National immunisation days for polio eradication in Uganda: did immunisation cards increase coverage?

OBJECTIVE

To analyse the effect of cards and of vitamin A supplementation on coverage for National Immunisation Days (NIDs).

DESIGN

A retrospective ecological study.

SETTING

A countrywide NIDs coverage before and after introduction of the NIDs cards and vitamin A supplementation in all districts of Uganda.

METHODS

NIDs for polio eradication commenced in Uganda in 1996. Two rounds, one month apart are implemented yearly. During the second round of 1998 NIDs, cards were introduced nationally and vitamin supplementation was introduced in 24 of the 45 districts. We compared NIDs coverage before and after NIDs cards and NIDs coverage in districts that implemented vitamin A to those that did not.

RESULTS

After introduction of NIDs cards, the national coverage rose from 97.7% to 106.9%, an increase of 9.2%. In those districts that implemented vitamin A supplementation, the NIDs coverage rose from 100.1% to 111.5%, an increase of 10.4%. In those districts that did not implement vitamin A, the NIDs coverage rose by 6.7% from 94.5% to 102.2%. Before the introduction of cards and vitamin A in 1996 and 1997, the NIDs coverage was between 92-96%.

CONCLUSION

NIDs cards and vitamin A supplementation could have increased the NIDs national coverage.

Stopping poliovirus vaccination after eradication: issues and challenges

Since 1988 reported polio cases worldwide have declined by about 85% and the number of known or suspected polioendemic countries has decreased from over 120 to less than 50. With eradication of poliomyelitis approaching, issues potentially affecting when and how vaccination against poliovirus can be stopped become extremely important. Because of the potential risks and benefits inherent in such a decision, the best available science, a risk-benefit analysis, contingency plans, a stock pile of poliovirus vaccines, and the endorsement by the global policy-making committees will all be needed before vaccination can be discontinued. The scientific basis for stopping polio immunization has been reviewed by WHO. This Round Table article summarizes the current state of knowledge, provides an update on the processes and timelines for certification, containment, and stopping vaccination, and highlights some of the unanswered scientific questions that will be addressed by further research. These include whether transmission of vaccine-derived poliovirus strains could be sustained so that poliomyelitis could re-emerge in a future unvaccinated population and whether prolonged excretion of vaccine-derived poliovirus from individuals with immune deficiencies could be a mechanism through which this could occur.

Excluding polio in areas of inadequate surveillance in the final stages of eradication in China

In 1996, China adopted a virological classification of acute flaccid paralysis (AFP) cases for its surveillance system. Only AFP cases with wild poliovirus in stool specimens are confirmed as polio. Cases with adequate stool specimens that are negative for wild poliovirus are not counted. This paper describes a methodology to rule out poliomyelitis in AFP cases with inadequate stool specimens. National surveillance data were analysed using dot maps to detect clusters of AFP cases with high-risk factors for poliomyelitis. The surveillance system and vaccine coverage were assessed during field investigations. Four clusters of AFP cases were identified, but no poliomyelitis cases. Programmatic failures in the identified high-risk areas included low vaccination rates, poor stool specimen collection and inadequate AFP surveillance. Programme strategies were implemented to correct the identified failures. Use of this methodology provides strong evidence consistent with the absence of wild poliovirus in China.

Eradication of poliomyelitis in countries affected by conflict

The global initiative to eradicate poliomyelitis is focusing on a small number of countries in Africa (Angola, Democratic Republic of the Congo, Liberia, Sierra Leone, Somalia, Sudan) and Asia (Afghanistan, Tajikistan), where progress has been hindered by armed conflict. In these countries the disintegration of health systems and difficulties of access are major obstacles to the immunization and surveillance strategies necessary for polio eradication. In such circumstances, eradication requires special endeavours, such as the negotiation of ceasefires and truces and the winning of increased direct involvement by communities. Transmission of poliovirus was interrupted during conflicts in Cambodia, Colombia, El Salvador, Peru, the Philippines, and Sri Lanka. Efforts to achieve eradication in areas of conflict have led to extra health benefits: equity in access to immunization, brought about because every child has to be reached; the revitalization and strengthening of routine immunization services through additional externally provided resources; and the establishment of disease surveillance systems. The goal of polio eradication by the end of 2000 remains attainable if supplementary immunization and surveillance can be accelerated in countries affected by conflict.

The global poliomyelitis eradication initiative: progress and challenges

In 1988, The World Health Assembly committed WHO and its member states to the goal of poliomyelitis eradication by the year 2000. Global progress in implementation of strategies include routine and supplementary immunisation, AFP surveillance strategy and mopping up. Progress made in global polio eradication within 10 years has been dramatic. Challenges consist of tailoring and fine tuning strategies and sustaining adequate levels of findings. Although the intensified effort will increase needed resources in the short term, it will save costs in the long term.

Disease eradication as a public health strategy: a case study of poliomyelitis eradication

Disease eradication as a public health strategy was discussed at international meetings in 1997 and 1998. In this article, the ongoing poliomyelitis eradication initiative is examined using the criteria for evaluating candidate diseases for eradication proposed at these meetings, which covered costs and benefits, biological determinants of eradicability (technical feasibility) and societal and political considerations (operational feasibility). The benefits of poliomyelitis eradication are shown to include a substantial investment in health services delivery, the elimination of a major cause of disability, and far-reaching intangible effects, such as establishment of a "culture of prevention". The costs are found to be financial and finite, despite some disturbances to the delivery of other health services. The "technical" feasibility of poliomyelitis eradication is seen in the absence of a non-human reservoir and the presence of both an effective intervention and delivery strategy (oral poliovirus vaccine and national immunization days) and a sensitive and specific diagnostic tool (viral culture of specimens from acute flaccid paralysis cases). The certification of poliomyelitis eradication in the Americas in 1994 and interruption of endemic transmission in the Western Pacific since March 1997 confirm the operational feasibility of this goal. When the humanitarian, economic and consequent benefits of this initiative are measured against the costs, a strong argument is made for eradication as a valuable disease control strategy.

Poliomyelitis surveillance: the model used in India for polio eradication

Poliomyelitis surveillance in India previously involved the passive reporting of clinically suspected cases. The capacity for detecting the disease was limited because there was no surveillance of acute flaccid paralysis (AFP). In October 1997, 59 specially trained Surveillance Medical Officers were deployed throughout the country to establish active AFP surveillance; 11,533 units were created to report weekly on the occurrence of AFP cases at the district, state and national levels; timely case investigation and the collection of stool specimens from AFP cases was undertaken; linkages were made to support the polio laboratory network; and extensive training of government counterparts of the Surveillance Medical Officers was conducted. Data reported at the national level are analysed and distributed weekly. Annualized rates of non-polio AFP increased from 0.22 per 100,000 children aged under 15 years in 1997 to 1.39 per 100,000 in 1999. The proportion of cases with two adequate stools collected within two weeks of the onset of paralysis increased from 34% in 1997 to 68% in 1999. The number of polio cases associated with the isolation of wild poliovirus decreased from 211 in the first quarter of 1998 to 77 in the first quarter of 1999. Widespread transmission of wild poliovirus types 1 and 3 persists throughout the country; type 2 occurs only in Bihar and Uttar Pradesh. In order to achieve polio eradication in India during 2000, extra national immunization days and house-to-house mopping-up rounds should be organized.

Transmissibility and persistence of oral polio vaccine viruses: implications for the global poliomyelitis eradication initiative

The global poliomyelitis eradication initiative has been a tremendous success, with current evidence suggesting that wild poliovirus will cease to circulate anywhere in the world soon after the year 2000. As the goal of wild poliovirus eradication is approached, concern has been raised about the potential for persistent transmission of oral polio vaccine (OPV) viruses, as these viruses are known to revert toward wild-type neurovirulence. This paper has been extracted from a document prepared for the World Health Organization on the implications of OPV transmissibility for the strategy of stopping OPV vaccination after global eradication of wild polioviruses. The authors review the empirical evidence on OPV transmissibility available from household and community transmission studies and from mass-vaccination experiences. They then consider theoretical measures of transmissibility and persistence for wild and OPV viruses (secondary attack rate, basic reproduction number, and critical populations' size), to assess whether transmissibility of OPV viruses is sufficient to allow persistence of these viruses after cessation of vaccination. The findings indicate that OPV viruses could persist under various plausible circumstances, and that this potential should be a major consideration when planning the cessation of OPV vaccination.

Awareness about a national immunization day programme in the Sunsari district of Nepal

The initiative to eradicate poliomyelitis globally by the year 2000 was launched at the Forty-first World Health Assembly in May 1988, when all WHO Member States were challenged to help eradicate poliomyelitis from the world, a gift to the children of the twenty-first century. In Nepal, 100-250 children per year become disabled due to poliomyelitis. The government of Nepal is determined to eradicate the disease from the country by the year 2000 through the National Immunization Day (NID) Programme. Since 1996, about 3.3 million children under 5 years of age have been immunized each year in Nepal. In the present study, we analysed the impact of the campaign in the Sunsari district of Nepal. The study was carried out during the first NID (6 December 1996) to evaluate the local population's awareness of the programme and the impact of the media on such awareness. A total of 843 respondents were interviewed, 39% of whom were illiterate. Two important aspects of the mass campaign (whether a child previously immunized should be immunized again in the NID, and whether children should be brought to the next NID) were clearly understood by the majority of the people (93.1% and 98.8% of the respondents, respectively), although only a small proportion (24.4%) of individuals understood the purpose of the programme. Radio was the single most effective means of providing information, education, and communication about NIDs. The encouraging response, especially from a poor, illiterate rural population, augurs well for the goal of eradicating poliomyelitis from the world.

Oral iodine supplementation does not reduce neutralizing antibody responses to oral poliovirus vaccine

Iodine deficiency is a major cause of impaired mental development, goitre, and cretinism in many parts of the world. Because existing immunization programmes can be used to deliver oral iodized oil (OIO) to infants at risk, it was important to know whether OIO could adversely affect the antibody response to vaccines, such as trivalent oral poliovirus vaccine (OPV). A randomized, double-blind, placebo-controlled clinical trial was conducted in Subang, West Java, Indonesia, in which 617 eight-week-old infants received either OIO or a placebo (poppy-seed oil) during a routine visit for their first dose of OPV as part of the Expanded Programme on Immunization (EPI). The infants received two boosters of OPV at 4-week intervals after the first dose, and were followed up when 6 months old. Neutralizing antibody titres to poliovirus serotypes 1, 2, and 3 were compared in serum samples that were taken from 478 of these infants just before the first dose of OPV and at 6 months. It was found that oral iodized oil did not reduce the antibody responses to any of the three serotypes of OPV. These results indicate that oral iodine may safely be delivered to infants at the same time as oral poliovirus vaccine according to current EPI immunization schedules.

Cluster survey evaluation of coverage and risk factors for failure to be immunized during the 1995 National Immunization Days in Egypt

BACKGROUND

In 1995, Egypt continued to experience endemic wild poliovirus transmission despite achieving high routine immunization coverage with at least three doses of oral poliovirus vaccine (OPV3) and implementing National Immunization Days (NIDs) annually for several years.

METHODS

Parents of 4188 children in 3216 households throughout Egypt were surveyed after the second round of the 1995 NIDs.

RESULTS

Nationwide, 74% of children are estimated to have received both NID doses, 17% one NID dose, and 9% neither NID dose. Previously unimmunized (47%) or partially immunized (64%) children were less likely to receive two NID doses of OPV than were fully immunized children (76%) (P < 0.001). Other risk factors nationwide for failure to receive NID OPV included distance from residence to nearest NID site >10 minute walk (P < 0.001), not being informed about the NID at least one day in advance (P < 0.001), and residing in a household which does not watch television (P < 0.001). Based on these findings, subsequent NIDs in Egypt were modified to improve coverage, which has resulted in a marked decrease in the incidence of paralytic poliomyelitis in Egypt.

CONCLUSIONS

In selected situations, surveys can provide important information that is useful for planning future NIDs.

Sentinel surveillance on poliomyelitis and neonatal tetanus: a report

A 5 year sentinel surveillance (1989-93) of paralytic poliomyelitis and neonatal tetanus was undertaken at a rural Medical College Hospital at Burdwan, West Bengal. Poliomyelitis incidence showed an overall declining trend, which corroborated with the increased OPV coverage over the years. Incidence was more in males than females. Male:female ratio varied between 2.31:1 to 1.2:1. From 1989 to 1992, age-shift in poliomyelitis was observed when more cases were occurring above 1 year subjects. Cases were reported to be high during the months June to September every year. Incidence of neonatal tetanus (NNT) also showed a declining trend during the 5 year study period. A male preponderance was observed. NNT cases were more prevalent during the months between August and November. In an attempt for eradication of paralytic poliomyelitis and elimination of NNT, containment and other public health measures were undertaken a part of surveillance activities. The obstacles encountered in the surveillance system, as well as lacunae identified in undertaking appropriate health measures was discussed.

All hands against polio

The students and faculty of the Aga Khan University School of Nursing, working in collaboration with other groups and organizations, have made a considerable contribution to Pakistan's polio immunization programme in the area of District Council West and Malir, Karachi. Recommendations for improving the programme are presented on the basis of the experience gained.

Protecting the world's children: the story of WHO's immunization programme

Systematic immunization on a worldwide scale was not officially recognized as a practical possibility until 1974, when WHO launched its Expanded Programme on Immunization. Today, 80% of the world's children receive this form of protection against childhood diseases during their first year of life. Coverage can reach 90% by the year 2000, the effectiveness of the vaccines used is improving, and vaccines against additional diseases are being added to the programme.

Rehabilitation of the expanded programme on immunization in Sudan following a poliomyelitis outbreak

In 1993 a large outbreak of paralytic poliomyelitis occurred in Sudan as a result of an accumulation of large numbers of susceptible children that was accelerated by faltering immunization services. The extent of the outbreak led to the rapid rehabilitation of Sudan's Expanded Programme on Immunization (EPI); the government began financing vaccine purchase, operational aspects of EPI were decentralized, vaccine delivery was changed from a mobile to a fixed-site strategy, a solar cold chain network was installed, inservice training was resuscitated, and social mobilization was enhanced. National immunization days (NIDs) for poliomyelitis eradication were conducted throughout the country, including the southern states during a cease fire in areas of conflict. Measles immunization coverage was increased by offering measles vaccine during the second round of NIDs and subsequently through routine immunization services. Supplemental tetanus toxoid immunization of women of child-bearing age began in three provinces at high risk for neonatal tetanus. From 1994 to 1996 reported immunization coverage increased and the incidence of all EPI target diseases fell. Trends in coverage, disease incidence, financing, and the implementation of WHO-recommended disease-control strategies suggest that more sustainable immunization services have been re-established in Sudan.

Rare adverse events associated with oral poliovirus vaccine in Brazil

Oral poliovirus vaccine (OPV) developed by A. Sabin has been effectively used to control poliomyelitis in Brazil, and the last case with the isolation of a wild poliovirus strain occurred in March 1989. Although the vaccine controlled the circulation of wild strains and poliomyelitis cases associated with these strains were not detected during the last eight years, rare cases classified as vaccine-associated paralytic poliomyelitis (VAPP) have been detected. Molecular characterization studies of poliovirus strains isolated from VAPP cases and from healthy contacts have confirmed that the isolates are derived from the Sabin vaccine strains and also detected genomic modifications known or suspected to increase neurovirulence such as mutations and recombination. The molecular characterization of polioviruses isolated during the last eight years from paralysis cases classified as Guillain-Barré (GBS) syndrome and transverse myelitis (TM), and from facial paralysis (FP) cases also confirmed the vaccine origin of the strains and demonstrated mutations known to increase neurovirulence. Analysis of the epidemiologic data of these GBS, TM and FP cases demonstrated that in most of them the last OPV dose was given months or years before the onset of the disease and the isolation of the polioviruses. The temporal association between the isolation of these strains and the GBS, TM and FP suggested that the Sabin vaccine-derived poliovirus strains could also rarely trigger the diseases.