Development of inactivated poliovirus vaccine derived from Sabin strains

Dose-sparing effect of Sabin-derived inactivated polio vaccine produced in Japan by intradermal injection device for rats

The live-attenuated oral polio vaccine has long been used as the standard for polio prevention, but in order to minimize the emergence of pathogenic revertants, the inactivated polio vaccine (IPV), which is administered intramuscularly or subcutaneously, is being increasingly demanded worldwide. However, there is a global shortage of IPV, and its cost is an obstacle in developing countries. Therefore, dose-sparing with intradermal administration of IPV has been investigated. In this study, rats were immunized by intradermal (ID) and intramuscular (IM) administration of Sabin-derived inactivated polio vaccine (sIPV) produced in Japan, and the immune responses were evaluated. The results showed that one-fifth (1/5)-dose of ID administration yielded neutralizing antibody titers comparable to the full-dose IM administration, whereas 1/5-dose of IM administration was less effective than the full dose. Furthermore, a vertical puncture-type ID injection device (Immucise) that was originally developed for humans was modified for rats, resulting in successful and stable ID administration into the thin skin of rats. Based on these results, the ID administration of sIPV using Immucise in clinical use is expected to offer benefits such as reduced amounts of vaccine per dose, cost-effectiveness, and thereby the feasibility of vaccination for more people.

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.

Advax-CpG Adjuvant Provides Antigen Dose-Sparing and Enhanced Immunogenicity for Inactivated Poliomyelitis Virus Vaccines

Global immunization campaigns have resulted in a major decline in the global incidence of polio cases, with wild-type poliovirus remaining endemic in only two countries. Live oral polio vaccine (OPV) played a role in the reduction in polio case numbers; however, the risk of OPV developing into circulating vaccine-derived poliovirus makes it unsuitable for eradication programs. Trivalent inactivated polio virus (TIPV) vaccines which contain formalin-inactivated antigens produced from virulent types 1, 2 and 3 reference polio strains grown in Vero monkey kidney cells have been advocated as a replacement for OPV; however, TIPVs have weak immunogenicity and multiple boosts are required before peak neutralizing titers are reached. This study examined whether the incorporation of the novel polysaccharide adjuvant, Advax-CpG, could boost the immunogenicity of two TIPV vaccines, (i) a commercially available polio vaccine (IPOL^®, Sanofi Pasteur) and (ii) a new TIPV formulation developed by Statens Serum Institut (SSI). Mice were immunized intramuscularly based on recommended vaccine dosage schedules and serum antibody titers were followed for 12 months post-immunization. Advax-CpG significantly enhanced the long-term immunogenicity of both TIPV vaccines and had at least a 10-fold antigen dose-sparing effect. An exception was the poor ability of the SSI TIPV to induce serotype type 1 neutralizing antibodies. Immunization with monovalent IPVs suggested that the low type 1 response to TIPV may be due to antigen competition when the type 1 antigen was co-formulated with the type 2 and 3 antigens. This study provides valuable insights into the complexity of the formulation of multivalent polio vaccines and supports the further development of adjuvanted antigen-sparing TIPV vaccines in the fight to eradicate polio.

Immunogenicity and safety of the inactivated poliomyelitis vaccine made from Sabin strains in a phase IV clinical trial for the vaccination of a large population

As a recently launched novel vaccine used as one of the vaccines for the final eradication of polios worldwide, complete data on the consistency and immunogenicity characteristics of the inactivated poliomyelitis vaccine made from the Sabin strain (sIPV) and its safety in large-scale populations are required to support the future use of this vaccine worldwide. A phase IV clinical trial was conducted to perform an immunogenicity evaluation of lot-to-lot consistency of three commercial batches of sIPV in 1200 infants and to investigate the vaccine's safety on a large-scale in 20,019 infants for active monitoring and 29,683 infants for passive monitoring through the Adverse Event Following Immunization (AEFI) reporting system in China. In the immunogenicity evaluation, the average seroconversion rates for type I, type II and type III of the three groups were 99.83%, 98.93% and 99.44%, respectively. No differences in the seroconversion rate and the GMT ratios were noted in the pair-to-pair comparisons. In the large-scale safety evaluation, most adverse reactions occurred 0-30 days after the first doses, and the common local and systemic reactions were similar to those in the phase III clinical trial, with low incidence in both activated and passive monitoring. In conclusion, sIPV exhibits good lot-to-lot consistency and safety in large-scale populations; thus, it is qualified to serve as one of the vaccines for use in eradicating all wild and vaccine-derived polioviruses worldwide in the near future. Clinic Trial Registration. NCT04224519 and NCT04220515.

Development of an Enterovirus 71 Vaccine Efficacy Test Using Human Scavenger Receptor B2 Transgenic Mice

Enterovirus 71 (EV71) is a causative agent of hand-foot-mouth disease, and it sometimes causes severe neurological disease. Development of effective vaccines and animal models to evaluate vaccine candidates are needed. However, the animal models currently used for vaccine efficacy testing, monkeys and neonatal mice, have economic, ethical, and practical drawbacks. In addition, EV71 strains prepared for lethal challenge often develop decreased virulence during propagation in cell culture. To overcome these problems, we used a mouse model expressing human scavenger receptor B2 (hSCARB2) that showed lifelong susceptibility to EV71. We selected virulent EV71 strains belonging to the subgenogroups B4, B5, C1, C2, and C4 and propagated them using a culture method for EV71 without an apparent reduction in virulence. Here, we describe a novel EV71 vaccine efficacy test based on these hSCARB2 transgenic (Tg) mice and these virulent viruses. Adult Tg mice were immunized subcutaneously with formalin-inactivated EV71. The vaccine elicited sufficient levels of neutralizing antibodies in the immunized mice. The mice were subjected to lethal challenge with virulent viruses via intravenous injection. Survival, clinical signs, and body weight changes were observed for 2 weeks. Most immunized mice survived without clinical signs or histopathological lesions. The viral replication in immunized mice was much lower than that in nonimmunized mice. Mice immunized with the EV71 vaccine were only partially protected against lethal challenge with coxsackievirus A16. These results indicate that this new model is useful for in vivo EV71 vaccine efficacy testing.IMPORTANCE The development of new vaccines for EV71 relies on the availability of small animal models suitable for in vivo efficacy testing. Monkeys and neonatal mice have been used, but the use of these animals has several drawbacks, including high costs, limited susceptibility, and poor experimental reproducibility. In addition, the related ethical issues are considerable. The new efficacy test based on hSCARB2 Tg mice and virulent EV71 strains propagated in genetically modified cell lines presented here can overcome these disadvantages and is expected to accelerate the development of new EV71 vaccines.

An inactivated poliovirus vaccine using Sabin strains produced on the serum-free PER.C6® cell culture platform is immunogenic and safe in a non-human primate model

Background

The World Health Organization recommends the development of affordable next-generation inactivated poliovirus vaccines (IPV) using attenuated poliovirus Sabin strains. Previously, we introduced a novel PER.C6® cell culture platform, which allows for high yield production of an affordable trivalent Sabin IPV vaccine.

Methods

Immunogenicity and safety of this novel PER.C6®-based Sabin-IPV (sIPV) was assessed in rats and non-human primates (NHPs). NHPs received one of four different dose dilutions vaccine according to current human schedule (three prime-immunizations and one boost immunization). For comparison, NHPs received commercially available reference Salk IPV or sIPV.

Results

Dose-dependent immunogenicity and good tolerability was observed for the PER.C6®-based sIPV formulations in rats and NHPs. In NHPs, the lowest tested dose that induced anti-Sabin virus-neutralizing antibody titers that were non-inferior to commercial sIPV after three immunizations was 5-7.5-25 D-antigen units for type 1, 2 and 3 respectively.

Discussion

PER.C6®-based sIPV induced comparable immunogenicity to commercial Salk IPV and sIPV vaccines in NHPs. Together with the absence of any preclinical safety signals, these data warrant further testing in clinical trials. sIPV produced on the PER.C6® cell platform could be one solution to the need for an affordable and immunogenic IPV to achieve and maintain global polio eradication.

Evaluation of the use of various rat strains for immunogenic potency tests of Sabin-derived inactivated polio vaccines

Slc:Wistar rats have been the only strain used in Japan for purpose of evaluating a national reference vaccine for the Sabin-derived inactivated polio vaccine (sIPV) and the immunogenicity of sIPV-containing products. However, following the discovery that the Slc:Wistar strain was genetically related to the Fischer 344 strain, other "real" Wistar strains, such as Crlj:WI, that are available worldwide were tested in terms of their usefulness in evaluating the immunogenicity of the past and current lots of a national reference vaccine. The response of the Crlj:WI rats against the serotype 1 of sIPV was comparable to that of the Slc:Wistar rats, while the Crlj:WI rats exhibited a higher level of response against the serotypes 2 and 3. The immunogenic potency units of a national reference vaccine determined using the Slc:Wistar rats were reproduced on tests using the Crlj:WI rats. These results indicate that a titer of the neutralizing antibody obtained in response to a given dose of sIPV cannot be directly compared between these two rat strains, but that, more importantly, the potency units are almost equivalent for the two rat strains.

Concomitant administration of diphtheria, tetanus, acellular pertussis and inactivated poliovirus vaccine derived from Sabin strains (DTaP-sIPV) with pentavalent rotavirus vaccine in Japanese infants

Rotavirus is the leading cause of severe acute gastroenteritis in infants and young children. Most children are infected with rotavirus, and the health and economic burdens of rotavirus gastroenteritis on healthcare systems and families are considerable. In 2012 pentavalent rotavirus vaccine (RV5) and diphtheria, tetanus, acellular pertussis and inactivated poliovirus vaccine derived from Sabin strains (DTaP-sIPV) were licensed in Japan. We examined the immunogenicity and safety of DTaP-sIPV when administrated concomitantly with RV5 in Japanese infants. A total of 192 infants 6 to 11 weeks of age randomized to Group 1 (N = 96) received DTaP-sIPV and RV5 concomitantly, and Group 2 (N = 96) received DTaP-sIPV and RV5 separately. Antibody titer to diphtheria toxin, pertussis antigens (PT and FHA), tetanus toxin, and poliovirus type 1, 2, and 3 were measured at 4 to 6 weeks following 3-doses of DTaP-sIPV. Seroprotection rates for all components of DTaP-sIPV were 100% in both groups, and the geometric mean titers for DTaP-sIPV in Group 1 were comparable to Group 2. Incidence of systemic AEs (including diarrhea, vomiting, fever, and nasopharyngitis) were lower in Group 1 than in Group 2. All vaccine-related AEs were mild or moderate in intensity. There were no vaccine-related serious AEs, no deaths, and no cases of intussusception during the study. Concomitant administration of DTaP-sIPV and RV5 induced satisfactory immune responses to DTaP-sIPV and acceptable safety profile. The administration of DTaP-sIPV given concomitantly with RV5 is expected to facilitate compliance with the vaccination schedule and improve vaccine coverage in Japanese infants.

Development and introduction of inactivated poliovirus vaccines derived from Sabin strains in Japan

During the endgame of global polio eradication, the universal introduction of inactivated poliovirus vaccines is urgently required to reduce the risk of vaccine-associated paralytic poliomyelitis and polio outbreaks due to wild and vaccine-derived polioviruses. In particular, the development of inactivated poliovirus vaccines (IPVs) derived from the attenuated Sabin strains is considered to be a highly favorable option for the production of novel IPV that reduce the risk of facility-acquired transmission of poliovirus to the communities. In Japan, Sabin-derived IPVs (sIPVs) have been developed and introduced for routine immunization in November 2012. They are the first licensed sIPVs in the world. Consequently, trivalent oral poliovirus vaccine was used for polio control in Japan for more than half a century but has now been removed from the list of vaccines licensed for routine immunization. This paper reviews the development, introduction, characterization, and global status of IPV derived from attenuated Sabin strains.

A national reference for inactivated polio vaccine derived from Sabin strains in Japan

As one aspect of its campaign to eradicate poliomyelitis, the World Health Organization (WHO) has encouraged development of the inactivated polio vaccine (IPV) derived from the Sabin strains (sIPV) as an option for an affordable polio vaccine, especially in low-income countries. The Japan Poliomyelitis Research Institute (JPRI) inactivated three serotypes of the Sabin strains and made sIPV preparations, including serotypes 1, 2 and 3 D-antigens in the ratio of 3:100:100. The National Institute of Infectious Diseases, Japan, assessed the immunogenic stability of these sIPV preparations in a rat potency test, according to an evaluation method recommended by the WHO. The immunogenicity of the three serotypes was maintained for at least 4 years when properly stored under -70°C. Based on these data, the sIPV preparations made by JPRI have been approved as national reference vaccines by the Japanese national control authority and used for the quality control of the tetracomponent sIPV-containing diphtheria-tetanus-acellular pertussis combination vaccines that were licensed for a routine polio immunization in Japan.

Innovative IPV from attenuated Sabin poliovirus or newly designed alternative seed strains

This article gives an overview of the patent literature related to innovative inactivated polio vaccine (i-IPV) based on using Sabin poliovirus strains and newly developed alternative recombinant poliovirus strains. This innovative approach for IPV manufacturing is considered to attribute to the requirement for affordable IPV in the post-polio-eradication era, which is on the horizon. Although IPV is a well-established vaccine, the number of patent applications in this field was seen to have significantly increased in the past decade. Currently, regular IPV appears to be too expensive for universal use. Future affordability may be achieved by using alternative cell lines, alternative virus seed strains, improved and optimized processes, dose sparing, or the use of adjuvants. A relatively short-term option to achieve cost-price reduction is to work on regular IPV, using wild-type poliovirus strains, or on Sabin-IPV, based on using attenuated poliovirus strains. This price reduction can be achieved by introducing efficiency in processing. There are also multiple opportunities to work on dose sparing, for example, by using adjuvants or fractional doses. Renewed interest in this field was clearly reflected in the number and diversity of patent applications. In a later stage, several innovative approaches may become even more attractive, for example the use of recombinant virus strains or even a totally synthetic vaccine. Currently, such work is mainly carried out by research institutes and universities and therefore clinical data are not available.

Dynamic profiles of neutralizing antibody responses elicited in rhesus monkeys immunized with a combined tetravalent DTaP-Sabin IPV candidate vaccine

The World Health Organization has recommended that a Sabin inactivated polio vaccine (IPV) should gradually and synchronously replace oral polio vaccines for routine immunizations because its benefits in eliminating vaccine-associated paralytic poliomyelitis have been reported in different phases of clinical trials. It is also considered important to explore new tetravalent diphtheria, tetanus, and acellular pertussis-Sabin IPV (DTaP-sIPV) candidate vaccines for possible use in developing countries. In this study, the immunogenicity of a combined tetravalent DTaP-sIPV candidate vaccine was investigated in primates by evaluating the neutralizing antibody responses it induced. The dynamic profiles of the antibody responses to each of the separate antigenic components and serotypes of Sabin IPV were determined and their corresponding geometric mean titers were similar to those generated by the tetravalent diphtheria, tetanus, and acellular pertussis-conventional IPV (DTaP-cIPV), the tetravalent diphtheria, tetanus, and acellular pertussis (DTaP), and Sabin IPV vaccines in the control groups. This implies that protective immunogenic effects are conferred by this combined tetravalent formulation.

National choices related to inactivated poliovirus vaccine, innovation and the endgame of global polio eradication

Achieving the goal of a world free of poliomyelitis still requires significant effort. Although polio immunization represents a mature area, the polio endgame will require new tools and strategies, particularly as national and global health leaders coordinate the cessation of all three serotypes of oral poliovirus vaccine and increasingly adopt inactivated poliovirus vaccine (IPV). Poliovirus epidemiology and the global options for managing polioviruses continue to evolve, along with our understanding and appreciation of the resources needed and the risks that require management. Based on insights from modeling, we offer some perspective on the current status of plans and opportunities to achieve and maintain a world free of wild polioviruses and to successfully implement oral poliovirus vaccine cessation. IPV costs and potential wastage will represent an important consideration for national policy makers. Innovations may reduce future IPV costs, but the world urgently needs lower-cost IPV options.

Priming after a fractional dose of inactivated poliovirus vaccine

BACKGROUND

To reduce the costs of maintaining a poliovirus immunization base in low-income areas, we assessed the extent of priming immune responses after the administration of inactivated poliovirus vaccine (IPV).

METHODS

We compared the immunogenicity and reactogenicity of a fractional dose of IPV (one fifth of a full dose) administered intradermally with a full dose administered intramuscularly in Cuban infants at the ages of 4 and 8 months. Blood was collected from infants at the ages of 4 months, 8 months, 8 months 7 days, and 8 months 30 days to assess single-dose seroconversion, single-dose priming of immune responses, and two-dose seroconversion. Specimens were tested with a neutralization assay.

RESULTS

A total of 320 infants underwent randomization, and 310 infants (96.9%) fulfilled the study requirements. In the group receiving the first fractional dose of IPV, seroconversion to poliovirus types 1, 2, and 3 occurred in 16.6%, 47.1%, and 14.7% of participants, respectively, as compared with 46.6%, 62.8%, and 32.0% in the group receiving the first full dose of IPV (P<0.008 for all comparisons). A priming immune response to poliovirus types 1, 2, and 3 occurred in 90.8%, 94.0%, and 89.6% of participants, respectively, in the group receiving the fractional dose as compared with 97.6%, 98.3%, and 98.1% in the group receiving the full dose (P=0.01 for the comparison with type 3). After the administration of the second dose of IPV in the group receiving fractional doses, cumulative two-dose seroconversion to poliovirus types 1, 2, and 3 occurred in 93.6%, 98.1%, and 93.0% of participants, respectively, as compared with 100.0%, 100.0%, and 99.4% in the group receiving the full dose (P<0.006 for the comparisons of types 1 and 3). The group receiving intradermal injections had the greatest number of adverse events, most of which were minor in intensity and none of which had serious consequences.

CONCLUSIONS

This evaluation shows that vaccinating infants with a single fractional dose of IPV can induce priming and seroconversion in more than 90% of immunized infants. (Funded by the World Health Organization and the Pan American Health Organization; Australian New Zealand Clinical Trials Registry number, ACTRN12610001046099.).

History of polio vaccination

Poliomyelitis is an acute paralytic disease caused by three poliovirus (PV) serotypes. Less than 1% of PV infections result in acute flaccid paralysis. The disease was controlled using the formalin-inactivated Salk polio vaccine (IPV) and the Sabin oral polio vaccine (OPV). Global poliomyelitis eradication was proposed in 1988 by the World Health Organization to its member states. The strategic plan established the activities required for polio eradication, certification for regions, OPV cessation phase and post-OPV phase. OPV is the vaccine of choice for the poliomyelitis eradication program because it induces both a systemic and mucosal immune response. The major risks of OPV vaccination are the appearance of Vaccine-Associated Paralytic Poliomyelitis cases (VAPP) and the emergence of Vaccine Derived Polioviruses strains. The supplementary immunization with monovalent strains of OPV type 1 or type 3 or with a new bivalent oral polio vaccine bOPV (containing type 1 and type 3 PV) has been introduced in those regions where the virus has been difficult to control. Most countries have switched the schedule of vaccination by using IPV instead of OPV because it poses no risk of vaccine-related disease. Until 2008, poliomyelitis was controlled in Romania, an Eastern European country, predominantly using OPV. The alternative vaccination schedule (IPV/OPV) was implemented starting in September 2008, while beginning in 2009, the vaccination was IPV only. The risk of VAPP will disappear worldwide with the cessation of use of OPV. The immunization for polio must be maintained for at least 5 to 10 years using IPV.

The polio-eradication programme and issues of the end game

Poliovirus causes paralytic poliomyelitis, an ancient disease of humans that became a major public-health issue in the 20th century. The primary site of infection is the gut, where virus replication is entirely harmless; the two very effective vaccines developed in the 1950s (oral polio vaccine, or OPV, and inactivated polio vaccine, or IPV) induce humoral immunity, which prevents viraemic spread and disease. The success of vaccination in middle-income and developing countries encouraged the World Health Organization to commit itself to an eradication programme, which has made great advances. The features of the infection, including its largely silent nature and the ability of the live vaccine (OPV) to evolve and change in vaccine recipients and their contacts, make eradication particularly challenging. Understanding the pathogenesis and virology of the infection is of major significance as the programme reaches its conclusion.

Inactivated polio vaccine development for technology transfer using attenuated Sabin poliovirus strains to shift from Salk-IPV to Sabin-IPV

Industrial-scale inactivated polio vaccine (IPV) production dates back to the 1960s when at the Rijks Instituut voor de Volksgezondheid (RIV) in Bilthoven a process was developed based on micro-carrier technology and primary monkey kidney cells. This technology was freely shared with several pharmaceutical companies and institutes worldwide. In this contribution, the history of one of the first cell-culture based large-scale biological production processes is summarized. Also, recent developments and the anticipated upcoming shift from regular IPV to Sabin-IPV are presented. Responding to a call by the World Health Organization (WHO) for new polio vaccines, the development of Sabin-IPV was continued, after demonstrating proof of principle in the 1990s, at the Netherlands Vaccine Institute (NVI). Development of Sabin-IPV plays an important role in the WHO polio eradication strategy as biocontainment will be critical in the post-OPV cessation period. The use of attenuated Sabin strains instead of wild-type Salk polio strains will provide additional safety during vaccine production. Initially, the Sabin-IPV production process will be based on the scale-down model of the current, and well-established, Salk-IPV process. In parallel to clinical trial material production, process development, optimization and formulation research is being carried out to further optimize the process and reduce cost per dose. Also, results will be shown from large-scale (to prepare for future technology transfer) generation of Master- and Working virus seedlots, and clinical trial material (for phase I studies) production. Finally, the planned technology transfer to vaccine manufacturers in low and middle-income countries is discussed.

Fractional doses of inactivated poliovirus vaccine in Oman

BACKGROUND

We conducted a clinical trial of fractional doses of inactivated poliovirus vaccine administered to infants in Oman, in order to evaluate strategies for making the vaccine affordable for use in developing countries.

METHODS

We compared fractional doses of inactivated poliovirus vaccine (0.1 ml, representing one fifth of a full dose) given intradermally with the use of a needle-free jet injector device, with full doses of vaccine given intramuscularly, with respect to immunogenicity and reactogenicity. Infants were randomly assigned at birth to receive either a fractional dose or a full dose of inactivated poliovirus vaccine at 2, 4, and 6 months. We also administered a challenge dose of monovalent type 1 oral poliovirus vaccine at 7 months and collected stool samples before and 7 days after administration of the challenge dose.

RESULTS

A total of 400 infants were randomized, of whom 373 (93.2%) fulfilled the study requirements. No significant baseline differences between the groups were detected. Thirty days after completion of the three-dose schedule, the rates of seroconversion to types 1, 2, and 3 poliovirus were 97.3%, 95.7%, and 97.9%, respectively, in the fractional-dose group, as compared with 100% seroconversion to all serotypes in the full-dose group (P=0.01 for the comparison with respect to type 2 poliovirus; results with respect to types 1 and 3 poliovirus were not significant). The median titers were significantly lower in the fractional-dose group than in the full-dose group (P<0.001 for all three poliovirus serotypes). At 7 months, 74.8% of the infants in the fractional-dose group and 63.1% of those in full-dose group excreted type 1 poliovirus (P=0.03). Between birth and 7 months, 42 hospitalizations were reported, all related to infectious causes, anemia, or falls, with no significant difference between vaccination groups.

CONCLUSIONS

These data show that fractional doses of inactivated poliovirus vaccine administered intradermally at 2, 4, and 6 months, as compared with full doses of inactivated poliovirus vaccine given intramuscularly on the same schedule, induce similar levels of seroconversion but significantly lower titers. (Current Controlled Trials number, ISRCTN17418767.)

Optimal vaccine stockpile design for an eradicated disease: application to polio

Eradication of a disease promises significant health and financial benefits. Preserving those benefits, hopefully in perpetuity, requires preparing for the possibility that the causal agent could re-emerge (unintentionally or intentionally). In the case of a vaccine-preventable disease, creation and planning for the use of a vaccine stockpile becomes a primary concern. Doing so requires consideration of the dynamics at different levels, including the stockpile supply chain and transmission of the causal agent. This paper develops a mathematical framework for determining the optimal management of a vaccine stockpile over time. We apply the framework to the polio vaccine stockpile for the post-eradication era and present examples of solutions to one possible framing of the optimization problem. We use the framework to discuss issues relevant to the development and use of the polio vaccine stockpile, including capacity constraints, production and filling delays, risks associated with the stockpile, dynamics and uncertainty of vaccine needs, issues of funding, location, and serotype dependent behavior, and the implications of likely changes over time that might occur. This framework serves as a helpful context for discussions and analyses related to the process of designing and maintaining a stockpile for an eradicated disease.

New generation of inactivated poliovirus vaccines for universal immunization after eradication of poliomyelitis

Twenty years of global polio eradication efforts may soon eliminate the transmission of wild-type poliovirus. However, new information that has been learned about poliovirus, as well as the political realities of a modern world, demand that universal immunity against poliomyelitis be maintained, even after wild-type poliovirus is eradicated. Although 2 excellent vaccines have proven to be highly effective in the past, neither the live-attenuated vaccine nor the currently used inactivated vaccine are optimal for use in the posteradication era. Therefore, concerted efforts are urgently needed to develop a new generation of vaccine that is risk-free and affordable and can be produced on a global scale. Here, we discuss the desired properties of a vaccine and methods to create a new polio vaccine.

Antigenic characterization of a formalin-inactivated poliovirus vaccine derived from live-attenuated Sabin strains

A candidate inactivated poliovirus vaccine derived from live-attenuated Sabin strains (sIPV), which are used in the oral poliovirus vaccine (OPV), was prepared in a large-production scale. The modification of viral antigenic epitopes during the formalin inactivation process was investigated by capture ELISA assays using type-specific and antigenic site-specific monoclonal antibodies (MoAbs). The major antigenic site 1 was modified during the formalin inactivation of Sabin 1. Antigenic sites 1-3 were slightly modified during the formalin inactivation of Sabin 2 strain. Sites 1 and 3 were altered on inactivated Sabin 3 virus. These alterations were different to those shown by wild-type Saukett strain, used in conventional IPV (cIPV). It has been previously reported that type 1 sIPV showed higher immunogenicity to type 1 cIPV whereas types 2 and 3 sIPV induced lower level of immunogenicity than their cIPV counterparts. Our results suggest that the differences in epitope structure after formalin inactivation may account, at least in part, for the observed differences in immunogenicity between Sabin and wild-type inactivated poliovaccines.