Strategies for the global eradication of poliomyelitis by the year 2000

Oral polio vaccine stockpile modeling: insights from recent experience

BACKGROUND

Achieving polio eradication requires ensuring the delivery of sufficient supplies of the right vaccines to the right places at the right times. Despite large global markets, decades of use, and large quantity purchases of polio vaccines by national immunization programs and the Global Polio Eradication Initiative (GPEI), forecasting demand for the oral poliovirus vaccine (OPV) stockpile remains challenging.

RESEARCH DESIGN AND METHODS

We review OPV stockpile experience compared to pre-2016 expectations, actual demand, and changes in GPEI policies related to the procurement and use of type 2 OPV vaccines. We use available population and immunization schedule data to explore polio vaccine market segmentation, and its role in polio vaccine demand forecasting.

RESULTS

We find that substantial challenges remain in forecasting polio vaccine needs, mainly due to (1) deviations in implementation of plans that formed the basis for earlier forecasts, (2) lack of alignment of tactics/objectives among GPEI partners and other key stakeholders, (3) financing, and (4) uncertainty about development and licensure timelines for new polio vaccines and their field performance characteristics.

CONCLUSIONS

Mismatches between supply and demand over time have led to negative consequences associated with both oversupply and undersupply, as well as excess costs and potentially preventable cases.

Poliovirus returns to the UK after nearly 40 years: current efforts and future recommendations

On 22 June 2022, the UK Health Security Agency declared a 'rare national incidence' after finding poliovirus in sewage in London for the first time in nearly 40 years. Although no cases of the disease or accompanying paralysis have been documented, the general public's risk is considered minimal. However, public health experts recommend that families are up to date on their polio vaccines to decrease the chance of harm. This article discusses the epidemiology of poliovirus by examining the aetiology of the disease and current mitigation policies implemented to prevent the spread of type 2 vaccine-deceived poliovirus in the UK. Finally, by examining the clinical features of polio, which range from mild gastroenteritis episodes, respiratory sickness, malaise and severe paralysis type, this article offers an advice on particular therapies and tactics to avoid poliovirus outbreaks and other future outbreaks.

Immunogenicity and Safety of Inactivated Sabin-Strain Polio Vaccine "PoliovacSin": Clinical Trials Phase I and II

Global polio eradication requires both safe and effective vaccines, and safe production processes. Sabin oral poliomyelitis vaccine (OPV) strains can evolve to virulent viruses and result in poliomyelitis outbreaks, and conventional inactivated poliomyelitis vaccine (Salk-IPV) production includes accumulation of large stocks of neurovirulent wild polioviruses. Therefore, IPV based on attenuated OPV strains seems a viable option. To increase the global supply of affordable inactivated vaccine in the still not-polio free world we developed an IPV made from the Sabin strains–PoliovacSin. Clinical trials included participants 18–60 years of age. A phase I single-center, randomized, double-blind placebo-controlled clinical trial included 60 participants, who received one dose of PoliovacSin or Placebo. A phase II multicenter, randomized, double-blind, comparative clinical trial included 200 participants, who received one dose of PoliovacSin or Imovax Polio. All vaccinations were well tolerated, and PoliovacSin had a comparable safety profile to the Placebo or the reference Imovax Polio preparations. A significant increase in neutralizing antibody levels to polioviruses types 1–3 (Sabin and wild) was observed in PoliovacSin and Imovax Polio vaccinated groups. Therefore, clinical trials confirmed good tolerability, low reactogenicity, and high safety profile of the PoliovacSin and its pronounced immunogenic properties. The preparation was approved for clinical trials involving infants.

Ontology-based Precision Vaccinology for Deep Mechanism Understanding and Precision Vaccine Development

Vaccination is one of the most important innovations in human history. It has also become a hot research area in a new application - the development of new vaccines against non-infectious diseases such as cancers. However, effective and safe vaccines still do not exist for many diseases, and where vaccines exist, their protective immune mechanisms are often unclear. Although licensed vaccines are generally safe, various adverse events, and sometimes severe adverse events, still exist for a small population. Precision medicine tailors medical intervention to the personal characteristics of individual patients or sub-populations of individuals with similar immunity-related characteristics. Precision vaccinology is a new strategy that applies precision medicine to the development, administration, and post-administration analysis of vaccines. Several conditions contribute to make this the right time to embark on the development of precision vaccinology. First, the increased level of research in vaccinology has generated voluminous "big data" repositories of vaccinology data. Secondly, new technologies such as multi-omics and immunoinformatics bring new methods for investigating vaccines and immunology. Finally, the advent of AI and machine learning software now makes possible the marriage of Big Data to the development of new vaccines in ways not possible before. However, something is missing in this marriage, and that is a common language that facilitates the correlation, analysis, and reporting nomenclature for the field of vaccinology. Solving this bioinformatics problem is the domain of applied biomedical ontology. Ontology in the informatics field is human- and machine-interpretable representation of entities and the relations among entities in a specific domain. The Vaccine Ontology (VO) and Ontology of Vaccine Adverse Events (OVAE) have been developed to support the standard representation of vaccines, vaccine components, vaccinations, host responses, and vaccine adverse events. Many other biomedical ontologies have also been developed and can be applied in vaccine research. Here, we review the current status of precision vaccinology and how ontological development will enhance this field, and propose an ontology-based precision vaccinology strategy to support precision vaccine research and development.

Animal Models and Alternatives in the Quality Control of Vaccines: Are In Vitro Methods or In Vivo Methods the Scientific Equivalent of the Emperor's New Clothes?

In the quality control of vaccine batches, the potency testing of inactivated vaccines is one of the areas requiring very large numbers of animals, which usually suffer significant distress as a result of the experimental procedures employed. This article deals with the potency testing of diphtheria and tetanus toxoids, two vaccines which are used extensively throughout the world. The relevance of the potency test prescribed by the European Pharmacopoeia monographs is questioned. The validity of the potency test as a model for the human response, the ability of the test to be standardised, and the relevance of the test in relation to the quality of the product are discussed. It is concluded that the potency test has only limited predictive value for the antitoxin responses to be expected in recipients of these toxoids.

An alternative approach for estimating the potency of toxoid batches is discussed, in which a distinction is made between estimation of the immunogenic potency of the first few batches obtained from a seed lot and monitoring the consistency of the quality of subsequent batches. The use of animals is limited to the first few batches. Monitoring the consistency of the quality of subsequent batches is based on in vitro test methods.

Factors which hamper the introduction and acceptance of the alternative approach are considered. Finally, proposals are made for replacement, reduction and/or refinement (the Three Rs) in the use of animals in the routine potency testing of toxoids.

Statistical and Ontological Analysis of Adverse Events Associated with Monovalent and Combination Vaccines against Hepatitis A and B Diseases

Vaccinations often induce various adverse events (AEs), and sometimes serious AEs (SAEs). While many vaccines are used in combination, the effects of vaccine-vaccine interactions (VVIs) on vaccine AEs are rarely studied. In this study, AE profiles induced by hepatitis A vaccine (Havrix), hepatitis B vaccine (Engerix-B), and hepatitis A and B combination vaccine (Twinrix) were studied using the VAERS data. From May 2001 to January 2015, VAERS recorded 941, 3,885, and 1,624 AE case reports where patients aged at least 18 years old were vaccinated with only Havrix, Engerix-B, and Twinrix, respectively. Using these data, our statistical analysis identified 46, 69, and 82 AEs significantly associated with Havrix, Engerix-B, and Twinrix, respectively. Based on the Ontology of Adverse Events (OAE) hierarchical classification, these AEs were enriched in the AEs related to behavioral and neurological conditions, immune system, and investigation results. Twenty-nine AEs were classified as SAEs and mainly related to immune conditions. Using a logistic regression model accompanied with MCMC sampling, 13 AEs (e.g., hepatosplenomegaly) were identified to result from VVI synergistic effects. Classifications of these 13 AEs using OAE and MedDRA hierarchies confirmed the advantages of the OAE-based method over MedDRA in AE term hierarchical analysis.

Immunogenicity and safety of combined adsorbed low-dose diphtheria, tetanus and inactivated poliovirus vaccine (REVAXIS (®)) versus combined diphtheria, tetanus and inactivated poliovirus vaccine (DT Polio (®)) given as a booster dose at 6 years of age

This randomized, comparative, phase-IIIb study conducted in France aimed to demonstrate whether seroprotection against diphtheria, tetanus and poliomyelitis 1 month after a single dose of REVAXIS (low-dose diphtheria) is non-inferior to seroprotection 1 month after a single dose of DT Polio (standard-dose diphtheria), both vaccines being given as a second booster to healthy children at 6 years of age. Children were randomly assigned to receive a single intramuscular dose of REVAXIS or DT Polio. Primary endpoints were the 1-month post-booster seroprotection rates for diphtheria, tetanus and poliovirus type-1, -2 and -3 antigens. Secondary endpoints were immunogenicity and safety observations. Of 788 children screened, 760 were randomized: REVAXIS group, 384 children; DT Polio group, 376 children. No relevant difference in demographic characteristics at baseline was observed between REVAXIS and DT Polio groups. Non-inferiority of REVAXIS compared with DT Polio for seroprotection was demonstrated against diphtheria (respectively 98.6% and 99.3%), tetanus (respectively 99.6% and 100%), and poliovirus antigens (100% for each types in both groups). No allergic reactions to REVAXIS were reported. A benefit/risk ratio in favor of REVAXIS was suggested by the trend towards a better tolerability of REVAXIS compared with DT Polio regarding the rate of severe solicited injection-site reactions. The results support the use of REVAXIS as a booster at 6 years of age in infants who previously received a three-dose primary series within the first 6 months of life and a first booster including diphtheria, tetanus and poliovirus vaccine(s) given before 2 years of age.

Molecular epidemiology of wild poliovirus type 1 circulation in West and Central Africa, from 1997 to 1999, using genotyping with a restriction fragment length polymorphism assay

Virological surveillance is an important element in the Polio Eradication Initiative to provide information rapidly about circulating wild polioviruses. Molecular tools have been developed to identify the serotype of the poliovirus strains and whether they are of vaccine or wild origin (intratypic differentiation) and to perform the molecular epidemiology of wild strains. The main objective of this study was to show that restriction fragment length polymorphism (RFLP) is a tool that can be used for molecular epidemiology of wild polioviruses. This is retrospective study of poliovirus type 1 strains received at the Institut Pasteur of Bangui (IPB), a WHO Regional Reference Laboratory for Africa, since 1994. We describe our experience with isolates from Western and Central Africa and show a positive correlation between the genotypes as determined by sequencing the gene for the VP1 capsid protein and the RFLP patterns. Although genomic sequencing is the gold standard method for detailed molecular epidemiology analysis of poliovirus isolates, these results show that RFLP is a potentially valuable tool for molecular epidemiological analysis of poliovirus type 1 strains: it could be used by many laboratories as a rapid method for ITD and genotype screening where sequencing capacity is not readily available.

Mass vaccination campaigns for polio eradication: an essential strategy for success

Effective vaccines against poliomyelitis became available in the mid-1950s and early 1960s. Mass campaigns were an integral part of early control efforts. Thereafter, polio vaccines were used largely in routine childhood programs. The resolution in 1988 to eradicate polio globally led to the development of appropriate strategies to achieve this goal, including mass vaccination campaigns (i.e., national immunization days, sub-national immunization days and mop-up activities), to achieve the highest possible coverage in the shortest possible time. Unlike other vaccines, mass campaign use of oral poliovirus vaccine enhances the immunogenicity of this vaccine, primarily due to: (1) the decrease in the prevalence of other enteroviruses that potentially interfere with seroconversion; and (2) the secondary spread of vaccine virus from vaccinees to close contacts, resulting in seroconversion of some unvaccinated contacts. To reach the highest possible coverage, detailed planning, meticulous execution, careful supervision and standardized monitoring are critical. A number of innovative approaches to improve the quality and/or coverage have become the 'standard' of supplemental immunization activities. These mass campaigns have led to dramatic decreases in the incidence of polio. This chapter reviews the scientific, operational and programmatic data on mass campaign use of polio vaccines, and summarize the lessons learnt from implementing the mass vaccination strategies used to eradicate poliomyelitis globally.

Vaccines and immunotherapies for the prevention of infectious diseases having cutaneous manifestations

Although the development of antimicrobial drugs has advanced rapidly in the past several years, such agents act against only certain groups of microbes and are associated with increasing rates of resistance. These limitations of treatment force physicians to continue to rely on prevention, which is more effective and cost-effective than therapy. From the use of the smallpox vaccine by Jenner in the 1700s to the current concerns about biologic warfare, the technology for vaccine development has seen numerous advances. The currently available vaccines for viral illnesses include Dryvax for smallpox; the combination measles, mumps, and rubella vaccine; inactivated vaccine for hepatitis A; plasma-derived vaccine for hepatitis B; and the live attenuated Oka strain vaccine for varicella zoster. Vaccines available against bacterial illnesses include those for anthrax, Haemophilus influenzae, and Neisseria meningitidis. Currently in development for both prophylactic and therapeutic purposes are vaccines for HIV, herpes simplex virus, and human papillomavirus. Other vaccines being investigated for prevention are those for cytomegalovirus, respiratory syncytial virus, parainfluenza virus, hepatitis C, and dengue fever, among many others. Fungal and protozoan diseases are also subjects of vaccine research. Among immunoglobulins approved for prophylactic and therapeutic use are those against cytomegalovirus, hepatitis A and B, measles, rabies, and tetanus. With this progress, it is hoped that effective vaccines soon will be developed for many more infectious diseases with cutaneous manifestations.

Thermostabilization of egg grown influenza viruses

The observation that the addition of deuterium oxide to tissue culture cell harvests stabilized trivalent oral poliovirus vaccine prompted us to examine the effect of deuterium oxide on stabilization of other licensed and experimental live viral vaccines. The most striking effect afforded by deuterium oxide was on stabilization of live, attenuated influenza A and B vaccine candidates grown in the allantoic cavity of embryonated eggs. Thermostabilization with deuterium oxide is much greater than seen with standard stabilization of these live influenza vaccines with sucrose-phosphate-glutamate. Subsequently, we have shown that a similar, stabilization is provided by diluting egg allantoic fluid in water or minimal essential medium. The mechanism of action has been explored but remains uncertain. The implications of being able to stabilize influenza after harvesting from eggs have practical application for utilization of live influenza vaccines and provides a possible way to increase and standardize the potency of inactivated vaccines that may partially degrade in the inimical environment of allantoic fluid during growth and before final vaccine purification and stabilization.

Natural genetic exchanges between vaccine and wild poliovirus strains in humans

In a previous study of poliovirus vaccine-derived strains isolated from patients with vaccine-associated paralytic poliomyelitis (VAPP) (9, 11), we reported that a high proportion (over 50%) of viruses had a recombinant genome. Most were intertypic vaccine/vaccine recombinants. However, some had restriction fragment length polymorphism (RFLP) profiles different from those of poliovirus vaccine strains. We demonstrate here that five such recombinants, of 88 VAPP strains examined, carried sequences of wild (nonvaccine) origin. To identify the parental wild donor of these sequences, we used RFLP profiles and nucleotide sequencing to look for similarity in the 3D polymerase-coding region of 61 wild, cocirculating poliovirus isolates (43 type 1, 16 type 2, and 2 type 3 isolates). In only one case was the donor identified, and it was a wild type 1 poliovirus. For the other four vaccine/wild recombinants, the wild parent could not be identified. The possibility that the wild sequences were of a non-poliovirus-enterovirus origin could not be excluded. Another vaccine/wild recombinant, isolated in Belarus from a VAPP case, indicated that the poliovirus vaccine/wild recombination is not an isolated phenomenon. We also found wild polioviruses (2 of 15) carrying vaccine-derived sequences in the 3' moiety of their genome. All these results suggest that genetic exchanges with wild poliovirus and perhaps with nonpoliovirus enteroviruses, are also a natural means of evolution for poliovirus vaccine strains.

Immunogenicity and safety of a trivalent tetanus, low dose diphtheria, inactivated poliomyelitis booster compared with a standard tetanus, low dose diphtheria booster at six to nine years of age. Munich Vaccine Study Group

OBJECTIVE

To compare the immunogenicity and safety of a trivalent tetanus-diphtheria (low toxoid content)-inactivated poliomyelitis vaccine, Td-IPV (Revaxis; Pasteur Merièux), with a tetanus-diphtheria (low toxoid content) vaccine, Td (Td-Impfstoff Mérieux; Pasteur Merièux), when administered as a booster to children age 6 to 9 years.

METHODS

A group of 301 children were randomized and vaccinated with Td-IPV (n = 150) or Td (n = 151) in this open, controlled, multicenter trial. Serum specimens were obtained before and 28 days after vaccination. Safety was assessed for up to 28 days postvaccination by parental diary cards. Solicited local and systemic reactions were recorded for 7 days after vaccination.

RESULTS

Seroprotection (enzyme-linked immunosorbent assay titer, > or =0.10 IU/ml) against tetanus and diphtheria was induced by either Td-IPV or Td in all subjects. Tetanus and diphtheria geometric mean titer were higher after Td (34.0 and 5.74 IU/ml) than after Td-IPV (15.9 and 4.38 IU/ml). All subjects boosted with Td-IPV were seroprotected against each type of poliovirus (neutralizing antibody titer, > or =5/dilution). The most frequently reported solicited local and systemic symptoms were pain triggered by movement of the arm (54% vs. 39.1%) and headache (17.3% vs. 7.3%), after Td-IPV and Td, respectively. All other events were similar between the two groups. Reactions were generally mild and all were temporary.

CONCLUSIONS

A booster dose of Td-IPV induced in all children seroprotection against tetanus, diphtheria and poliomyelitis. The overall safety profile of the two vaccines was acceptable.

Eradication of vaccine-preventable diseases

Eradication is the permanent reduction to zero of the worldwide incidence of infection caused by a specific agent as a result of deliberate efforts; intervention measures are no longer needed. To date, the only infectious disease that has been eradicated is smallpox. Poliomyelitis is targeted for eradication by the year 2000, and the eradication initiative is well under way, with the Western Hemisphere certified as being polio-free and more than one year having passed since polio cases occurred in the Western Pacific Region of the World Health Organization. A review of the technical feasibility of eradicating other diseases preventable by vaccines currently licensed for civilian use in the United States indicates that measles, hepatitis B, mumps, rubella, and possibly disease caused by Haemophilus influenzae type b are potential candidates. From a practical point of view, measles seems most likely to be the next target. Global capacity to undertake eradication is limited, and care must be taken to ensure that a potential measles eradication effort does not impede achievement of polio eradication. Even in the absence of eradication, major improvements in control are both feasible and necessary with existing vaccines. New and improved vaccines may give further possibilities of eradication in the future. Eradication represents the ultimate in sustainability and social justice.

Australia's contribution to global polio eradication initiatives

OBJECTIVE

To provide evidence according to the requirements of the Global Commission for Certification of Poliomyelitis Eradication that poliomyelitis has been eliminated in Australia.

METHODS

Documentation of the surveillance of poliomyelitis, the presence of a comprehensive national immunisation program, and a network of laboratories for viral diagnosis. Active surveillance of acute flaccid paralysis (AFP) cases was initiated in 1995 to prove that poliovirus does not cause such paralysis. Australia is also evaluating the surveillance of AFP through a retrospective hospital based study.

RESULTS

The last case in Australia of polio due to wild poliovirus was seen in 1978 and the last case of vaccine-associated paralytic poliomyelitis detected by serology was in 1994. The latest immunisation coverage figures for OPV3 for children under one year of age is 85.6%. The Australian National Polio Reference Laboratory has tested 821 enteroviruses since 1994 and have not identified any wild poliovirus. The average rate of non-polio AFP based on 111 cases investigated for the period 1995-98 is 0.71 per 100,000 under the age of 15 years. Stool samples were collected from only 21% of cases.

CONCLUSION

The process of certification of the eradication of poliomyelitis in Australia is almost complete. Although immunisation coverage is high, improvement in AFP surveillance and stool collection is vital for the certification process. The next challenge is the containment of polioviruses.

IMPLICATIONS

Although Australia and other Western Pacific countries are likely to be certified as wild-polio free in 2000, a comprehensive immunisation program and surveillance must continue for three years after global certification (expected 2003-04).

Paralytic poliomyelitis associated with live oral poliomyelitis vaccine in child with HIV infection in Zimbabwe: case report

OBJECTIVE

To describe a complication of oral vaccination with live, attenuated poliomyelitis virus in a child infected with HIV.

DESIGN

Case report.

SETTING

Teaching hospital in Harare, Zimbabwe.

SUBJECTS

A boy of 41/2 years and his mother.

MAIN OUTCOME MEASURES

Results of clinical and laboratory investigations.

RESULTS

Two weeks after receiving the second dose of oral poliomyelitis vaccine during national immunisation days the child developed paralysis of the right leg. He had a high titre of antibodies against poliovirus type 2, as well as antibodies against HIV-1, a low CD4 count, a ratio of CD4 to CD8 count of 0.47, and hypergammaglobulinaemia. He did not have any antibodies against diphtheria, tetanus, or poliovirus types 1 and 3, although he had been given diphtheria, tetanus, and pertussis and oral polio vaccines during his first year and a booster of the diphtheria, tetanus, and pertussis vaccine at 24 months. He had no clinical symptoms of AIDS, but his mother had AIDS and tuberculosis.

CONCLUSION

Paralytic poliomyelitis in this child with HIV infection was caused by poliovirus type 2 after oral poliomyelitis vaccine.

The pregnant traveler

The care of the pregnant traveler is both challenging and rewarding. It requires clinical information and skills that are derived from many disciplines. This article reviews preparatory guidelines for safe travel by the pregnant mother and her most important travel companion, the developing fetus. Issues considered are pretravel risk assessment, immunizations, and prevention of travelers' diarrhea and hepatitis. The safety and efficacy of malaria chemoprophylaxis in the present context of widespread multidrug-resistant malaria is discussed, and guidelines are offered for both prevention and treatment. A safety profile of commonly used travel medications, antibiotics, and antiparasitic drugs is reviewed.

Molecular typing of enteroviruses: current status and future requirements. The European Union Concerted Action on Virus Meningitis and Encephalitis

Human enteroviruses have traditionally been typed according to neutralization serotype. This procedure is limited by the difficulty in culturing some enteroviruses, the availability of antisera for serotyping, and the cost and technical complexity of serotyping procedures. Furthermore, the impact of information derived from enterovirus serotyping is generally perceived to be low. Enteroviruses are now increasingly being detected by PCR rather than by culture. Classical typing methods will therefore no longer be possible in most instances. An alternative means of enterovirus typing, employing PCR in conjunction with molecular genetic techniques such as nucleotide sequencing or nucleic acid hybridization, would complement molecular diagnosis, may overcome some of the problems associated with serotyping, and would provide additional information regarding the epidemiology and biological properties of enteroviruses. We argue the case for developing a molecular typing system, discuss the genetic basis of such a system, review the literature describing attempts to identify or classify enteroviruses by molecular methods, and suggest ways in which the goal of molecular typing may be realized.

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.

Safety and immunogenicity of two inactivated poliovirus vaccines in combination with an acellular pertussis vaccine and diphtheria and tetanus toxoids in seventeen- to nineteen-month-old infants

OBJECTIVES

To compare the safety and immunity of an acellular pertussis vaccine containing pertussis toxoid, filamentous hemagglutinin, 69 kd protein, fimbriae 2 and 3 combined with diphtheria and tetanus toxoids given as single or separate injection with inactivated poliovirus vaccine (MRC-5-or Vero cell-derived) or live attenuated polio vaccine.

METHODS

A total of 425 healthy children between 17 and 19 months of age who were receiving the fourth dose of their routine immunization series were randomly allocated to receive either the acellular pertussis vaccine and oral poliovirus vaccine or one of two inactivated poliovirus vaccines as a combined injection or separate injections.

RESULTS

Although minor adverse events were commonly reported, differences between the groups were few. Fever and decreased feeding were less common in recipients of live attenuated poliovirus vaccine than the combination vaccine containing MRC-5 cell-derived inactivated poliovirus vaccine. A significant antibody response was demonstrated in all groups against all the antigens contained in the vaccines. Antibodies against poliovirus were higher in the groups immunized with the inactivated poliovirus vaccine than the live attenuated vaccine. Anti-69 kd protein antibodies were higher in the group given the MRC-5 cell-derived inactivated poliovirus vaccine as a combined injection than in the group given the separate injection or the group immunized with the live attenuated poliovirus vaccine.

CONCLUSION

The five-component acellular pertussis vaccine combined with diphtherid and tetanus toxoids is safe and immunogenic when combined with either MRC-5- or Vero cell-derived inactivated poliovirus vaccine. This will facilitate the implementation of acellular pertussis vaccine and the movement to inactivated poliovirus vaccine programs.

Molecular detection of an importation of type 3 wild poliovirus into Canada from The Netherlands in 1993

During the fall and winter of 1992-1993 an outbreak of wild poliovirus type 3-associated poliomyelitis involving 71 patients occurred in The Netherlands. Almost all of the individuals involved in the outbreak belonged to an orthodox religious denomination that prohibits vaccination. A surveillance was initiated to determine if there had been an importation of this same strain of wild poliovirus into a southern Alberta community with a similar religious affiliation. Viral culture of stool samples from consenting individuals in the community resulted in viral isolates which typed as poliovirus type 3. Sequencing of amplicons generated from both the 5' nontranslated region and the VP1/2A portion of the genomes from representative poliovirus isolates indicated a greater than 99% genetic similarity to the strain from The Netherlands. The results of this study show that the utilization of PCR-based diagnostics offers an important molecular tool for the concise and rapid surveillance of possible cases of wild poliovirus importation into communities with individuals at risk for infection.

Effect of diarrhea on the humoral response to oral polio vaccination

OBJECTIVE

The purpose of this study was to measure the effect of concurrent diarrheal illness on seroconversion to trivalent oral polio vaccine (OPV).

METHODS

Six- to 16-week-old infants with acute diarrhea and age-matched controls received single doses of OPV at enrollment, 4 weeks after enrollment and 8 weeks after enrollment. Serum specimens were obtained at enrollment, before the second OPV dose and 4 weeks after the third OPV dose for measurement of antibody titers to polio virus by the microneutralization assay.

RESULTS

Four weeks after the first OPV dose, the serologic responses to poliovirus types 2 and 3 in the case cohort were lower by 26 and 34%, respectively, than in the control cohort (P < 0.002 for both comparisons). Poliovirus type 2 and 3 geometric mean antibody titers in the diarrhea cohort were approximately 50% of the geometric mean antibody titers in the control cohort (235 (95% confidence interval (CI) 154 to 359) vs. 446 (95% CI 350 to 569) and 64 (95% CI 45 to 90) vs. 112 (95% CI 88 to 143), respectively, P < 0.01 for both comparisons). After the third OPV dose the seroconvertion rates to poliovirus types 2 and 3 each remained about 10% lower in the case cohort than in the control cohort, but the differences were not statistically significant.

CONCLUSION

Concurrent acute diarrhea adversely affects seroconvertion rates of type 2 and 3 polioviruses among infants in Bangladesh receiving the first dose of trivalent OPV.

Comparative study of five methods for intratypic differentiation of polioviruses

A coded panel of 90 poliovirus isolates, 30 of each of the three known serotypes, was used to evaluate five methods for the intratypic differentiation of polioviruses: (i) an enzyme-linked immunosorbent assay with polyclonal cross-absorbed antisera (PAb-E), (ii) a neutralization assay with type-specific monoclonal antibodies (MAb-N), (iii) a restriction fragment length polymorphism (RFLP) assay, (iv) a Sabin vaccine strain-specific PCR assay, and (v) a Sabin vaccine strain-specific cRNA probe hybridization (ProHyb) assay. Sequence analysis was used for the definitive characterization of the strains. The panel was distributed to five laboratories; each laboratory analyzed the strains by at least two methods. Each method was used by three or four laboratories. The total performance scores (percentage correct results per number of tests) of the five methods were 96.7% for PAb-E, 93.9% for MAb-N, 91.9% for RFLP assay, 93.3% for Sabin vaccine strain-specific PCR, and 97.4% for Sabin vaccine strain-specific ProHyb. Consistent results were obtained by each laboratory for 88 of 90 isolates (97.8%) examined by PAb-E, 81 of 90 isolates (90.0%) examined by MAb-N, 78 of 90 isolates (86.7%) examined by RFLP assay, 81 of 90 isolates (90.0%) examined by PCR, and 89 of 90 isolates (98.9%) examined by ProHyb assay. Six strains were classified differently by different methods. It is recommended that at least two methods be used for the intratypic differentiation of poliovirus isolates, and each method should be based on a different principle (i.e., antigenic properties and nucleotide sequence composition). If two assays yield discrepant results, further characterization, preferably by partial sequence determination, will be required for correct identification.

Poliomyelitis in The Netherlands: a review of population immunity and exposure between the epidemics in 1978 and 1992

An overview of serological and virological studies on poliomyelitis in the Netherlands between two epidemics in 1978 and 1992 is given. Three unvaccinated patients acquired poliomyelitis abroad. In the Netherlands vaccination coverage with quadruple DPT-IPV vaccine is very high. The strong immunogenicity of inactivated poliovirus vaccine was confirmed in a cohort of children, reflected in age-stratified antibody profiles of the population. Adults born in the pre vaccination era appeared in general protected, but 10-25% of persons born between 1930 and 1945 lacked neutralizing antibodies. Revaccination induced a booster type of antibody response in 75-90% of such persons, indicating immunological memory and protection. Virological studies on adopted children from other countries, patients with indications for viral examination, and river waters showed that the Netherlands was regularly exposed to polio virus (PV), without signs of indigenous transmission. Persons found to carry PV or their close contacts had travelled to a PV endemic country. Most of 557 isolates were vaccine-derived, only 8% were wild type viruses. Despite their presence, up to 1992 the well-known susceptibles for PV in the Netherlands were shielded by the herd immunity of the Dutch population.

Global immunization--a medical perspective

The global community is close to achieving universal childhood immunization against a group of important childhood diseases--measles, tuberculosis, diphtheria, pertussis, tetanus and polio. In addition, polio has been targeted for eradication by the year 2000 and neonatal tetanus for elimination by 1995. There are targeted reductions in mortality and cases of measles by the same year. This paper addresses the difficult issue of how optimally to integrate these public health initiatives into local health care practices and beliefs. At the workshop on Global Immunization and Culture I presented the perspective of a physician who has worked with the Expanded Programme on Immunization and has understanding at a global level of the logistics of vaccine delivery. This paper serves as a counterpoint to others at the workshop by raising the question of whether routine vaccine delivery and special eradication efforts can be best carried out with a uniform, technologically based approach rather than extensive adaptation of the program to local conditions and beliefs. The reliance on a largely technological approach to control of these childhood diseases which occur in all societies independent of social behavior is contrasted with efforts to control HIV infection in which social structure and practices predict the occurrence of disease.

Immunity to hepatitis B, poliomyelitis and measles in fully vaccinated aboriginal and Torres Strait Island children

OBJECTIVE

To determine the immunity to hepatitis B, poliomyelitis and measles in fully vaccinated Aboriginal and Torres Strait Island children in north Queensland.

METHODOLOGY

A cross-sectional survey of immunity in a sample of children; 101 fully vaccinated Aboriginal and Torres Strait Island children, with a median age of 24.5 months, from 10 communities in North Queensland participated in this study. The main outcome measures were the prevalence of adequate antibody levels against hepatitis B, poliomyelitis and measles.

RESULTS

Only 54% (95% CI 44-63%) of the children had adequate immunity (> or = 10 m iu/mL) to hepatitis B, and one child had been infected despite vaccination. Although all the children (95% CI 96-100%) had adequate immunity (i.e. neutralizing antibodies at a dilution of > or = 1:8) to poliovirus 2, only 93% (95% CI 86-96%) and 60% (95% CI 50-69%) had adequate immunity to polioviruses 1 and 3, respectively. Nearly all (96%; 95% CI 90-98%) of the children had adequate immunity (i.e. detectable IgG antibody) to measles.

CONCLUSIONS

Although a relatively low proportion of the children had adequate antibody levels against hepatitis B the clinical significance of this observation is uncertain. Further studies are needed to determine whether fully vaccinated Torres Strait Island children have been adequately protected and whether they require a booster dose of hepatitis B vaccine. A substantial proportion of fully vaccinated Aboriginal and Torres Strait Island children are inadequately protected against poliomyelitis, and therefore any such child with acute flaccid paralysis should be investigated fully for poliomyelitis. Vaccinated Aboriginal and Torres Strait Island children are well protected against measles, as are other Australian children.

Isolation of epidemic poliovirus from sewage during the 1992-3 type 3 outbreak in The Netherlands

To examine the extent of wild poliovirus circulation during the 1992-3 epidemic in the Netherlands caused by poliovirus type 3, 269 samples from sewage pipelines at 120 locations were examined for the presence of poliovirus. The epidemic virus strain was found in 23 samples, all from locations inside the risk area which contained communities that refuse vaccination for religious reasons. By sewage investigation, the wildtype virus was shown to be present in the early phase of the epidemic at two locations, one week before patients were reported from that area. The wild type 3 poliovirus was also detected retrospectively in a river water sample collected for other reasons three weeks before notification of the first poliomyelitis case, at a site a few kilometres upstream the home village of this patient. Oral poliovirus vaccine (OPV) virus was found at 28 locations inside or at the border of the risk area. Trivalent OPV was offered to unvaccinated or incompletely-vaccinated persons living in this region as part of the measures to control the epidemic.

Diagnostic tests for poliovirus infection: a comparison of neutralization and immunofluorescence for the identification and typing of stool isolates

Neutralization and indirect immunofluorescence were compared for the identification and serotyping of poliovirus. Indirect immunofluorescence was highly concordant with neutralization and offers a more rapid procedure for identification and characterization of poliovirus strains.

Identification of enteroviruses by indirect immunofluorescence using monoclonal antibodies

BACKGROUND

Serum neutralization (Nt) is used most often to type enterovirus isolates, but it is labor-intensive, expensive, and supplies of reference antisera for Nt are limited. Alternative methods of enterovirus typing are needed.

OBJECTIVES

To investigate the use of indirect immunofluorescence (IFA) with commercially available monoclonal antibodies (MAbs) as an alternative to Nt for the identification of enteroviruses.

STUDY DESIGN

Two MAb blends (one for coxsackie B viruses and one for echoviruses 4, 6, 9, 11, 30, and 34) and a coxsackie A9 MAb were used to screen 465 clinical isolates over a period of two years. Virus isolates which tested positive with one of the blends were typed with the individual MAbs of the respective blend. Individual MAbs for polioviruses 1, 2, and 3 acquired late in the study were used to screen 45 viral isolates.

RESULTS

The antibodies identified 251/465 (54%) of the total number of isolates tested. IFA results for 451 of 465 viral isolates were in agreement with conventional identification methods. The sensitivity of the IFA screen using the MAb blends and coxsackie A9 MAb was 93% and the specificity was 99%. Thirteen discrepant isolates were negative by IFA, with twelve positive by Nt for echovirus 30 and one isolate positive by Nt for coxsackie A9. The remaining discrepant isolate was positive by IFA for both coxsackie A9 and coxsackie B5, but positive by Nt for coxsackie A9 only.

CONCLUSIONS

IFA is highly specific for the identification of enteroviruses, but may not be sensitive enough to identify all strains within an enterovirus type. Procedures which utilize an IFA screen and confirm final results by Nt decrease turnaround time and reduce the number of cell culture tubes required for the identification of each enterovirus isolate.

Poliomyelitis outbreak in an unvaccinated community in The Netherlands, 1992-93

An outbreak of poliomyelitis occurred in the Netherlands between September, 1992, and February, 1993, after 14 years without endemic cases. The outbreak was due to poliovirus type 3 and involved 71 patients, of whom 2 died and 59 had paralysis. The patients were aged between 10 days and 61 years (median 18 years). None of the patients had been vaccinated, and all but 1 belonged to a socially and geographically clustered group of people who refuse vaccination for religious reasons. Control measures were taken within 5 days of notification of the first patient and included a wide offer of vaccination with the trivalent oral poliovirus vaccine to the population at risk. Sequence analysis of the viral genome showed closest similarity (96.7%) with a strain isolated in India in 1992, indicating that the virus probably originates from the Indian subcontinent. The difference, however, is still too large to assume direct import. Extensive outbreak investigation at schools, in the environment, at virus diagnostic laboratories, and in the general population showed no evidence of widespread circulation of the epidemic virus outside the groups at risk and area where these groups live. As in the previous outbreak in 1978, the general population, including the majority of unvaccinated people who live dispersed in the population, seemed to be well-protected against poliomyelitis.

Update on childhood immunizations

OBJECTIVE

To provide an overview of childhood immunizations with emphasis in new recommendations, as well as recent vaccine developments and special populations.

DATA SOURCES

English language literature identified via a MEDLINE search. Additional references were obtained from cited references.

STUDY SELECTION AND DATA EXTRACTION

Original articles, reviews, and official publications were used to obtain the most accurate data on safety and efficacy of available pediatric vaccines, as well as current recommendations for their use.

DATA SYNTHESIS

Immunizations have been an area of vigorous research for several years. New vaccines have been developed by improving older products to maximize immunogenicity and minimize adverse effects. Some of these novel vaccines, like the Haemophilus influenzae type b conjugate vaccines (HibCV), have already contributed significantly to the prevention of diseases in childhood. New recommendations have been issued to help speed this process. Adverse effects of routine immunizations are generally mild and transient.

CONCLUSIONS

The development of new effective and safe vaccines for children is an important step in the global eradication of contagious diseases. A new generation of combination vaccines has started with the combination of the diphtheria-tetanus-pertussis vaccine and HibCV. Some other combined products are yet to come that would eventually make immunization schedules more cost-effective and improve compliance rates. Our colleagues in the community and in the ambulatory care setting must actively participate in the implementation of vaccination programs and provide education to parents regarding all aspects of the immunization process.

Quest for life-long protection by vaccination

Life-long protection from disease through immunization can be accomplished through individual or community protection. Individual protection is the goal for vaccination against diseases that have inanimate or animal reservoirs or that pose risks for certain populations. Community protection is the goal for vaccination against diseases that are transmitted only from human to human. Community protection afforded by childhood vaccines has been highly successful against measles, rubella, mumps, and polio. However, outbreaks of measles, rubella, and mumps continue to occur, primarily because of inadequate immunization of children under age 2. Simplification of vaccination regimens, provision of incentives to care providers and parents, and increased access to care should improve vaccination rates in the United States. Better protection requires better use of available vaccines. Eradication of disease through vaccination is the ultimate goal of community protection. Elimination of the infectious agent is the most effective means of achieving life-long protection. The World Health Organization's (WHO) smallpox eradication campaign eliminated a serious disease as well as the need for a vaccine with frequent and severe adverse reactions. The discontinuation of smallpox vaccination in the United States has produced a savings of over $3 billion. Polio has been targeted by WHO for eradication by the year 2000. The eradication of polio and the elimination of the need for polio vaccination in the United States should result in a savings of $110 million per year in vaccine costs alone. Strong United States support is crucial for WHO to reach its goal. Any of the vaccine-preventable childhood virus diseases could be eradicated with sufficient national and international will. Measles and hepatitis B should be high priorities. The ultimate goal of vaccination is life-long protection of all individuals. Any disease of sufficient public health importance to warrant routine vaccination is of sufficient importance to warrant eradication wherever judged to be possible.

The desired field-performance characteristics of new improved vaccines for the developing world

Although the vaccination initiatives undertaken during the past decade are the cornerstones for protecting the world's children and helping to ensure their survival and development, the vaccines currently being employed may become obstacles for further disease reduction or eradication. Their characteristics complicate or increase the burden on health care infrastructures to maintain or expand vaccine delivery systems. This paper examines an experience with the vaccine technologies that currently are being used by immunization programs in developing countries, illustrating the field problems and obstacles associated with their use. It discusses the advantages and benefits that would accrue if new or improved, heat-stable, multi-antigen vaccines that require only one or two, preferably oral, doses were to become available.

The thermostability of vaccines. Technologies for improving the thermostability of the oral poliovirus vaccine

Technologies that promise to enhance the stability of vaccines are likely to be determined by the product-specific physical structure and biological functions of the specific vaccine immunogens. Research may define the extent to which the stability of oral poliovirus vaccine may be improved by the addition of certain antiviral components that bind to the poliovirus capsid or by the application of novel drying technologies.

Comparison of enhanced potency inactivated poliovirus vaccine (EIPV) versus standard oral poliovirus vaccine (OPV) in Thai infants

Enhanced potency inactivated poliovirus vaccine (EIPV), combined with diphtheria-tetanus-pertussis (DTP) vaccine, was compared with oral poliovirus vaccine (OPV) regarding immunogenicity in Thai infants, vaccinated at 2, 4 and 6 months of age. EIPV induced significantly higher seroconversion rates than OPV to all 3 poliovirus types after the second and third immunization. After 3 doses of each vaccine, at 7 months of age, all infants receiving EIPV proved seropositive for poliovirus type 1, type 2 and type 3 neutralizing antibodies, whereas of those receiving OPV, 9% remained seronegative (titre < 1:4) for type 1 (p = 0.0042) and 11% for type 3 (p = 0.0013). All participating children were given an additional dose of OPV at the age of 9 months and tested again at 12 months of age. At that point, virtually all infants had poliovirus neutralizing antibodies, but the geometric mean titres to each poliovirus type were significantly higher in the vaccinees who had received EIPV. It is concluded that the greater immunogenicity of EIPV vis-à-vis 3 doses of OPV may be biologically significant for protection against poliovirus types 1 and 3 in countries where cases of poliomyelitis occur in young children. These findings warrant considering EIPV, alone or in combination with OPV, for an immunization programme in Thailand and similar countries in the future.

Pediatric immunizations

The record of disease prevention in children is an impressive testament to our universal immunization program. However, these successes are being threatened by rates of vaccination in some areas of the country that are substantially less than those seen in the developing world. Unless the pediatric immunization rates are improved, epidemics of other vaccine-preventable diseases will recur, as evidenced by the measles outbreaks. Although the tools needed for disease prevention are available, the means for their delivery are lacking. It is the obligation of us all to immunize the nation's children.