Detection of diphtheritic polyneuropathy by acute flaccid paralysis surveillance, India

Diphtheritic polyneuropathy is a vaccine-preventable illness caused by exotoxin-producing strains of Corynebacterium diphtheriae. We present a retrospective convenience case series of 15 children (6 girls) <15 years of age (mean age 5.2 years, case-fatality rate 53%, and 1 additional case-patient who was ventilator dependent at the time of last follow-up; median follow-up period 60 days) with signs and symptoms suggestive of diphtheritic polyneuropathy. All cases were identified through national acute flaccid paralysis surveillance, which was designed to detect poliomyelitis in India during 2002–2008. We also report data on detection of diphtheritic polyneuropathy compared with other causes of acute flaccid paralysis identified by this surveillance system.

Poliovirus vaccination options for achieving eradication and securing the endgame

In 1988, the World Health Assembly resolved to globally eradicate poliomyelitis. As part of a four-pronged strategy with establishment of enhanced surveillance, institution of national immunization days, strengthening routine immunization, and carrying-out mopping-up activities, oral poliovirus vaccine (OPV) was selected as the vaccine-of-choice for eradication. Massive OPV use decreased the number of polio-endemic countries from >125 countries in 1988 to only 3 in 2012 and led to a >99.9% decrease in polio incidence in the corresponding period. In this communication, we will discuss polio vaccination options to accelerate eradication, to mitigate the risks during the planned withdrawal of type 2 OPV, and to secure eradication for future generations.

Review and assessment of poliovirus immunity and transmission: synthesis of knowledge gaps and identification of research needs

With the intensifying global efforts to eradicate wild polioviruses, policymakers face complex decisions related to achieving eradication and managing posteradication risks. These decisions and the expanding use of inactivated poliovirus vaccine (IPV) trigger renewed interest in poliovirus immunity, particularly the role of mucosal immunity in the transmission of polioviruses. Sustained high population immunity to poliovirus transmission represents a key prerequisite to eradication, but poliovirus immunity and transmission remain poorly understood despite decades of studies. In April 2010, the U.S. Centers for Disease Control and Prevention convened an international group of experts on poliovirus immunology and virology to review the literature relevant for modeling poliovirus transmission, develop a consensus about related uncertainties, and identify research needs. This article synthesizes the quantitative assessments and research needs identified during the process. Limitations in the evidence from oral poliovirus vaccine (OPV) challenge studies and other relevant data led to differences in expert assessments, indicating the need for additional data, particularly in several priority areas for research: (1) the ability of IPV-induced immunity to prevent or reduce excretion and affect transmission, (2) the impact of waning immunity on the probability and extent of poliovirus excretion, (3) the relationship between the concentration of poliovirus excreted and infectiousness to others in different settings, and (4) the relative role of fecal-oral versus oropharyngeal transmission. This assessment of current knowledge supports the immediate conduct of additional studies to address the gaps.

Expert review on poliovirus immunity and transmission

Successfully managing risks to achieve wild polioviruses (WPVs) eradication and address the complexities of oral poliovirus vaccine (OPV) cessation to stop all cases of paralytic poliomyelitis depends strongly on our collective understanding of poliovirus immunity and transmission. With increased shifting from OPV to inactivated poliovirus vaccine (IPV), numerous risk management choices motivate the need to understand the tradeoffs and uncertainties and to develop models to help inform decisions. The U.S. Centers for Disease Control and Prevention hosted a meeting of international experts in April 2010 to review the available literature relevant to poliovirus immunity and transmission. This expert review evaluates 66 OPV challenge studies and other evidence to support the development of quantitative models of poliovirus transmission and potential outbreaks. This review focuses on characterization of immunity as a function of exposure history in terms of susceptibility to excretion, duration of excretion, and concentration of excreted virus. We also discuss the evidence of waning of host immunity to poliovirus transmission, the relationship between the concentration of poliovirus excreted and infectiousness, the importance of different transmission routes, and the differences in transmissibility between OPV and WPV. We discuss the limitations of the available evidence for use in polio risk models, and conclude that despite the relatively large number of studies on immunity, very limited data exist to directly support quantification of model inputs related to transmission. Given the limitations in the evidence, we identify the need for expert input to derive quantitative model inputs from the existing data.

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.).

Oral and inactivated poliovirus vaccines in the newborn: a review

BACKGROUND

Oral poliovirus vaccine (OPV) remains the vaccine-of-choice for routine immunization and supplemental immunization activities (SIAs) to eradicate poliomyelitis globally. Recent data from India suggested lower than expected immunogenicity of an OPV birth dose, prompting a review of the immunogenicity of OPV or inactivated poliovirus vaccine (IPV) when administered at birth.

METHODS

We evaluated the seroconversion and reported adverse events among infants given a single birth dose (given ≤7 days of life) of OPV or IPV through a systematic review of published articles and conference abstracts from 1959 to 2011 in any language found on PubMed, Google Scholar, or reference lists of selected articles.

RESULTS

25 articles from 13 countries published between 1959 and 2011 documented seroconversion rates in newborns following an OPV dose given within the first seven days of life. There were 10 studies that measured seroconversion rates between 4 and 8 weeks of a single birth dose of TOPV, using an umbilical cord blood draw at the time of birth to establish baseline antibody levels. The percentage of newborns who seroconverted at 8 weeks range from 6-42% for poliovirus type 1, 2-63% for type 2, and 1-35% for type 3. For mOPV type 1, seroconversion ranged from 10 to 76%; mOPV type 3, the range was 12-58%; and for the one study reporting bOPV, it was 20% for type 1 and 7% for type 3. There were four studies of IPV in newborns with a seroconversion rate of 8-100% for serotype 1, 15-100% for serotype 2, and 15-94% for serotype 3, measured at 4-6 weeks of life. No serious adverse events related to newborn OPV or IPV dosing were reported, including no cases of acute flaccid paralysis.

CONCLUSIONS

There is great variability of the immunogenicity of a birth dose of OPV for reasons largely unknown. Our review confirms the utility of a birth dose of OPV, particularly in countries where early induction of polio immunity is imperative. IPV has higher seroconversion rates in newborns and may be a superior choice in countries which can afford IPV, but there have been few studies of an IPV dose for newborns.

Waning intestinal immunity after vaccination with oral poliovirus vaccines in India

BACKGROUND

The eradication of wild-type polioviruses in areas with efficient fecal-oral transmission relies on intestinal mucosal immunity induced by oral poliovirus vaccine (OPV). Mucosal immunity is thought to wane over time but the rate of loss of protection has not been examined.

METHODS

We examined the degree and duration of intestinal mucosal immunity in India by measuring the prevalence of vaccine poliovirus in stool samples collected 4-28 days after a "challenge" dose of OPV among 47 574 children with acute flaccid paralysis reported during 2005-2009.

RESULTS

Previous vaccination with OPV was protective against excretion of vaccine poliovirus after challenge, but the odds of excretion increased significantly with the time since the child was last exposed to an immunization activity (odds ratio, 1.39 [95% confidence interval .99-1.97], 2.04 [1.28-3.25], and 1.31 [1.00-1.70] comparing ≥6 months with 1 month ago for serotypes 1, 2, and 3, respectively). Vaccine administered during the high season for enterovirus infections (April-September) was significantly less likely to result in excretion, especially in northern states (odds ratio, 0.57 [95% confidence interval, .50-.65], 0.58 [.41-.81], and 0.48 [.40-.57] for serotypes 1, 2, and 3).

CONCLUSIONS

Infection with OPV (vaccine "take") is highly seasonal in India and results in intestinal mucosal immunity that appears to wane significantly within a year of vaccination.

Guillain-Barré Syndrome in India: population-based validation of the Brighton criteria

OBJECTIVE

Case definitions of GBS were recently developed in response to the 2009 H1N1 vaccination programme but have undergone limited field testing. We validate the sensitivity of the Brighton Working Group case definitions for Guillain-Barré Syndrome (GBS) using a population-based cohort in India.

METHODS

The National Polio Surveillance Unit of India actively collects all cases of acute flaccid paralysis (AFP) in children <15 years old, including cases of GBS. Cases of GBS with available cerebrospinal fluid (CSF) and nerve conduction studies (NCS) results, neurological examination, clinical history, and exclusion of related diagnoses were selected (2002-2003). Relevant data were abstracted and entered into a central database. Sensitivity of the Brighton GBS criteria for level 3 of diagnostic certainty which requires no clinical laboratory testing, level 2 which employs CSF or NCS, and level 1 which employs both, were calculated.

RESULTS

79 cases of GBS (mean age 6.5 years, range 4.0-14.5; 39% female) met the case definition. GBS cases were ascending (79%), symmetrical (85%), and bilateral (100%); involving lower extremity hypotonia (86%) and weakness (100%), upper extremity hypotonia (62%) and weakness (80%), areflexia/hyporeflexia (88%), respiratory muscles (22%), bulbar muscles (22%), and cranial nerves (13%). Four limbs were involved in 80% of cases. Mean time to maximal weakness was 5.2 days (range 0.5-30 days) with nadir GBS disability scores of 3 (7%), 4 (67%), 5 (15%), 6 (10%), or unclear (1%). CSF (mean time to lumbar puncture 29 days) was normal in 29% with cytoalbuminologic dissociation in 65% (mean protein 105 mg/dL, range 10-1000; mean cell count 11/μL, range 0-220, n=4 with >50 cells/μL). Significant improvement occurred in 73% whereas death (9%) occurred 6-29 days after sensorimotor symptom onset. The majority of cases (86%) fulfilled Brighton level 3, level 2 (84%), and level 1 (62%) of diagnostic certainty.

CONCLUSION

The diagnosis of GBS can be made using Brighton Working Group criteria in India with moderate to high sensitivity. Brighton Working Group case definitions are a plausible standard for capturing a majority of cases of GBS in field operations in low income settings during AFP surveillance.

Immunogenicity of bivalent types 1 and 3 oral poliovirus vaccine: a randomised, double-blind, controlled trial

BACKGROUND

Poliovirus types 1 and 3 co-circulate in poliomyelitis-endemic countries. We aimed to assess the immunogenicity of a novel bivalent types 1 and 3 oral poliovirus vaccine (bOPV).

METHODS

We did a randomised, double-blind, controlled trial to assess the superiority of monovalent type 2 OPV (mOPV2), mOPV3, or bOPV over trivalent OPV (tOPV), and the non-inferiority of bivalent vaccine compared with mOPV1 and mOPV3. The study was done at three centres in India between Aug 6, 2008, and Dec 26, 2008. Random allocation was done by permuted blocks of ten. The primary outcome was seroconversion after one monovalent or bivalent vaccine dose compared with a dose of trivalent vaccine at birth. The secondary endpoints were seroconversion after two vaccine doses compared with after two trivalent vaccine doses and cumulative two-dose seroconversion. Parents or guardians and study investigators were masked to treatment allocation. Because of multiple comparisons, we defined p≤0·01 as statistically significant. This trial is registered with Current Controlled Trials, ISRCTN 64725429.

RESULTS

900 newborn babies were randomly assigned to one of five vaccine groups (about 180 patients per group); of these 70 (8%) discontinued, leaving 830 (92%) for analysis. After the first dose, seroconversion to poliovirus type 1 was 20% for both mOPV1 (33 of 168) and bOPV (32 of 159) compared with 15% for tOPV (25 of 168; p>0·01), to poliovirus type 2 was 21% (35 of 170) for mOPV2 compared with 25% (42 of 168) for tOPV (p>0·01), and to poliovirus type 3 was 12% (20 of 165) for mOPV3 and 7% (11 of 159) for bOPV compared with 4% (7 of 168) for tOPV (mOPV3 vs tOPV p=0·01; bOPV vs tOPV; p>0·01). Cumulative two-dose seroconversion to poliovirus type 1 was 90% (151 of 168) for mOPV1 and 86% (136 of 159) for bOPV compared with 63% (106 of 168) for tOPV (p<0·0001), to poliovirus type 2 was 90% (153 of 170) for mOPV2 compared with 91% (153 of 168) for tOPV (p>0·01), and to poliovirus type 3 was 84% (138 of 165) for mOPV3 and 74% (117 of 159) for bOPV compared with 52% (87 of 168) for tOPV (p<0·0001). The vaccines were well tolerated. 19 serious adverse events occurred, including one death; however, these events were not attributed to the trial interventions.

INTERPRETATION

The findings show the superiority of bOPV compared with tOPV, and the non-inferiority of bOPV compared with mOPV1 and mOPV3.

FUNDING

GAVI Alliance, World Health Organization, and Panacea Biotec.

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.)

Asymptomatic wild-type poliovirus infection in India among children with previous oral poliovirus vaccination

BACKGROUND

Mucosal immunity induced by oral poliovirus vaccine (OPV) is imperfect and potentially allows immunized individuals to participate in asymptomatic wild-type poliovirus transmission in settings with efficient fecal-oral transmission of infection.

METHODS

We examined the extent of asymptomatic wild-type poliovirus transmission in India by measuring the prevalence of virus in stool samples obtained from 14,005 healthy children who were in contact with 2761 individuals with suspected poliomyelitis reported during the period 2003-2008.

RESULTS

Wild-type poliovirus serotypes 1 and 3 were isolated from the stool samples of 103 (0.74%) and 104 (0.74%) healthy contacts, respectively. Among contacts of individuals with laboratory-confirmed poliomyelitis, 27 (12.7%) of 213 and 29 (13.9%) of 209 had serotypes 1 and 3, respectively, isolated from their stool samples. The odds ratio of excreting serotype 1 wild-type poliovirus was 0.13 (95% confidence interval, 0.02-0.87) among healthy children reporting 6 doses of OPV, compared with children reporting 0-2 doses. However, two-thirds of healthy children who excreted this virus reported >or=6 doses, and the prevalence of this virus did not decrease with age over the sampled range.

CONCLUSIONS

Although OPV is protective against infection with poliovirus, the majority of healthy contacts who excreted wild-type poliovirus were well vaccinated. This is consistent with a potential role for OPV-vaccinated children in continued wild-type poliovirus transmission and requires further study.

Mucosal immunity after vaccination with monovalent and trivalent oral poliovirus vaccine in India

BACKGROUND

Persistent wild-poliovirus transmission, particularly in India, has raised questions about the degree of mucosal immunity induced by oral poliovirus vaccine (OPV) in tropical countries.

METHODS

Excretion of vaccine poliovirus after challenge with OPV was measured in stool samples collected from children identified by the acute flaccid paralysis surveillance program in India during 2005-2007. The effectiveness of trivalent and monovalent OPV against excretion of each poliovirus type was estimated.

RESULTS

Vaccine poliovirus was isolated from 4994 (5.2%) of 96,641 children with 2 stool samples. The relative odds of excreting challenge poliovirus among children with 5 reported previous doses of trivalent OPV compared with 0 previous doses was 0.24 (95% confidence interval [CI], 0.12-0.45), 0.08 (95% CI, 0.04-0.14), and 0.40 (95% CI, 0.19-0.85) for serotypes 1, 2, and 3, respectively, but the relative odds increased to 0.62 (95% CI, 0.44-0.88), 0.44 (95% CI, 0.20-0.99), and 0.66 (95% CI, 0.41-1.06), respectively, in the northern states of Uttar Pradesh and Bihar. In these 2 states, the relative odds of excretion of serotype 1 was 0.32 (95% CI, 0.26-0.41) after 5 doses of type 1 monovalent OPV.

CONCLUSIONS

The mucosal immunity induced by OPV in India varies by location, serotype, and vaccine formulation. These findings have implications for global eradication and the potential role played by inactivated vaccine in this setting.

Estimating the extent of vaccine-derived poliovirus infection

Background

Eight outbreaks of paralytic polio attributable to circulating vaccine-derived poliovirus (cVDPV) have highlighted the risks associated with oral poliovirus vaccine (OPV) use in areas of low vaccination coverage and poor hygiene. As the Polio Eradication Initiative enters its final stages, it is important to consider the extent to which these viruses spread under different conditions, so that appropriate strategies can be devised to prevent or respond to future cVDPV outbreaks.

Methods and Findings

This paper examines epidemiological (temporal, geographic, age, vaccine history, social group, ascertainment), and virological (type, genetic diversity, virulence) parameters in order to infer the numbers of individuals likely to have been infected in each of these cVDPV outbreaks, and in association with single acute flaccid paralysis (AFP) cases attributable to VDPVs. Although only 114 virologically-confirmed paralytic cases were identified in the eight cVDPV outbreaks, it is likely that a minimum of hundreds of thousands, and more likely several million individuals were infected during these events, and that many thousands more have been infected by VDPV lineages within outbreaks which have escaped detection.

Conclusions

Our estimates of the extent of cVDPV circulation suggest widespread transmission in some countries, as might be expected from endemic wild poliovirus transmission in these same settings. These methods for inferring extent of infection will be useful in the context of identifying future surveillance needs, planning for OPV cessation and preparing outbreak response plans.

Monovalent type 1 oral poliovirus vaccine in newborns

BACKGROUND

In 1988, the World Health Assembly resolved to eradicate poliomyelitis. Although substantial progress toward this goal has been made, eradication remains elusive. In 2004, the World Health Organization called for the development of a potentially more immunogenic monovalent type 1 oral poliovirus vaccine.

METHODS

We conducted a trial in Egypt to compare the immunogenicity of a newly licensed monovalent type 1 oral poliovirus vaccine with that of a trivalent oral poliovirus vaccine. Subjects were randomly assigned to receive one dose of monovalent type 1 oral poliovirus vaccine or trivalent oral poliovirus vaccine at birth. Thirty days after birth, a single challenge dose of monovalent type 1 oral poliovirus vaccine was administered in all subjects. Shedding of serotype 1 poliovirus was assessed through day 60.

RESULTS

A total of 530 subjects were enrolled, and 421 fulfilled the study requirements. Thirty days after the study vaccines were administered, the rate of seroconversion to type 1 poliovirus was 55.4% in the monovalent-vaccine group, as compared with 32.1% in the trivalent-vaccine group (P<0.001). Among those with a high reciprocal titer of maternally derived antibodies against type 1 poliovirus (>64), 46.0% of the subjects in the monovalent-vaccine group underwent seroconversion, as compared with 21.3% in the trivalent-vaccine group (P<0.001). Seven days after administration of the challenge dose of monovalent type 1 vaccine, a significantly lower proportion of subjects in the monovalent-vaccine group than in the trivalent-vaccine group excreted type 1 poliovirus (25.9% vs. 41.5%, P=0.001). None of the serious adverse events reported were attributed to the trial interventions.

CONCLUSIONS

When given at birth, monovalent type 1 oral poliovirus vaccine is superior to trivalent oral poliovirus vaccine in inducing humoral antibodies against type 1 poliovirus, overcoming high preexisting levels of maternally derived antibodies, and increasing the resistance to excretion of type 1 poliovirus after administration of a challenge dose. (Current Controlled Trials number, ISRCTN76316509.)

Uncertainty and sensitivity analyses of a decision analytic model for posteradication polio risk management

Decision analytic modeling of polio risk management policies after eradication may help inform decisionmakers about the quantitative tradeoffs implied by various options. Given the significant dynamic complexity and uncertainty involving posteradication decisions, this article aims to clarify the structure of a decision analytic model developed to help characterize the risks, costs, and benefits of various options for polio risk management after eradication of wild polioviruses and analyze the implications of different sources of uncertainty. We provide an influence diagram of the model with a description of each component, explore the impact of different assumptions about model inputs, and present probability distributions of model outputs. The results show that choices made about surveillance, response, and containment for different income groups and immunization policies play a major role in the expected final costs and polio cases. While the overall policy implications of the model remain robust to the variations of assumptions and input uncertainty we considered, the analyses suggest the need for policymakers to carefully consider tradeoffs and for further studies to address the most important knowledge gaps.

The risks, costs, and benefits of possible future global policies for managing polioviruses

OBJECTIVES

We assessed the costs, risks, and benefits of possible future major policy decisions on vaccination, surveillance, response plans, and containment following global eradication of wild polioviruses.

METHODS

We developed a decision analytic model to estimate the incremental cost-effectiveness ratios and net benefits of risk management options for polio for the 20-year period and stratified the world according to income level to capture important variability between nations.

RESULTS

For low-, lower-middle-, and upper-middle-income groups currently using oral poliovirus vaccine (OPV), we found that after successful eradication of wild polioviruses, OPV cessation would save both costs and lives when compared with continued use of OPV without supplemental immunization activities. We found cost-effectiveness ratios for switching from OPV to inactivated poliovirus vaccine to be higher (i.e., less desirable) than other health investment opportunities, depending on the actual inactivated poliovirus vaccine costs and assumptions about whether supplemental immunization activities with OPV would continue.

CONCLUSIONS

Eradication promises billions of dollars of net benefits, although global health policy leaders face difficult choices about future policies. Until successful eradication and coordination of posteradication policies, health authorities should continue routine polio vaccination and supplemental immunization activities.