, and evaluated the impact of recently introduced inactivated poliovirus vaccine (IPV) on antibody seroprevalence.

METHODS AND FINDINGS

We conducted a facility-based study of seroprevalence to poliovirus serotypes 1, 2 and 3 among health-seeking patients in two sites each of Borno and Yobe States. Enrolment was conducted amongst children 6-9 and 36-47 months of age attending the paediatrics outpatient department of the selected hospitals in the two states between 11 January and 5 February 2016. Detailed demographic and immunization history of the child was taken and an assessment of the child's health and nutritional state was conducted via physical examination. Blood was collected to test for levels of neutralizing antibody titres against the three poliovirus serotypes. The seroprevalence in the two age groups, potential determinants of seropositivity and the impact of one dose of IPV on humoral immunity were assessed. A total of 583 subjects were enrolled and provided sufficient quantities of serum for testing. Among 6-9-month-old infants, the seroprevalence was 81% (74-87%), 86% (79-91%), and 72% (65-79%) in Borno State, and 75% (67-81%), 74% (66-81%) and 69% (61-76%) in Yobe States, for serotypes-1, 2 and 3, respectively. Among children aged 36-47 months, the seroprevalence was >90% in both states for all three serotypes, with the exception of type 3 seroprevalence in Borno [87% (80-91%)]. Median reciprocal anti-polio neutralizing antibody titers were consistently >900 for serotypes 1 and 2 across age groups and states; with lower estimates for serotype 3, particularly in Borno. IPV received in routine immunization was found to be a significant determinant of seropositivity and anti-polio neutralizing antibodies among 6-9-month-old infants for serotypes 1 and 3, but demonstrated a non-significant positive association for serotype 2. Children receiving IPV through SIAs demonstrated significantly higher anti-polio neutralizing antibodies for serotypes 1 and 3.

CONCLUSIONS

The seroprevalence to poliovirus remains suboptimal in both Borno and Yobe States in Nigeria. The low seroprevalence facilitated the continued transmission of both wild serotype 1 and serotype 2 circulating vaccine-derived poliovirus detected in Borno State in 2016. Further efforts are necessary to improve the immunity status of these populations to ensure sufficient population immunity to interrupt transmission.

Poliovirus seroprevalence before and after interruption of poliovirus transmission in Kano State, Nigeria

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Polio seroprevalence surveys help measure progress towards polio eradication.

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Nigeria program conducted multiple seroprevalence surveys in northern states.

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This article covers seroprevalence survey in Kano Nigeria in 2013 and 2014.

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Data represents levels before and after the interruption of poliovirus transmission.

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Significant improvement in seroprevalence in 2014 over 2013, but gaps continue.

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Good participation even by vaccine refusers in this health facility based project.

Introduction

In September 2015, Nigeria was removed from the list of polio-endemic countries after more than 12 months had passed since the detection of last wild poliovirus case in the country on 24 July 2014. We are presenting here a report of two polio seroprevalence surveys conducted in September 2013 and October 2014, respectively, in the Kano state of northern Nigeria.

Methods

Health facility based seroprevalence surveys were undertaken at Murtala Mohammad Specialist Hospital, Kano. Parents or guardians of children aged 6–9 months, 36–47 months, 5–9 years and 10–14 years in 2013 and 6–9 months and 19–22 months (corresponding to 6–9 months range at the time of 2013 survey) in 2014 presenting to the outpatient department, were approached for participation, screened for eligibility and asked to provide informed consent. A questionnaire was administered and a blood sample collected for polio neutralization assay.

Results

Among subjects aged 6–9 months in the 2013 survey, seroprevalence was 58% (95% confidence interval [CI] 51–66%) to poliovirus type 1, 42% (95% CI 34–50%) to poliovirus type 2, and 52% (95% CI 44–60%) to poliovirus type 3. Among children 36–47 months and older, seroprevalence was 85% or higher for all three serotypes. In 2014, seroprevalence in 6–9 month infants was 72% (95% CI 65–79%) for type 1, 59% (95% CI 52–66%) for type 2, and 65% (95% CI 57–72%) for type 3 and in 19–22 months, 80% (95% CI 74–85%), 57% (49–63%) and 78% (71–83%) respectively. Seroprevalence was positively associated with history of increasing oral poliovirus vaccine doses.

Conclusions

There was significant improvement in seroprevalence in 2014 over the 2013 levels indicating a positive impact of recent programmatic interventions. However the continued low seroprevalence in 6–9 month age is a concern and calls for improved immunization efforts to sustain the polio-free Nigeria.

Factors determining anti-poliovirus type 3 antibodies among orally immunised Indian infants

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88.1% of 8454 children screened had protective antibodies to poliovirus serotype 3.

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The number of tOPV doses received was the main determinant of seroprevalence.

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Age, gender, residence and number of tOPV doses are associated with seroprevalence.

Background

Among the three poliovirus serotypes, the lowest responses after vaccination with trivalent oral polio vaccine (tOPV) are to serotype 3. Although improvements in routine immunisation and supplementary immunisation activities have greatly increased vaccine coverage, there are limited data on antibody prevalence in Indian infants.

Methods

Children aged 5–11 months with a history of not having received inactivated polio vaccine were screened for serum antibodies to poliovirus serotype 3 (PV3) by a micro-neutralisation assay according to a modified World Health Organization (WHO) protocol. Limited demographic information was collected to assess risk-factors for a lack of protective antibodies. Student’s t-test, logistic regression and multilevel logistic regression (MLR) model were used to estimate model parameters.

Results

Of 8454 children screened at a mean age of 8.3 (standard deviation [SD]-1.8) months, 88.1% (95% confidence interval (CI): 87.4–88.8) had protective antibodies to PV3. The number of tOPV doses received was the main determinant of seroprevalence; the maximum likelihood estimate yields a 37.7% (95% CI: 36.2–38.3) increase in seroprevalence per dose of tOPV. In multivariable logistic regression analysis increasing age, male sex, and urban residence were also independently associated with seropositivity (Odds Ratios (OR): 1.17 (95% CI: 1.12–1.23) per month of age, 1.27 (1.11–1.46) and 1.24 (1.05–1.45) respectively).

Conclusion

Seroprevalence of antibodies to PV3 is associated with age, gender and place of residence, in addition to the number of tOPV doses received. Ensuring high coverage and monitoring of response are essential as long as oral vaccines are used in polio eradication.

Seroepidemiology: an underused tool for designing and monitoring vaccination programmes in low- and middle-income countries

Seroepidemiology, the use of data on the prevalence of bio-markers of infection or vaccination, is a potentially powerful tool to understand the epidemiology of infection before vaccination and to monitor the effectiveness of vaccination programmes. Global and national burden of disease estimates for hepatitis B and rubella are based almost exclusively on serological data. Seroepidemiology has helped in the design of measles, poliomyelitis and rubella elimination programmes, by informing estimates of the required population immunity thresholds for elimination. It contributes to monitoring of these programmes by identifying population immunity gaps and evaluating the effectiveness of vaccination campaigns. Seroepidemiological data have also helped to identify contributing factors to resurgences of diphtheria, Haemophilus Influenzae type B and pertussis. When there is no confounding by antibodies induced by natural infection (as is the case for tetanus and hepatitis B vaccines), seroprevalence data provide a composite picture of vaccination coverage and effectiveness, although they cannot reliably indicate the number of doses of vaccine received. Despite these potential uses, technological, time and cost constraints have limited the widespread application of this tool in low-income countries. The use of venous blood samples makes it difficult to obtain high participation rates in surveys, but the performance of assays based on less invasive samples such as dried blood spots or oral fluid has varied greatly. Waning antibody levels after vaccination may mean that seroprevalence underestimates immunity. This, together with variation in assay sensitivity and specificity and the common need to take account of antibody induced by natural infection, means that relatively sophisticated statistical analysis of data is required. Nonetheless, advances in assays on minimally invasive samples may enhance the feasibility of including serology in large survey programmes in low-income countries. In this paper, we review the potential uses of seroepidemiology to improve vaccination policymaking and programme monitoring and discuss what is needed to broaden the use of this tool in low- and middle-income countries.

Role of Serial Polio Seroprevalence Studies in Guiding Implementation of the Polio Eradication Initiative in Kano, Nigeria: 2011-2014

BACKGROUND

Nigeria was one of 3 polio-endemic countries before it was de-listed in September 2015 by the World Health Organization, following interruption of transmission of the poliovirus. During 2011-2014, Nigeria conducted serial polio seroprevalence surveys (SPS) in Kano Metropolitan Area, comprising 8 local government areas (LGAs) in Kano that is considered very high risk (VHR) for polio, to monitor performance of the polio eradication program and guide the program in the adoption of innovative strategies.

METHODS

Study subjects who resided in any of the 8 local government areas of Kano Metropolitan Area and satisfied age criteria were recruited from patients at Murtala Mohammed Specialist Hospital (Kano) for 3 seroprevalence surveys. The same methods were used to conduct each survey.

RESULTS

The 2011 study showed seroprevalence values of 81%, 75%, and 73% for poliovirus types 1, 2, and 3, respectively, among infants aged 6-9 months age. Among children aged 36-47 months, seroprevalence values were greater (91%, 87%, and 85% for poliovirus types 1, 2, and 3, respectively).In 2013, the results showed that the seroprevalence was unexpectedly low among infants aged 6-9 months, remained high among children aged 36-47 months, and increased minimally among children aged 5-9 years and those aged 10-14 years. The baseline seroprevalence among infants aged 6-9 months in 2014 was better than that in 2013.

CONCLUSIONS

The results from the polio seroprevalence surveys conducted in Kano Metropolitan Area in 2011, 2013, and 2014 served to assess the trends in immunity and program performance, as well as to guide the program, leading to various interventions being implemented with good effect, as evidenced by the reduction of poliovirus circulation in Kano.

Seroprevalence rate of Poliovirus antibodies among the Healthy and Protein Energy Malnutrition children

Objective:

To study the association between Protein energy malnutrition and polio-specific immunoglobulin G antibodies production among children in Gadap Town Karachi, Pakistan.

Methods:

Comparative cross sectional survey conducted at fixed EPI center and Pediatric OPD of a tertiary care hospital Karachi. Children were selected by convenient sampling method during the period from 17 March to 17 May 2013. It was ensured that they must have received more than seven oral polio vaccine doses as eligibility criteria for the study. A total of 170 blood samples were collected and tested for the presence of polio-specific IgG antibodies using Poliomyelitis IgG ELISA Test Kit produced.

Results:

Statistically significant relation was found between PEM and IgG antibodies production OR (P = 0.000). Overall Seroprevalence rate among the study population was 98.8%, PEM group 97.6% and healthy group 100%.

Conclusion:

The study demonstrated that there is a need to focus on the protein energy malnutrition among the children as an immunization strategy for the 100% seroprevalence rate in all population against polio in Pakistan.

Immunogenicity of poliovirus vaccines in chronically malnourished infants: a randomized controlled trial in Pakistan

Reaching high population immunity against polioviruses (PV) is essential to achieving global polio eradication. Efficacy of oral poliovirus vaccine (OPV) varies and is lower among children living in tropical areas with impoverished environments. Malnutrition found as a risk factor for lower serological protection against PV. We compared whether inactivated polio vaccine (IPV) can be used to rapidly close the immunity gap among chronically malnourished (stunted) infants in Pakistan who will not be eligible for the 14 week IPV dose in routine EPI schedule. A phase 3, multicenter 4-arm randomized controlled trial conducted at five Primary Health Care (PHC) centers in Karachi, Pakistan. Infants, 9–12 months were stratified by length for age Z score into chronically malnourished and normally nourished. Infants were randomized to receive one dose of either bivalent OPV (bOPV) alone or bOPV + IPV. Baseline seroprevalence of PV antibodies and serum immune response to study vaccine dose were assessed by neutralization assay. Vaccine PV shedding in stool was evaluated 7 days after a bOPV challenge dose. Sera and stool were analyzed from 852/928 (92%) enrolled children. At baseline, the seroprevalence was 85.6% (n = 386), 73.6% (n = 332), and 70.7% (n = 319) in malnourished children against PV types 1, 2 and 3 respectively; and 94.1% (n = 448), 87.0% (n = 441) and 83.6% (n = 397) in the normally nourished group (p < 0.05). Children had previously received 9–10 doses of bOPV (80%) or tOPV (20%). One dose of IPV + bOPV given to malnourished children increased their serological protection (PV1, n = 201, 97.6%; PV2, n = 198, 96.1% and PV3, n = 189, 91.7%) to parity with normally nourished children who had not received IPV (p = <0.001). Seroconversion and boosting for all three serotypes was significantly more frequent in children who received IPV + bOPV than in those with bOPV only (p < 0.001) in both strata. Shedding of polioviruses in stool did not differ between study groups and ranged from 2.4% (n = 5) to 7.1% (n = 15). In malnourished children the shedding was reduced after bOPV + IPV compared to bOPV only.

Chronically malnourished infants were more likely to be unprotected against polioviruses than normal infants. bOPV + IPV helped close the immunity gap better than bOPV alone.

Assessing population immunity in a persistently high-risk area for wild poliovirus transmission in India: a serological study in Moradabad, Western Uttar Pradesh

BACKGROUND

Moradabad district in Uttar Pradesh reported the highest number of paralytic polio cases in India during 2001-2007. We conducted a study in Moradabad in 2007 to assess seroprevalence against poliovirus types 1, 2, and 3 in children 6-12 and 36-59 months of age to guide future strategies to interrupt wild poliovirus transmission in high-risk areas.

METHODS

Children attending 10 health facilities for minor illnesses who met criteria for study inclusion were eligible for enrollment. We recorded vaccination history, weight, and length and tested sera for neutralizing antibodies to poliovirus types 1, 2, and 3.

RESULTS

Poliovirus type 1, 2, and 3 seroprevalences were 88% (95% confidence interval [CI], 84%-91%), 70% (95% CI, 66%-75%), and 75% (95% CI, 71%-79%), respectively, among 467 in the younger age group (n=467), compared with 100% (95% CI, 99%-100%), 97% (95% CI, 95%-98%), and 93% (91%-95%), respectively, among 447 children in the older age group (P<.001 for all serotypes).

CONCLUSIONS

This seroprevalence study provided extremely useful information that was used by the program in India to guide immunization policies, such as optimizing the use of different OPV formulations in vaccination campaigns and strengthening routine immunization services. Similar surveys in populations at risk should be performed at regular intervals in countries where the risk of persistence or spread of indigenous or imported wild poliovirus is high.

Survey of poliovirus antibodies in Kano, Northern Nigeria

INTRODUCTION

In 1988, the World Health Assembly resolved to eradicate poliomyelitis. Since then, much progress towards this goal has been made, but three countries including Nigeria remain polio-endemic as of end 2012. To assess the immunity level against poliomyelitis in young children in Northern Nigeria, we conducted a seroprevalence survey in the Kano Metropolitan Area (KMA) in May 2011.

METHODS

Parents or guardians of infants aged 6-9months or children aged 36-47months presenting to the outpatient department of Murtala Mohammad Specialist Hospital were approached for participation, screened for eligibility and were asked to provide informed consent. After that, a questionnaire was administered and blood was collected for neutralization assay.

RESULTS

A total of 327 subjects were enrolled. Of these, 313 (96%) met the study requirements and were analyzed (161 [51%] aged 6-9months and 152 [49%] aged 36-47months). Among subjects aged 6-9months, seroprevalence was 81% (95% confidence interval [CI] 75-87%) to poliovirus type 1, 76% (95% CI 68-81%) to poliovirus type 2, and 73% (95% CI 67-80%) to poliovirus type 3. Among subjects aged 36-47months, the seroprevalence was 91% (95% CI 86-95%) to poliovirus type 1, 87% (95% CI 82-92%) for poliovirus type 2, and 86% (95% CI 80-91%) to poliovirus type 3. Seroprevalence was associated with history of oral poliovirus vaccine (OPV) doses, maternal education and gender.

CONCLUSIONS

Seroprevalence is lower than required levels for poliovirus interruption in the KMA. Persistence of immunity gaps in the 36-47months group is a big concern. Since higher number of vaccine doses is associated with higher seroprevalence, it implies that failure-to-vaccinate and not vaccine failure accounts for the suboptimal seroprevalence. Intensified efforts are necessary to administer polio vaccines to all target children and surpass the threshold levels for herd immunity.

Seroprevalence of poliovirus antibodies amongst children in Zaria, Northern Nigeria

BACKGROUND

Poliomyelitis is endemic in Northern Nigeria where there is continuous transmission of wild poliovirus 1 and 3 (WPV1 and 3) and circulating vaccine derived poliovirus 2 (cVDPV2) resulting in a high number of cases of children with acute flaccid paralysis. The seroprevalence of antibodies to polio serotypes which can be used to assess the immune status of children and the effectiveness of the vaccine against poliomyelitis is unknown, despite its endemicity in this part of the world.

OBJECTIVE

This study aimed to determine the seroprevalence of poliovirus antibodies in children aged 1-10 years in Zaria, Northern Nigeria.

METHODS

A descriptive, cross sectional, community based study was undertaken in Zaria, North Western Nigeria between 2008 and 2009. Two hundred and sixty-four (264) children aged 1-10 years were enrolled from two local government in Zaria by multistage random sampling method. Demographic data and polio immunisation history were retrieved from parents and caregivers by an interviewer administered questionnaire. Neutralising antibody titres to polioserotypes 1, 2 and 3 were assayed according to the WHO Manual for the virological investigation of polio. Antibody titres ≥ 1:8 were considered positive.

RESULTS

The mean age of the 264 children studied was 6.25 years. Fifty-five percent of the children were protected against the three polioserotypes, while 86.4%, 76.1% and 77.3% of children had neutralising antibodies to P1, P2 and P3 polioserotypes respectively. 5 (1.9%) of the children had no antibodies to all the three polioserotypes. Polio antibody seropositivity was significantly associated with higher socioeconomic status and immunisation was the single most important determinant of seropositivity to poliovirus serotypes.

CONCLUSION

Seroprevalence to poliovirus serotypes, though higher than values found in previous studies done in Nigeria, was lower compared to findings in the developed world. The use of more immunogenic vaccines and the balanced use of OPV formulations in SIAs, with further improvements in programme quality could provide the necessary immune booster to make polio eradication in Nigeria a reality.

Testing clinical surveillance of acute flaccid paralysis in Egypt post-eradication of poliomyelitis

OBJECTIVE

To assess the knowledge of polio detection and notification by front-line clinicians in Egypt.

METHODS

This study examines clinicians' knowledge and awareness of polio detection and notification using a multiple-choice questionnaire (maximum score=43) in three large health care centres in central Cairo (n=52).

RESULTS

The results reveal a significant variation of knowledge amongst doctors, with junior and senior house officers scoring an average of 30.6 (95% CI: 29.5-31.7), specialist registrars and consultant paediatricians 30.3 (CI 28.9-31.7), and public health doctors 35.4 (CI 32.9-36.8). Mean total scores of public health doctors were significantly higher than those of other clinicians. Senior paediatricians performed no better than newly qualified doctors.

CONCLUSIONS

The results suggest that there is a need for more clinical teaching and training amongst junior doctors as well as senior clinicians and consultants. Appropriate knowledge of diagnosing AFP and of the correct protocol amongst clinicians is essential to maintain the high quality of the WHO programme in Egypt.