World Health Organization Expanded Research Articles

Missed opportunities for immunization among children 0 to 11 months of age that were attended to at debre tabor comprehensive specialized hospital, south gondar zone, Ethiopia.

The World Health Organization's Expanded Immunization Program was established in 1974 and aimed to provide vaccines to children all over the world. Since the inception of this program, numerous initiatives and campaigns have been launched, and millions of children around the world have been saved from death. Many vaccine-preventable diseases, however, remain prevalent in developing countries. This is because most of those countries have low immunization coverage for an unknown number of reasons. As a result, the goal of this study was to examine missed opportunities for immunization among children aged 0 to 11 months. A cross-sectional survey was carried out from May to August 2022. A structured questionnaire was used to collect data, and the sample was chosen using a simple random sampling technique. Before being entered into the Epidata and exported to the Statistical Package for Social Science for analysis, the data were checked for consistency and completeness. The statistical significance was determined using binary and multiple logistic regression analyses. The statistical level of significance was established at p ≤ 0.05. In this study, 49.1% of immunization opportunities were missed. Education status [AOR = 2.45, 95% CI = 2.14, 4.22], rural residence [AOR = 4.32, 95% CI = 3.11, 6.38], and perception of caretakers [AOR = 2.13, 95% CI = 1.89, 4.07] were associated with the missed opportunity of immunization. When compared to previous studies, the proportion of missed immunization opportunities was high in this study. The healthcare staff should be applying the multi-dose vial policy, which is recommended by the World Health Organization to increase the services. The doses for BCG and measles should be minimized to lower doses per vial in order to conduct immunization without having to wait for enough children and without worrying about vaccine waste. All infants who visit the hospital should be linked to immunization services.

Redesign of vaccine distribution networks

AbstractIn most low‐ and middle‐income countries supported by the World Health Organization's Expanded Program on Immunization, vaccines are distributed through a legacy medical supply chain that is typically not cost‐efficient. Vaccines require storage and transport in a temperature‐controlled environment; this requires a “cold” distribution chain with capacity constraints on cold storage and cold transport. We propose an approach to redesigning the vaccine distribution chain that includes locating a set of intermediate distribution centers (DCs) and determining the flow paths from the central store (where vaccines are received into a country) through one or more of these to health clinics where vaccination actually occurs. In addition, the transport vehicles to allocate to each flow path, and the cold storage devices to use at each clinic or intermediate DC are determined. The redesigned network does not have to follow the current four‐tiered, arborescent structure commonly found in practice, but can use alternative network structures. To redesign this network optimally, we develop a mixed‐integer programming (MIP) model that can be used for small‐to‐medium‐sized problems and also present a hybrid heuristic–MIP method to obtain good solutions for larger problems. Numerical results are shown using data reflecting distribution networks in several countries in sub‐Saharan Africa.

Immunogenicity of pulsatile-release PLGA microspheres for single-injection vaccination

The World Health Organization's Expanded Programme on Immunization has led to a dramatic rise in worldwide vaccination rates over the past 40years, yet 19.4 million infants remain underimmunized each year. Many of these infants have received at least one vaccine dose but may remain unprotected because they did not receive subsequent booster doses due to logistical challenges. This study aimed to develop injectable controlled release microparticles with kinetics that mimic common vaccine dosing regimens consisting of large antigen doses administered periodically over the course of months in order to eliminate the need for boosters. Sixteen poly(lactic-co-glycolic acid) (PLGA) microsphere formulations containing bovine serum albumin (BSA) as a model vaccine antigen were screened in vitro to determine their respective release kinetics. Three formulations that exhibited desirable pulsatile release profiles were then selected for studying immunogenicity in mice. Two low-dose microsphere formulations induced peak anti-BSA IgG antibody titers of 13.9±1.3 and 13.7±2.2 log2 compared to 15.5±1.5 log2 for a series of three bolus injections delivered at 0, 4, and 8weeks with an equivalent cumulative dose. Similarly, high-dose formulations induced peak antibody titers that were 16.1±2.1 log2 compared to 17.7±2.2 log2 for controls. All three microparticle formulations studied in vivo induced peak antibody titers that were statistically similar to bolus controls. These results suggest that pulsatile antigen release from polymeric microparticles is a promising approach for single-injection vaccination, which could potentially reduce the logistical burden associated with immunization in the developing world.

Immunization coverage of 12-23 months old children and associated factors in Jigjiga District, Somali National Regional State, Ethiopia.

BackgroundImmunization coverage in Ethiopia is less than the herd immunity level desired to prevent the spread of eight target diseases targeted by the World Health Organization’s Expanded Program of Immunization. In particular, the Somali region of the country still has by far the lowest level of immunization coverage. The objective of this study was to measure the immunization coverage of 12–23 months old children and associated factors in the urban and rural areas of Jigjiga district.MethodsA community based cross-sectional survey was conducted in 582 households with 12–23 months old children in two urban and four rural wards. The data were collected from mothers or caregivers through interviews based on pre-tested and structured questionnaires and from the review of vaccination cards. Data were processed using SPSS version 16. To identify factors associated with the immunization status of children, bivariate and multiple logistic regression analyses were worked out and the Hoshmer and Lemeshow’s goodness-of-fit was used to assess the fitness of multiple logistic regression model.ResultsThree–fourth (74.6%) of the children surveyed were ever vaccinated, whereas 36.6% were fully vaccinated. The immunization coverage rate from card assessment for Bacillus Calmette-Guérin was 41.8%, while for Oral Polio Vaccine Zero, Oral Polio Vaccine One /Pentavalent1, Oral Polio Vaccine Two /Pentavalent2, Oral Polio Vaccine Three /Pentavalent3, and measles were 10.4%, 41.1%, 33.9%, 27.5%, and 24.9%, respectively. Maternal literacy (AOR = 3.06, 95% CI = 1.64, 5.71), Tetanus Toxoid Vaccine (AOR = 2.43, 95% CI = 1.56, 3.77), place of delivery (AOR = 2.02, 95% CI = 1.24, 3.28), place of residence (AOR = 2.04, 95% CI = 1.33, 3.13), and household visits by health workers (AOR = 1.92, 95% CI = 1.17, 3.16), were found to be factors significantly associated with full immunization in the multivariate logistic regression analysis.ConclusionsThe overall immunization coverage was found to be low. Hence, to increase the immunization coverage and reduce the incidences of missed opportunity, delivery in the health institution should be promoted, the outreach activities of the health institutions should be strengthened and greater utilization of health services by mothers should be encouraged.

A planning model for the WHO-EPI vaccine distribution network in developing countries

In many developing countries, inefficiencies in the supply chain for the World Health Organization's Expanded Program on Immunization (EPI) vaccines are of grave concern; these inefficiencies result in thousands of people not being fully immunized and creates significant risk of disease epidemics. Thus, there is a great deal of interest in these countries in building tools to analyze and optimize how vaccines flow down several levels of the supply chain from manufacturers to vaccine recipients. This article develops a mathematical model for typical vaccine distribution networks in developing countries. This model has been successfully adapted for supply chains in three different countries (Niger, Thailand, and Vietnam), and its application to several issues of interest to public health administrators in developing countries is discussed.

Understanding interventions for improving routine immunization coverage in children in low- and middle-income countries: a systematic review protocol

BackgroundVirtually all low- and middle-income countries are dependent on the World Health Organization’s Expanded Program on Immunization for delivery of vaccines to children. The Expanded Program on Immunization delivers routine immunization services from health facilities free of charge. Understanding interventions for improving immunization coverage remains key in achieving universal childhood immunization.MethodsWe will conduct a systematic review that aims to assess the effectiveness of the full range of potential interventions to improve routine immunization coverage in children in low- and middle-income countries. We will include intervention studies, as well as observational studies. We will search the Cochrane Database of Systematic Reviews (CDSR), Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, electronic databases for eligible studies published by 31 August 2013. At least two authors will independently screen search outputs, select studies, extract data and assess the risk of bias (using separate criteria for interventions and observational studies); resolving any disagreements by discussion and consensus. The use of logic models and the Cochrane Complexity Matrix will be explored in order to better understand and contextualize studies. We will express the result of each study as a risk ratio with its corresponding 95% confidence intervals for dichotomous data, or mean difference with its standard deviation for continuous data. We will conduct meta-analysis for the same type of participants, interventions, study designs, and outcome measures where homogeneity of data allows. Use of harvest plots may be explored as an alternative. Heterogeneity will be assessed using the χ2 test of heterogeneity, and quantified using the I2 statistic. This protocol has not been registered with PROSPERO.DiscussionThis review will allow us to document evidence across a broad range of intervention types for improving routine immunization coverage in children and also distinguish between those that are well supported by evidence (to direct policy recommendations) and those that are not well supported (to direct research agenda).

Factors Associated with Dog Rabies Vaccination in Bhol, Philippines: Results of a Cross-Sectional Cluster Survey Conducted Following the Island-Wide Rabies Elimination Campaign

The Philippines has a long history of rabies control efforts in their dog populations; however, long-term success of such programmes and the goal of rabies elimination have not yet been realized. The Bohol Rabies Prevention and Elimination Program was developed as an innovative approach to canine rabies control in 2007. The objective of this study was to assess canine rabies vaccination coverage in the owned-dog population in Bohol and to describe factors associated with rabies vaccination 2 years after implementation of the programme. We utilized a cross-sectional cluster survey based on the World Health Organization's Expanded Programme on Immunization coverage survey technique. We sampled 460 households and collected data on 539 dogs residing within these households. Seventy-seven per cent of surveyed households reported owning at least one dog. The human-to-dog ratio was approximately 4 : 1, and the mean number of dogs owned per household was 1.6. Based on this ratio, we calculated an owned-dog population of almost 300 000. Overall, 71% of dogs were reported as having been vaccinated for rabies at some time in their lives; however, only 64% of dogs were reported as having been recently vaccinated. Dogs in our study were young (median age = 24 months). The odds of vaccination increased with increasing age. Dogs aged 12-23 months had 4.6 times the odds of vaccination compared to dogs aged 3-11 months (95% CI 1.8-12.0; P = 0.002). Confinement of the dog both day and night was also associated with increased odds of vaccination (OR = 2.1; 95% CI 0.9-4.9; P = 0.07), and this result approached statistical significance. While the programme is on track to meet its goal of 80% vaccination coverage, educational efforts should focus on the need to confine dogs and vaccinate young dogs.

Ensemble Modeling of the Likely Public Health Impact of a Pre-Erythrocytic Malaria Vaccine

The RTS,S malaria vaccine may soon be licensed. Models of impact of such vaccines have mainly considered deployment via the World Health Organization's Expanded Programme on Immunization (EPI) in areas of stable endemic transmission of Plasmodium falciparum, and have been calibrated for such settings. Their applicability to low transmission settings is unclear. Evaluations of the efficiency of different deployment strategies in diverse settings should consider uncertainties in model structure. An ensemble of 14 individual-based stochastic simulation models of P. falciparum dynamics, with differing assumptions about immune decay, transmission heterogeneity, and treatment access, was constructed. After fitting to an extensive library of field data, each model was used to predict the likely health benefits of RTS,S deployment, via EPI (with or without catch-up vaccinations), supplementary vaccination of school-age children, or mass vaccination every 5 y. Settings with seasonally varying transmission, with overall pre-intervention entomological inoculation rates (EIRs) of two, 11, and 20 infectious bites per person per annum, were considered. Predicted benefits of EPI vaccination programs over the simulated 14-y time horizon were dependent on duration of protection. Nevertheless, EPI strategies (with an initial catch-up phase) averted the most deaths per dose at the higher EIRs, although model uncertainty increased with EIR. At two infectious bites per person per annum, mass vaccination strategies substantially reduced transmission, leading to much greater health effects per dose, even at modest coverage. In higher transmission settings, EPI strategies will be most efficient, but vaccination additional to the EPI in targeted low transmission settings, even at modest coverage, might be more efficient than national-level vaccination of infants. The feasibility and economics of mass vaccination, and the circumstances under which vaccination will avert epidemics, remain unclear. The approach of using an ensemble of models provides more secure conclusions than a single-model approach, and suggests greater confidence in predictions of health effects for lower transmission settings than for higher ones.

A comparison of EPI sampling, probability sampling, and compact segment sampling methods for micro and small enterprises

Finding an efficient method for sampling micro- and small-enterprises (MSEs) for research and statistical reporting purposes is a challenge in developing countries, where registries of MSEs are often nonexistent or outdated. This lack of a sampling frame creates an obstacle in finding a representative sample of MSEs. This study uses computer simulations to draw samples from a census of businesses and non-businesses in the Tshwane Municipality of South Africa, using three different sampling methods: the traditional probability sampling method, the compact segment sampling method, and the World Health Organization's Expanded Programme on Immunization (EPI) sampling method. Three mechanisms by which the methods could differ are tested, the proximity selection of respondents, the at-home selection of respondents, and the use of inaccurate probability weights. The results highlight the importance of revisits and accurate probability weights, and the lesser effect of proximity selection on the samples' statistical properties.

Vaccination: rattling the supply chain

The first decade of this century was perhaps the most productive in the history of vaccine development, seeing the release of a plethora of new life-saving vaccines for rotavirus diarrhoea, types of meningitis and pneumonia, and for human papilloma-virus (HPV) infections that cause cervical cancer. We are in a very different situation now compared to 10 years ago;' says Dr Osman Mansoor at the United Nations Children's Fund (UNICEF) in New York. Mansoor, who is UNICEF's senior health adviser for the Expanded Programme on Immunization and New Vaccines, notes that more vaccines are in the pipeline. fact more than 80 vaccines are in the late stages of clinical testing, and 30 of them are designed to protect against major including dengue and malaria. At the same time, the global vaccine market is booming: since 2000, global revenue from the sale of vaccines has almost tripled reaching more than US$17 billion by mid-2008. While most of this expansion is accounted for by sales of new and more costly vaccines in industrialized countries, more vaccines are also reaching developing countries due to the efforts of the GAVI Alliance (formerly the Global Alliance for Vaccines and Immunization), a public-private partnership established in 2000 to increase immunization in poor countries. [ILLUSTRATION OMITTED] [ILLUSTRATION OMITTED] The World Health Organization (WHO) and UNICEF estimate that just over 80% of the world's children now have access to immunization, as measured by coverage of the third dose of DTP (diphtheria, tetanus and pertussis) vaccine, while an increasing number also have access to powerful new vaccines. In the past, countries relied on a package of vaccines against six diseases says Project Optimize Coordinator Modibo Dicko, referring to WHO's Expanded Programme on Immunization, which was launched in 1974. Now some countries are doubling the number of vaccines they offer. As encouraging as all this seems, the scaling up of immunization programmes and the introduction of new vaccines is putting an unprecedented strain on delivery systems that have not changed in decades. James Cheyne, a supply-chain consultant, who started his career in vaccine logistics in Burma (now Myanmar) in 1977, is in a good position to judge those systems since he has had a hand in designing several himself. Cheyne cites the unnecessary layering of distribution networks as one of his main concerns. Typically there is a central store that supplies the regional stores, which then feed the provincial stores and district stores that in turn supply the local health centres, he says, pointing out that while this layering made sense 30 years ago, because the lines of communication were weak, these days low-cost telecommunications technology has changed things. You don't need a store for each administrative level anymore because we have cell phones and the person from the health centre can call the central store directly; Cheyne says. Making better use of that kind of technology is a core aspect of the work being done by Project Optimize, a collaboration between WHO and PATH (formerly the Program for Appropriate Technology in Health), a nongovernmental organization. For Michel Zaffran, the director of Project Optimize, information technology is key in combating one of the biggest problems faced by vaccine distribution systems--overstock in supply. On the face of it the idea that immunization programmes are hampered by too much vaccine seems paradoxical. But, in fact, the overstocking of vaccines increases cold storage costs and generates waste (when vaccines are lost, damaged or not used before their expiry date, and when not all vials in a multi-dose vial get used). We want to have as little buffer stock as possible, but still we want to have enough vaccine to vaccinate the children, Zaffran says, arguing that this means putting in place information systems and technologies that give managers a real-time picture of how much stock they have throughout a country and whether the quantities meet the requirements of their immunization strategy. …

Safety and Immunogenicity of RTS,S/AS02D Malaria Vaccine in Infants

The RTS,S/AS malaria vaccine is being developed for delivery through the World Health Organization's Expanded Program on Immunization (EPI). We assessed the feasibility of integrating RTS,S/AS02D into a standard EPI schedule for infants. In this phase 2B, single-center, double-blind, controlled trial involving 340 infants in Bagamoyo, Tanzania, we randomly assigned 340 infants to receive three doses of either the RTS,S/AS02D vaccine or the hepatitis B vaccine at 8, 12, and 16 weeks of age. All infants also received a vaccine containing diphtheria and tetanus toxoids, whole-cell pertussis vaccine, and conjugated Haemophilus influenzae type b vaccine (DTPw/Hib). The primary objectives were the occurrence of serious adverse events during a 9-month surveillance period and a demonstration of noninferiority of the responses to the EPI vaccines (DTPw/Hib and hepatitis B surface antigen) with coadministration of the RTS,S/AS02D vaccine, as compared with the hepatitis B vaccine. The detection of antibodies against Plasmodium falciparum circumsporozoite and efficacy against malaria infection were secondary objectives. At least one serious adverse event was reported in 31 of 170 infants who received the RTS,S/AS02D vaccine (18.2%; 95% confidence interval [CI], 12.7 to 24.9) and in 42 of 170 infants who received the hepatitis B vaccine (24.7%; 95% CI, 18.4 to 31.9). The results showed the noninferiority of the RTS,S/AS02D vaccine in terms of antibody responses to EPI antigens. One month after vaccination, 98.6% of infants receiving the RTS,S/AS02D vaccine had seropositive titers for anticircumsporozoite antibodies on enzyme-linked immunosorbent assay (ELISA). During the 6-month period after the third dose of vaccine, the efficacy of the RTS,S/AS02D vaccine against first infection with P. falciparum malaria was 65.2% (95% CI, 20.7 to 84.7; P=0.01). The use of the RTS,S/AS02D vaccine in infants had a promising safety profile, did not interfere with the immunologic responses to coadministered EPI antigens, and reduced the incidence of malaria infection. (ClinicalTrials.gov number, NCT00289185.)

Serologic Response to Inactivated Poliovirus Vaccine: A Randomized Clinical Trial Comparing 2 Vaccination Schedules in Puerto Rico

The World Health Organization (WHO) recommends the discontinuation of oral poliovirus vaccine after eradication of wild poliovirus. Studies assessing inactivated poliovirus vaccine (IPV) immunogenicity in tropical countries, using the WHO Expanded Programme on Immunization (EPI) schedule, have been limited. We conducted a randomized clinical trial in Ponce, Puerto Rico. Infants were assigned to 1 of 2 study arms: those in the EPI arm received IPV at 6, 10, and 14 weeks of age, and those in the US arm received IPV at 2, 4, and 6 months of age. Neutralizing antibody titers against poliovirus types 1, 2, and 3 were tested on serum specimens obtained before administration of the first dose of IPV and 28-45 days after administration of the last dose of IPV. Seroconversion rates for the EPI (n=225) and US (n=230) arms, respectively, were 85.8% and 99.6% for poliovirus type 1 (P<.001), 86.2% and 100% for poliovirus type 2 (P<.001), and 96.9% and 99.1% for poliovirus type 3 (P=.08). Seroconversion rates were lower among infants in the EPI arm who had high maternal antibody levels for all 3 poliovirus types (P<.001). The EPI schedule resulted in lower seroconversion rates for poliovirus types 1 and 2. These results are relevant for tropical countries planning to use IPV in a posteradication environment.

Facilitating the WHO expanded program of immunization: the clinical profile of a combined diphtheria, tetanus, pertussis, hepatitis B and Haemophilus influenzae type b vaccine

Background: Vaccines are important weapons in the fight against infectious diseases. The World Health Organization (WHO) Expanded Program on Immunization (EPI) has been extended to include recommendations for hepatitis B and Haemophilus influenzae type b (Hib) vaccinations. The WHO has recommended that combined vaccines be used where possible, to reduce the logistic costs of vaccine delivery. This paper reviews the efficacy, safety and cost-effectiveness of Tritanrix-HB/Hib, the only commercially available combined diphtheria, tetanus, whole cell pertussis, hepatitis B and conjugated Hib vaccine. Methods: The immunogenicity and reactogenicity results of five published clinical trials involving Tritanrix-HB/Hib in a variety of immunization schedules and countries were reviewed. Based on these data and cost-effectiveness studies, an assessment of its suitability for use in national immunization programs was made. Results: Tritanrix-HB/Hib has shown excellent immunogenicity in clinical trials using a variety of schedules, with no reduced immunogenicity observed for any of the components of the combined vaccine. It has similar reactogenicity to DTPw vaccines alone. Pharmacoeconomic analyses have shown combined DTP-HB/Hib vaccines to be cost-effective compared to separate vaccines. Conclusions: Replacement of DTPw vaccination by Tritanrix-HB/Hib can be done without modifying the existing national immunization programs. This should facilitate widespread coverage of hepatitis B and Hib vaccinations and their rapid incorporation into the EPI.

Thermostabilization of live virus vaccines by heavy water (D 2O)

Eradication of poliomyelitis is based on the mass administration of oral poliovirus vaccine (OPV). Delivery of effective vaccines in the developing world, especially in tropical areas, is compromised when refrigeration cannot be assured. The OPV, prepared with three live attenuated polioviruses (Sabin strains, serotypes 1, 2 and 3), is considered to be the most thermolabile of vaccines in the World Health Organization's Expanded Programme on Immunization. To be effective, the initial concentration (potency) of each of the three component serotypes, measured in tissue culture infective doses, should not decrease by more than 0.5 log 10 before vaccine delivery. High concentration (1 M) of MgCl 2 is currently used as stabilizer for OPV. The stabilizing effect of D 2O was tested here on OPV strains. By diluting the viral suspension with D 2O-based salt and buffer solutions, in a manner similar to that involved in OPV production, an 87% concentration of D 2O in the final viral preparation was achieved. In severe conditions of testing (incubation for 3 days at 45°C), the Sabin 3 virus lost an average of 2.7 log 10 potency in the presence of 87% D 2O as compared to 3.0 log 10 in H 2O-based 1 M MgCl 2, and to 5.7 log 10 in the H 2O-based control solutions. When tested in a combined 87% D 2O and 1 M MgCl 2 treatment, the Sabin 3 virus lost only 1.3 log 10 potency after 3 days at 45°C. Similar thermostabilizing effects were obtained for Sabin 1 and Sabin 2 strains, but the level of stabilization was slightly lower. Tested in standard conditions at 37°C for 7 days, the infectivity of the three D 2O MgCl 2-treated OPV strains remained in the limit of requirements (≤0.5 log 10). The stabilizing effect of D 2O was also demonstrated on yellow fever 17D vaccine virus strain. D 2O, alone or in combination with other stabilizers such as MgCl 2, could thus be considered as a candidate for the improvement of live virus vaccine thermostability.

Increased seroprevalence of hepatitis B in dental personnel necessitates awareness of revised pediatric hepatitis B vaccine recommendations.

This article presents data regarding occurrence of hepatitis B in health care workers and children living in their households. Also reviewed are recent revisions in pediatric hepatitis B vaccine recommendations. The purpose of this discussion is twofold: to provide information to assist dental personnel in the decision-making process regarding vaccination of infants, children, and adolescents in their households; and to increase knowledge to facilitate educational presentations. In the United States from 1979 to 1989 the prevalence of new acute hepatitis B cases increased by 37 percent. An estimated 1.25 million people with chronic hepatitis B are capable of infecting those within their immediate environment, including their families. Studies indicate that dental health care workers, through occupational exposure, may have a 10 times greater risk of becoming a chronic hepatitis B carrier than the average citizen. The World Health Organizations's Expanded Programme on Immunizations recommends that children receive vaccination in populations where hepatitis B is prevalent. The three-pronged approach for reducing pediatric transmission includes: (1) vaccination of infants born to infected mothers, (2) routine vaccination of children born to hepatitis-seronegative mothers, (3) identification and vaccination of specific groups of adolescents. Comprehension of these changes may increase compliance regarding vaccination of children in our household, as well as enhancing our educational presentations to patients, the community, and professional societies.

Epidemiology of pertussis and reactions to pertussis vaccine.

It remains clear that pertussis is a dangerous infectious disease that is well-controlled in industrialized countries by widespread immunization. In the developing world, it remains a source of high morbidity and mortality because of previously inadequate immunization programs. However, because of the intense efforts of the World Health Organization's Expanded Programme on Immunization, the effects of pertussis have already been ameliorated and show promise of being within a decade of approximating the situation in the developed world. Pertussis can be controlled only by immunization; other measures such as antimicrobial therapy offer negligible benefit. A problem that has been addressed in recent years is the excessive reactivity of whole-cell pertussis vaccine, which undoubtedly includes components of the organism that are irrelevant to the induction of immunity and are excessively reactive. Although epidemiologic studies appear to have largely, if not completely, absolved pertussis vaccine of responsibility for inducing death or permanent neurologic disability, a less reactive vaccine is highly desirable, not only to promote acceptance of a full course of immunization for the world's children but also for simple humanitarian reasons. Additionally, it has become evident that, because of waning immunity, pertussis increasingly occurs in adults. A less reactive vaccine would offer opportunity for reinforcement of immunity beyond childhood. The development of better, though as yet incomplete, understanding of the biology of Bordetella pertussis and its relation to humanity offers the opportunity for the production of less reactive vaccines free of irrelevant components. Acellular pertussis vaccines have been used exclusively in Japan for more than 10 years, and one such preparation, combined with diphtheria and tetanus toxoids, was licensed in the United States in late 1991 for use as the fourth and fifth doses of DTP, given at 15 months and prior to school entry. Field trials of this and other acellular DTP preparations are currently under way to determine their clinical efficacy in infants. It is probable that, within a very few years, whole-cell pertussis vaccine will be replaced by these newer preparations and that, in addition, the acellular product will be combined with other antigens, such as Haemophilus influenzae type b vaccine.

A Chance to Live

June Goodfield has written an interesting book about the effort to immunize the world's children. Written as a companion to a television documentary, the book is geared to an educated lay audience. In the first part, the author describes the impact of the vaccine-preventable diseases targeted by the World Health Organization's Expanded Programme on Immunization (EPI)—diphtheria, tetanus, pertussis, poliomyelitis, measles, tuberculosis—and the initiation in 1974 and early difficulties of the EPI. She also describes the complexities of vaccine manufacture, the problems in getting vaccine from the manufacturer to the child (including transportation issues and the necessity for a cold chain to prevent inactivation of vaccines by heat), and the inadequacies of the health care delivery system in developing countries. She then discusses the different agendas of agencies that work in immunization (particularly the World Health Organization [WHO] and the United Nations Children's Fund [UNICEF]) and the differences in personality and

Childhood Immunization in the State of Qatar: Implications for Improving Coverage

In Qatar, there is evidence of underuse of the immunization services despite easy access to health care. We therefore undertook a prospective study to determine the vaccination status and, more importantly, the reasons for inadequate immunization of a group of 255 preschool children attending the outpatient care facilities in Doha. A questionnaire was used to obtain relevant information, including parent's educational background. Sixty-six percent of the children were fully immunized for their age group, 12% were partially immunized, and 12% were not immunized. Eighty-eight percent had received their first dose of DPT/OPV, but only 57% had received their first booster by 18 months of age; 76% had received three doses of DPT/OPV. The main reasons for nonimmunized status were misinformation and lack of awareness in parents about vaccination. Parental oversight, misinformation, and medical deferral were the main reasons for partial immunization. Parents of unimmunized children were often illiterate. In Qatar, establishment of an aggressive ongoing public education campaign, as well as strict implementation of the World Health Organization's Expanded Programme on Immunization's policy of screenign all children at every health care contact for the need for vaccination, should substantially increase immunization coverage. Implementation of a recall system for defaulters should also lead to improved immunization rates.

Vaccination strategies in developing countries.

By 1990 it is hoped that all of the world's infants will have access to immunization services and that these services will then continue indefinitely. The link between people and health services, including immunization, can only be forged and maintained by an effective system of delivery and support to all health workers. A careful choice of strategies for this delivery system and an understanding of local cultural attitudes and behaviour is vital if this link is to be effective. Health workers will have to be trained and then supported in the field by regular contact with their supervisors. They will also need continuous, reliable, predictable and adequate supplies of equipment, drugs, vaccines, fuel and money, including salaries. Immunization is cost effective as a health intervention, but an effective programme of immunization can contribute much more than just vaccines, if it is developed in the context of primary health care (PHC) as originally proposed in 1978 at the conference in Alma Ata.

Prospects for the eradication of infectious diseases.

The meaning of eradication, which is an irreversible conclusion, is considered primarily to distinguish it from elimination, which is reversible from outside the area. Poliomyelitis and measles are at present the diseases for which conditions most favor an attempt to produce eradication. Poliomyelitis has now reached a frequency in the developing world as high as it was in the prevaccine era of the United States. The use of oral vaccine is a deliberate attempt to substitute the wild-type polioviruses in the community with the vaccine-like viruses derived from the vaccine itself. Mass use of vaccine in all children less than five years of age on a single day twice in a year has produced a critical decrease in the incidence of the disease in Brazil. Following determined efforts to achieve immunization of at least 95% of the population, the United States is now nearing the state of complete freedom from the transmission of measles virus. The use of diploid cells for making vaccine has enabled the virus to be given as an aerosol to babies less than six months of age and would be of particular value in developing countries. The high transmissibility of measles makes a severe demand for vaccine, but so long as the uptake of vaccine reaches at least 90%, the successful elimination of measles is extremely probable.