Evaluation of a one week intradermal regimen for rabies post-exposure prophylaxis: results of a randomized, open label, active-controlled trial in healthy adult volunteers in India

Tracking lethal threat: in-depth review of rabies

An infectious disease known as rabies (family Rhabdoviridae, genus Lyssavirus) causes severe damage to mammals' central nervous systems (CNS). This illness has been around for a very long time. The majority of human cases of rabies take place in underdeveloped regions of Africa and Asia. Following viral transmission, the Rhabdovirus enters the peripheral nervous system and proceeds to the CNS, where it targets the encephalon and produces encephalomyelitis. Postbite prophylaxis requires laboratory confirmation of rabies in both people and animals. All warm-blooded animals can transmit the Lyssavirus infection, while the virus can also develop in the cells of cold-blooded animals. In the 21st century, more than 3 billion people are in danger of contracting the rabies virus in more than 100 different nations, resulting in an annual death toll of 50,000-59,000. There are three important elements in handling rabies disease in post exposure prophylaxis (PEP), namely wound care, administration of anti-rabies serum, and anti-rabies vaccine. Social costs include death, lost productivity as a result of early death, illness as a result of vaccination side effects, and the psychological toll that exposure to these deadly diseases has on people. Humans are most frequently exposed to canine rabies, especially youngsters and the poor, and there are few resources available to treat or prevent exposure, making prevention of human rabies challenging.

Preclinical evaluation of performance, safety and usability of VAX-ID®, a novel intradermal injection device

The recent SARS-Cov2 pandemic and mpox health emergency have led to renewed interest in intradermal vaccination due to its dose sparing potential. Indeed, intradermal vaccination is particularly of interest for use in mass vaccination campaigns, pandemic preparedness programs, and/or for vaccines that are expensive or in short supply. Moreover, the rich immune network in the skin makes it an attractive target not only for prophylactic vaccination, but also for therapeutic vaccination, like immunotherapy and (dendritic) cell-based therapies. The aim of the current paper was to provide an overview of preclinical data generated with VAX-ID®, a novel intradermal drug delivery device, to allow assessing it performance, safety and usability. The device can overcome challenges seen with the Mantoux technique whereby the needle needs to be inserted under a shallow angle. Various parameters of VAX-ID® were evaluated, including dead-space volume, dose accuracy, penetration depth & liquid deposit in piglets, as well as usability by healthcare professionals. The device has shown to have a low dead volume and a high dose accuracy. Importantly, the device performed successful injections at a predefined depth into the dermis with a high safety profile as confirmed by visual and histological evaluation in piglets. Moreover, the device was rated as easy to use by healthcare professionals. The combined preclinical performance and usability findings indicate that VAX-ID® can provide reliable, standardized and accurate drug delivery in the dermal layer of the skin with a high ease of use. The device offers a solution for injection of various prophylactic as well as therapeutic vaccines.

Safety and Immunogenicity of a novel three-dose recombinant nanoparticle rabies G protein vaccine administered as simulated post exposure immunization: A randomized, comparator controlled, multicenter, phase III clinical study

BACKGROUND

Rabies vaccines are lifesaving in human post animal exposure. However, the compliance to the complete course of vaccine is found to be only 60%. Hence, there is a need for safe and immunogenic, shorter course vaccine that can enhance the compliance and effectively prevent the disease.

OBJECTIVES

To establish a noninferiority of a novel three-dose recombinant rabies G protein vaccine to be administered as simulated postexposure prophylaxis when compared to five-dose WHO prequalified vaccine for better safety and immunogenicity.

METHODS

A multi-centric, open label, assessor blind, center-specific block randomized, parallel design, phase III clinical study was conducted among 800 subjects. The eligible subjects were randomized in 2:1 ratio for recombinant rabies G protein vaccine and the reference vaccine. Subjects in recombinant rabies G protein vaccine arm received three doses of vaccine on days 0, 3, and 7, while subjects in reference vaccine arm received five doses of WHO prequalified vaccine on days 0, 3, 7, 14, and 28.

RESULTS

The socio-demographic characteristics of the two arms were comparable. About 9.9% subjects in recombinant rabies G protein vaccine arm and 17.2% subjects in reference arm reported adverse events. The sero-protection on day 14 was found to be 99.24% and 97.72% in recombinant rabies G protein vaccine arm and reference vaccine arm respectively and the difference was statistically nonsignificant.

CONCLUSION

The novel three-dose recombinant rabies G protein vaccine administered as simulated postexposure prophylaxis was noninferior to five dose WHO prequalified vaccine in terms of safety and immunogenicity.

A shorter post-exposure prophylaxis regimen for rabies, Pakistan

OBJECTIVE

To assess the cost and effectiveness of the two-site, 1-week, intradermal rabies post-exposure prophylaxis regimen recommended by the World Health Organization (WHO) in 2018.

METHODS

We compared the number of rabies vaccine and rabies immunoglobulin ampoules consumed at The Indus Hospital in Karachi, Pakistan and their cost before and after implementing WHO's 2018 recommendations. In 2017, patients with suspected rabies-infected bites were treated using the two-site, 4-week, Thai Red Cross regimen, which involved administering four rabies vaccine doses intradermally over 4 weeks and infiltrating immunoglobulin into serious wounds, with the remainder injected into a distant muscle. In 2018, patients received three vaccine doses intradermally over 1 week, with a calculated amount of immunoglobulin infiltrated into wounds only. Remaining immunoglobulin was saved for other patients. The survival of patients bitten by apparently rabid dogs was used as a surrogate for effectiveness.

FINDINGS

Despite treating 8.5% more patients in 2018 (5370 patients) than 2017 (4948 patients), 140 fewer ampoules of rabies vaccine and 436 fewer ampoules of rabies immunoglobulin were used, at a cost saving of 4202 United States dollars. Of 56 patients bitten by apparently rabid dogs, 50 were alive at 6-month follow-up. The remaining six patients could not be contacted but did not present to any hospital with rabies.

CONCLUSION

The new regimen was more economical than the two-site, 4-week regimen and was equally effective. This regimen is recommended for preventing rabies in countries where the disease is endemic and rabies vaccine and immunoglobulin are in short supply.

Immunogenicity after pre- and post-exposure rabies vaccination: A systematic review and dose-response meta-analysis

BACKGROUND

There are a myriad of vaccine schedules for rabies pre- (PrEP) and post-exposure prophylaxis (PEP) that differ in the number and timedoses, number of visits, length of schedule, and route of administration. The objective of this study was to systematically review the evidence and investigate how thedifferences in schedules influence titres over time.

METHODS

Four databaseswere searched from inception to January 2020 for rabies PrEP and PEP studies. Adose-response meta-analysis was utilised to pool geometric mean titres (GMT) over time. Subgroup analyses by route of administration, age group, and schedule were conducted.

RESULTS

80 studies met the inclusion criteria and contributed with 191 datasets and 12,413 participants. Both intradermal (ID) and intramuscular (IM) PrEP/PEP produce adequate GMTs. Significantly lower GMT levels were achieved in older (>50yrs) compared to younger (<50yrs) participants. Short 1-week schedules were as effective as longer schedules that can take between 3 and 12 weeks to complete.

CONCLUSIONS

Several effective ID and IM schedules were identified, the selection of a schedule should take into account the patient's needs, costs, availability to return for subsequent doses, and the time required to complete the schedule. Older individuals warrant special attention as they develop lower antibody response.

Safety and immunogenicity of SURE RAB™, an inactivated cell culture derived rabies vaccine: A comparative, phase III clinical trial

INTRODUCTION

Rabies is a viral zoonotic disease widespread across the world. In India, various cell culture vaccines are available for pre and post exposure prophylaxis (PEP) but are not sufficient to meet the rising demand. The present study evaluated the safety and immunogenicity of Rabies vaccine Human I.P. (Brand name: SURE RAB™) in PEP and demonstrated its non-inferiority to already approved rabies vaccine (Brand name: VERORAB).

MATERIAL AND METHODS

It was a phase-III randomized, open label, comparative, single centre clinical trial in post exposure subjects. Safety and immunogenicity were evaluated at Day 0, 14 and 45 ± 7 post vaccination. Day 14 serum samples were analyzed by Enzyme Linked Immunesorbent assay (IgG ELISA, Bio-Rad) and Day 0, 14 and 45 ± 7 serum were tested by Rapid Fluorescent Focus Inhibition Test (RFFIT). Paired t-test was applied to compare the results of Rabies virus neutralizing antibody (RVNA). The severity of adverse reactions was measured on a scale of excellent, good, fair and bad; p-value (p < 0.05) was considered as statistically significant.

RESULTS

All the subjects achieved a protective titer value between 0.5 and 9.0 IU/ml by Day 14 tested by ELISA and significant rise in the antibody titer in all the groups when tested after 45 days. Statistically significant p-value (p < 0.001) observed with RFFIT test indicated biological potency of rabies vaccine. Adverse events and safety was comparable statistically between three groups (p ​= ​0.886) and Group I ​+ ​II combined versus Group III (p = 0.495).

CONCLUSION

The study results conclusively demonstrate that SURE RAB™ is comparable to VERORAB in terms of safety and immunogenicity and can be used for PEP in rabies.

Single-visit, 4-site intradermal (ID) rabies vaccination induces robust immune responses 5 years after 1-week, 4-site ID primary post-exposure prophylaxis in the Philippines

BACKGROUND

In a randomized controlled study (NCT01622062) a 1-week, 4-site intradermal (ID, 4-4-4-0-0) post-exposure prophylaxis (PEP) rabies vaccination regimen with purified Vero cell rabies vaccine (PVRV, Verorab®, Sanofi Pasteur), either without (Group 1) or with (Group 2) purified equine rabies immunoglobulin (ERIG), patients in the Philippines achieved seroconversion rates at Day 14 that were non-inferior to that of the updated Thai Red Cross (TRC) 28-day, 2-site (2-2-2-0-2) ID regimen with ERIG (Group 3). Presented here are the annual immunogenicity data up to five years after the last primary dose, and the immunogenicity and safety data following simulated PEP with single-visit, 4-site ID regimen.

METHODS

Rabies virus neutralizing antibodies (RVNA) were determined by rapid fluorescent focus inhibition test (RFFIT). Participants (n = 397) received simulated PEP vaccination ID at Year 5 and RVNAs were assessed at Day 11 post-vaccination.

RESULTS

Seroconversion rates (RVNA titres ≥ 0.5 IU/mL) during annual follow-up remained >95% in Group 1 and were relatively stable at 80-90% in Group 2, but decreased from 80% to 64% in Group 3. RVNA geometric mean titres (GMTs) in Group 1 were consistently higher than in the other two groups, and those in Group 3 were generally lower than in the other two groups. There was a clear anamnestic response to vaccination in all groups, with all participants achieving RVNA titres ≥ 0.5 IU/mL at Day 11 post-simulated PEP booster vaccination. There were no safety concerns raised during annual follow-up and with simulated post-exposure vaccination with PVRV.

CONCLUSION

The shortened, 1-week, 4-site ID regimen with PVRV achieved persistently higher RVNA titres than the updated 2-site TRC regimen, and more participants remained seroprotected up to five years after the last dose of primary immunization. Simulated post-exposure with 4-site ID rapidly induced an anamnestic response indicative of robust protection.

Purified Vero Cell Rabies Vaccine (PVRV, Verorab®): A Systematic Review of Intradermal Use Between 1985 and 2019

The purified Vero cell rabies vaccine (PVRV; Verorab®, Sanofi Pasteur) has been used in rabies prevention since 1985. Evolving rabies vaccination trends, including shorter intradermal (ID) regimens with reduced volume, along with WHO recommendation for ID administration has driven recent ID PVRV regimen assessments. Thus, a consolidated review comparing immunogenicity of PVRV ID regimens during pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP) is timely and beneficial in identifying gaps in current research. A search of seven databases for studies published from 1985 to November 2019 identified 35 studies. PrEP was assessed in 10 studies (n = 926) with 1-3-site, 1-3-visit regimens of up to 3-months duration. Seroconversion (rabies virus neutralizing antibodies [RVNA] ≥ 0.5 IU/mL) rates of 90-100% were reported within weeks, irrespective of regimen, with robust booster responses at 1 year (100% seroconversion rates by day 14 post-booster). However, data are lacking for the current WHO-recommended, 2-site, 1-week ID PrEP regimen. PEP was assessed in 25 studies (n = 2136) across regimens of 1-week to 90-day duration. All ID PEP regimens assessed induced ≥ 99% seroconversion rates (except in HIV participants) by day 14-28. This review confirms ID PVRV suitability for rabies prophylaxis and highlights the heterogeneity of use in the field.

Modelling to inform prophylaxis regimens to prevent human rabies

BACKGROUND

The Strategic Advisory Group of Experts (SAGE) Working Group on rabies vaccines and immunoglobulins was established in 2016 to develop practical and feasible recommendations for prevention of human rabies. To support the SAGE agenda we developed models to compare the relative costs and potential benefits of rabies prevention strategies.

METHODS

We examined Post-Exposure Prophylaxis (PEP) regimens, protocols for administration of Rabies Immunoglobulin (RIG) and inclusion of rabies Pre-Exposure Prophylaxis (PrEP) within the Expanded Programme on Immunization (EPI). For different PEP regimens, clinic throughputs and consumables for vaccine administration, we evaluated the cost per patient treated, costs to patients and potential to treat more patients given limited vaccine availability.

RESULTS

We found that intradermal (ID) vaccination reduces the volume of vaccine used in all settings, is less costly and has potential to mitigate vaccine shortages. Specifically, the abridged 1-week 2-site ID regimen was the most cost-effective PEP regimen, even in settings with low numbers of bite patients presenting to clinics. We found advantages of administering RIG to the wound(s) only, using considerably less product than when the remaining dose is injected intramuscularly distant to the wound(s). We found that PrEP as part of the EPI programme would be substantially more expensive than use of PEP and dog vaccination in prevention of human rabies.

CONCLUSIONS

These modeling insights inform WHO recommendations for use of human rabies vaccines and biologicals. Specifically, the 1-week 2-site ID regimen is recommended as it is less costly and treats many more patients when vaccine is in short supply. If available, RIG should be administered at the wound only. PrEP is highly unlikely to be an efficient use of resources and should therefore only be considered in extreme circumstances, where the incidence of rabies exposures is extremely high.

Intradermal post-exposure rabies vaccination with purified Vero cell rabies vaccine: Comparison of a one-week, 4-site regimen versus updated Thai Red Cross regimen in a randomized non-inferiority trial in the Philippines

BACKGROUND

Rabies post-exposure prophylaxis (PEP) via intradermal (ID) administration is standard practice in Asia. Accumulating evidence suggests that PEP shortened to 3 visits in one week does not adversely affect seroconversion rates or immune memory.

OBJECTIVE

To determine whether the seroconversion rate at Day14 with a 1-week, 4-site (4-4-4-0-0) ID vaccination regimen with or without rabies immunoglobulin (RIG) was non-inferior to the updated Thai Red Cross (TRC) 28-day, 2-site (2-2-2-0-2) ID regimen with RIG during rabies PEP. We also assessed one-year antibody persistence.

METHODS

This phase III, mono-center, open-label, randomized-controlled trial assigned participants aged ≤50 years (n = 600) exposed to suspected rabid animals and sustaining WHO Category II injuries (automatic allocation to G1) or Category III injuries (randomized to G2 or G3) to the following groups (1:1:1 ratio): G1 (n = 200), 1-week 4-site ID regimen with the purified Vero cell rabies vaccine (PVRV; Verorab®) without RIG; G2 (n = 201), 1-week 4-site ID regimen with PVRV, and purified equine rabies immunoglobulin (pERIG); G3 (n = 199), TRC 28-day, 2-site ID regimen with PVRV, and pERIG. Non-inferiority tests compared G1 vs. G3 and G2 vs. G3. Seroconversion rate was the proportion (%) of vaccinees with rabies virus neutralizing antibodies (RVNA) titers ≥0.5 IU/mL measured by rapid fluorescent focus inhibition test.

RESULTS

On Day14, after the third vaccine administration, seroconversion rates were non-inferior in both comparisons and were, respectively, 100%, 99.4%, 98.8% in G1, G2, G3 with a decrease to 97.6%, 89%, 79.8% at Year 1. At Day14, RVNA geometric mean titers were 11.3 IU/mL; 9.89 IU/mL; 6.15 IU/mL, respectively, decreasing to 2.96 IU/mL, 1.37 IU/mL, 0.97 IU/mL at Year1. Safety and tolerability were similar between the three groups.

CONCLUSION

The seroconversion rate at Day 14 with the 1-week 4-site ID regimen, both with and without pERIG, was non-inferior to the reference TRC 28-day 2-site ID regimen with pERIG during rabies PEP with PVRV. ClinicalTrials.gov ID: NCT01622062.

Rabies post-exposure prophylaxis: A systematic review on abridged vaccination schedules and the effect of changing administration routes during a single course

Rabies is a fatal zoonotic disease preventable through timely and adequate post-exposure prophylaxis (PEP) to potentially exposed persons i.e. wound washing and antisepsis, a series of intradermal (ID) or intramuscular (IM) rabies vaccinations, and rabies immunoglobulin in WHO category III exposures. The 2010 WHO position on rabies vaccines recommended PEP schedules requiring up to 5 clinic visits over the course of approximately one month. Abridged schedules with less doses have potential to save costs, increase patient compliance, and thereby improve equitable access to life-saving PEP for at-risk populations. We systematically reviewed new evidence since that considered for the 2010 position paper to evaluate (i) the immunogenicity and effectiveness of PEP schedules of reduced dose and duration; (ii) new evidence on effective PEP protocols for special populations; and (iii) the effect of changing routes of administration (ID or IM) during a single course of PEP. Our search identified a total of 14 relevant studies. The identified studies supported a reduction in dose or duration of rabies PEP schedules. The 1-week, 2-site ID PEP schedule was found to be most advantageous, as it was safe, immunogenic, supported by clinical outcome data and involved the least direct costs (i.e. cost of vaccine) compared to other schedules. To supplement this evidence, as yet unpublished additional data were reviewed to support the strength of the recommendations. Evidence suggests that changes in the rabies vaccine product and/or the route of administration during PEP is possible. Few studies have evaluated PEP schedules in persons with suspect or confirmed rabies exposures. Gaps exist in understanding the safety and immunogenicity of novel PEP schedules in special populations such as infants and immunocompromised individuals. Available data indicate that administering rabies vaccines during pregnancy is safe and effective.

An overview of the immunogenicity and effectiveness of current human rabies vaccines administered by intradermal route

Pre- as well as post-exposure prophylaxis plays an important role in controlling the number of deaths associated with human rabies. Rabies vaccines, classically injected intramuscularly, are now also administered by intradermal (ID) route. Vaccines to be administered by the ID route should meet the same quality, safety and efficacy specifications as vaccines for intramuscular (IM) use. The aim of this paper is to provide information based on publicly available data regarding the ID use of rabies vaccines and to identify potential needs for further analysis of the potency, immunogenicity and effectiveness of rabies vaccines administered by this route. A first literature search, focused on the immunogenicity of rabies vaccines given by ID route, identified 338 publications in the period 1997-2018, 40 of which were included in our analyses. A second search investigating the effectiveness of ID vaccination resulted in 371 hits for the period 2007-2018, of which 13 suitable publications were retained. The immunogenicity of current rabies vaccines was analyzed in 3 ways: proportion of subjects reaching the antibody threshold of 0.5 IU/ml after ID vaccination, relationship between potency and immunogenicity of the vaccine given intradermally, and comparison of antibody responses after IM or ID vaccination. Overall, vaccines administered intradermally were found immunogenic. Post-exposure prophylaxis by ID route appeared at least as immunogenic as by IM regimens. By contrast, ID pre-exposure prophylaxis trended towards lower antibody titers than IM vaccination, but the observation was not associated with any clinical relevance. Vaccine effectiveness was assessed by investigating survival after exposure. Data from more than 30,000 patients who sought rabies post-exposure prophylaxis did not indicate that current vaccines administered by ID route lack efficacy. These results support current recommendations for ID vaccination against rabies. However, published data on ID performance were associated with significant weaknesses that future research should better address.

Evaluating new rabies post-exposure prophylaxis (PEP) regimens or vaccines

The development of human rabies vaccines has evolved dramatically from the first crude nerve tissue vaccine produced then administered in the presence of Louis Pasteur in 1885. New cell culture technology has enabled highly potent and well-tolerated rabies vaccines to be produced that have reduced the volume and number of doses required to save human lives after exposure. However, these highly potent vaccines are still unaffordable to many patients living at risk of exposure on a daily basis. The cost of post-exposure prophylaxis (PEP) is not only related to the direct cost of rabies biologicals and equipment but is also associated with indirect costs that patients incur as a result of travel, loss of work time (income loss), and accommodation over the period of time that a PEP regimen requires to be completed. This paper summarizes the particular criteria that the SAGE Working Group and WHO personnel reviewed as part of the evaluation process for recommending the new one-week intradermal vaccination regimen (2-2-2-0-0) for rabies post-exposure prophylaxis. These criteria included: Cost-effectiveness; evaluation of number of doses; seroconversion after vaccination; efficacy; safety; and patient follow-up.

Post-exposure prophylaxis (PEP) for rabies with purified chick embryo cell vaccine: a systematic literature review and meta-analysis

INTRODUCTION

Fifteen million people each year receive post-exposure prophylaxis (PEP) to prevent rabies, yet the disease remains neglected and highly under-reported.

AREAS COVERED

In this systematic literature review, we assessed the immunogenicity, efficacy, and safety of a purified chick embryo cell-culture rabies vaccine (PCECV) for PEP against rabies by intramuscular (IM) or intradermal (ID) administration. We performed meta-analyses to compare immunogenicity according to the route of vaccine administration, study population, and PEP regimen, such as number of doses, and concomitant rabies immunoglobulin.

EXPERT COMMENTARY

There were 54 estimates of immune responses to vaccination, which showed that in the overall population, after starting PEP with PCECV by the IM or ID route (≥2.5 IU per dose), almost all individuals had rabies virus neutralizing antibody (RVNA) titers above the World Health Organization (WHO) recommended serological threshold for an adequate immune response to vaccination (RVNA ≥0.5 IU/ml by day 14). In the overall population, PCECV had an acceptable safety profile. However, given that there are 59,000 human rabies deaths reported annually, the challenge is to improve access to PCECV for PEP against human rabies.

Shortening intradermal rabies post-exposure prophylaxis regimens to 1 week: Results from a phase III clinical trial in children, adolescents and adults

Background

This phase III clinical trial compared the immunogenicity and safety of a purified chick-embryo cell rabies vaccine (PCECV) administered according to a shortened post-exposure prophylaxis (PEP) 4-site/1-week intradermal regimen, compared with the currently recommended 2-site/Thai Red Cross (TRC) regimen.

Methodology/Principal findings

This controlled, open-label, multi-center study (NCT02177032) enrolled healthy individuals ≥1 year of age, randomized into 4 groups to receive intradermal PCECV according to one of the 2 regimens, with or without human rabies immunoglobulin (HRIG) administration at first visit (in adults only). Rabies virus neutralizing antibody (RVNA) concentrations and percentages of participants with RVNA concentrations ≥0.5 IU/mL (considered as adequate concentrations following PEP) were assessed up to day (D) 365 post-first vaccination. Non-inferiority of the 4-site/1-week regimen to the 2-site/TRC regimen was demonstrated if at D49, the lower limit of the 95% confidence interval (CI) for the difference between groups in the percentage of participants with adequate RVNA concentrations was >-5%. Of the 443 participants receiving the 4-site/1-week regimen, 88 adults received HRIG; 442 participants received the 2-site/TRC regimen (88 with HRIG). All participants achieved adequate RVNA concentrations by D14. At D49, the difference in percentage of participants with adequate RVNA concentrations between the 4-site/1-week and the 2-site/TRC groups was -1 (95%CI: -2.4–0.0); thus, non-inferiority was concluded. RVNA geometric mean concentrations were 18 IU/mL in 4-site/1-week groups and 12 IU/mL in 2-site/TRC groups at D14, and subsequently declined in all groups. RVNA concentrations were consistently lower in adults with HRIG administration than in those without. The 2 regimens had similar safety profiles. Of the 15 serious adverse events reported in 4-site/1-week groups and 19 in 2-site/TRC groups, none were vaccination-related.

Significance

The data suggest that the 4-site/1-week regimen might be an alternative to current recommendations, with potential benefits in terms of improved cost-efficiency and compliance to vaccination.

Rabies is a deadly, but vaccine-preventable disease which still causes tens of thousands of deaths yearly, mostly in Asia and Africa. Rabies virus is spread via the saliva of infected mammals to humans, usually through bites or contamination of open wounds. Access to measures like wound cleansing with soap and rabies vaccination immediately after contact with a suspected rabid animal (exposure) can be life-saving. The post-exposure vaccination schedule currently recommended by the World Health Organization for intradermal injection is the Thai Red Cross regimen, requiring 4 clinic visits in one month, with 2 injections given at each visit on days (D) 0 (day of the contact), 3, 7, and 28. In this study, we evaluated the antibody responses and the safety profile of a new shortened schedule, requiring 3 clinic visits and only 1 week to complete, consisting of 4 intradermal injections given at each visit on D0, 3, and 7 (the 4-site/1-week regimen). The study was conducted in the Philippines and Thailand which enrolled 885 healthy volunteers, at least 1 year of age, with no real exposure to rabies. The two schedules induced adequate antibody responses in similar proportion of volunteers at day 49. The vaccine administration according to both schedules was well tolerated.

Diagnostic difficulties in human rabies: A case report and review of the literature

Rabies is a zoonotic disease with the highest fatality rate of any infectious disease. The clinical features of rabies encephalopathy are highly nonspecific at the onset and clinicians from low endemic areas usually face difficulties in recognizing cases during the early stages. The need for establishing a rapid and accurate test to identify rabies during the ante-mortem period is important. However, in actual clinical practice, the latter may remain difficult for various reasons. In human rabies, positively identifying the antigen, antibody or genetic material by various diagnostic methods during the symptomatic period is affected by the unpredictable nature of viremia, levels of antibody immune response of the host, and the virulence of the infecting strain. Also, more advanced testing with greater sensitivity may not be readily available at all centers. Here we describe a case of a young male who was bitten by a rabid dog and developed progressive encephalopathy with a fatal outcome, with negative antibodies in the cerebrospinal fluid (CSF). A review of the literature on the clinical features, diagnostic tests, treatment and prevention of rabies is also presented.

Persistence of Rabies Virus-Neutralizing Antibodies after Vaccination of Rural Population following Vampire Bat Rabies Outbreak in Brazil

BACKGROUND

Animal control measures in Latin America have decreased the incidence of urban human rabies transmitted by dogs and cats; currently most cases of human rabies are transmitted by bats. In 2004-2005, rabies outbreaks in populations living in rural Brazil prompted widespread vaccination of exposed and at-risk populations. More than 3,500 inhabitants of Augusto Correa (Pará State) received either post-exposure (PEP) or pre-exposure (PrEP) prophylaxis. This study evaluated the persistence of rabies virus-neutralizing antibodies (RVNA) annually for 4 years post-vaccination. The aim was to evaluate the impact of rabies PrEP and PEP in a population at risk living in a rural setting to help improve management of vampire bat exposure and provide additional data on the need for booster vaccination against rabies.

METHODOLOGY/PRINCIPAL FINDINGS

This prospective study was conducted in 2007 through 2009 in a population previously vaccinated in 2005; study participants were followed-up annually. An RVNA titer >0.5 International Units (IU)/mL was chosen as the threshold of seroconversion. Participants with titers ≤0.5 IU/mL or Equivalent Units (EU)/mL at enrollment or at subsequent annual visits received booster doses of purified Vero cell rabies vaccine (PVRV). Adherence of the participants from this Amazonian community to the study protocol was excellent, with 428 of the 509 (84%) who attended the first interview in 2007 returning for the final visit in 2009. The long-term RVNA persistence was good, with 85-88.0% of the non-boosted participants evaluated at each yearly follow-up visit remaining seroconverted. Similar RVNA persistence profiles were observed in participants originally given PEP or PrEP in 2005, and the GMT of the study population remained >1 IU/mL 4 years after vaccination. At the end of the study, 51 subjects (11.9% of the interviewed population) had received at least one dose of booster since their vaccination in 2005.

CONCLUSIONS/SIGNIFICANCE

This study and the events preceding it underscore the need for the health authorities in rabies enzootic countries to decide on the best strategies and timing for the introduction of routine rabies PrEP vaccination in affected areas.

Rabies post-exposure prophylaxis for a child with severe allergic reaction to rabies vaccine

Most adverse events (AEs) during the immunization of rabies vaccine were slight, there was little information about the allergic reaction induced by rabies vaccines and had to stop or change the immunization program. Here, we reported a case that a 4-year-old boy had category II exposure to rabies and showed severe allergic reaction after being immunized with lyophilized purified vero cell rabies vaccine (PVRV). After the anti-allergy therapy with hormone, allergy testing indicated medium allergy to egg and milk, and implied the allergic reaction most likely associated with animal-sourced gelatin in lyophilized PVRV. Therefore, a new immunization program with liquid PVRV without stabilizers under the Zegrab regimen (2-1-1) was enrolled at day 7 post-exposure. Although lower than the levels of normal <5 -year population at day 14 and 45, the neutralizing antibody (RVNA) titers of this boy showed adequate protective antibody (≥ 0.5 IU/ml), even after 365 d post-immunization. This study not only highlighted the importance of several types of rabies vaccines co-existing in the market, but also implied the necessary for doctors to fully understand the allergies history of patients prior to immunize rabies vaccine.

Animal Bites and Rabies Prophylaxis in Rural Children: Indian Perspective

A prospective observational study was conducted in a tertiary care hospital to study clinicoepidemiological profile of potentially rabid animal bite cases from rural India. Total of 308 children (median age 6 years) admitted to hospital, were recruited over 1 year and followed up till completion of antirabies vaccine course. Dog was the commonest (77.27%) offending animal. Of the exposures, 66.88% were scratches, 88.96% were unprovoked and 27.27% were categorized as Class III. The median times to wound toileting and reporting to health facility were 1 and 6 h, respectively. Majority received prompt PEP in hospital, and RIG was administered in 34.55% of Class II and 90.48% of Class III exposures. Compared with their older counterparts, children aged <5 years suffered more bites on face and trunk and more Class III exposures. The rabies prophylaxis scenario is encouraging, when compared with earlier studies, but there are gaps to be addressed.

Comparative study on the immunogenicity and safety of a purified chick embryo cell rabies vaccine (PCECV) administered according to two different simulated post exposure intramuscular regimens (Zagreb versus Essen)

Despite availability of effective rabies vaccines, India has the highest global mortality rate for rabies. Low socio-economic communities are most affected due to lack of awareness of the disease and poor compliance to post-exposure prophylactic regimens. Currently, the only approved intramuscular regimen for post-exposure prophylaxis (PEP) against rabies in India is the Essen regimen, which consists of 5 injections administered over 5 separate days in a period of one month. The high number of doses and clinical visits, however, are major reasons for non-compliance, and thus a shorter regimen would be beneficial. In a simulated PEP trial in healthy, adult subjects, this study evaluated whether purified chick embryo cell vaccine (PCECV), administered according to the WHO-recommended 4-dose/3 visit Zagreb vaccination regimen is of equal immunogenicity and safety as the standard Essen regimen in Indian subjects. Two hundred and 50 healthy adults were enrolled and randomized into a Zagreb or Essen group, each receiving PCECV according to their respective regimen. Blood samples were collected on Days 0, 7, 14 and 42 and analyzed using the rapid fluorescent focus inhibition test (RFFIT). By Day 14, all subjects across both groups attained rabies virus neutralizing antibody (RVNA) concentrations of ≥ 0.5IU/ml. The Zagreb regimen was then demonstrated to be immunologically non-inferior to the Essen regimen by Day 14, which was the primary endpoint of the study. No safety issues were noted and the occurrence of adverse events was similar in both groups (17% and 15%, respectively). NCT01365494. CTRI No.: CTRI/2011/07/001857.

Why we can prevent, control and possibly treat – but will not eradicate – rabies

ABSTRACT 

Rabies is an acute, progressive viral encephalitis. Despite historical recognition, millions still remain exposed annually. Most fatalities are of children, although this zoonosis is a vaccine-preventable disease. All developed countries interrupted canine transmission and increasingly, Asian and African communities recognize what Latin Americans demonstrated – dog rabies can be eliminated – by mass application of veterinary vaccines. Realistically, rabies is not a candidate for eradication. Management is lacking for major reservoirs, such as bats. Increasing pre-exposure immunization of individuals at risk, simplification of postexposure schedules, enhancing vaccine delivery by alternative routes, development of less expensive biologics and antiviral drugs, may lessen its impact if applied strategically in a One Health context.

Comparison of safety and immunogenicity of 2 WHO prequalified rabies vaccines administered by one week, 4 site intra dermal regimen (4-4-4-0-0) in animal bite cases

The currently advocated rabies post-exposure prophylaxis regimens are of one month duration with reduced patient compliance. WHO recommended research on shortened vaccination regimens which have a practical and economic advantage over the existing regimens. Hence, the present study was undertaken to assess the safety and immunogenicity of 2 WHO prequalified rabies vaccines administered by one week, 4 site intra dermal regimen (4-4-4-0-0) in animal bite cases. This study was a comparative, open label, phase III, randomized clinical trial conducted at Anti rabies clinic, KIMS Hospital, Bangalore, India. The study was registered in Clinical Trials Registry of India (CTRI) bearing the registration number CTRI/2012/12/003230. Ninety subjects with category II/III animal bites/exposures were enrolled. Equine rabies immunoglobulin was administered to all category III exposures. 0.1 mL of either purified chick embryo cell vaccine (Rabipur) or purified verocell rabies vaccine (Verorab) was administered intradermally into 4 sites on days 0, 3 and 7 to all the study subjects. Serum of subjects collected on day 0, 14, 90 and 365 were analyzed for rabies virus neutralizing antibody (RVNA) concentration. The incidence of ADR in Rabipur and Verorab group was 2.96% and 1.14% respectively. In Rabipur group, geometric mean concentration (95% confidence interval) of RVNA was 14.5 (13.50, 15.57), 11.78 (11.27, 12.31) and 5.95 (5.50, 6.44) IU/mL on days 14, 90 and 365 respectively; In Verorab group geometric mean concentration (95% confidence interval) of RVNA was 14.43 (13.41, 15.53), 11.93 (11.47, 12.40) and 5.67 (5.29, 6.08) IU/mL on days 14, 90 and 365 respectively. In conclusion, Rabipur and Verorab were found to be safe, immunogenic and comparable with each other, when administered using one week, 4 site intradermal regimen (4-4-4-0-0) in animal bite cases.

Assessing safety and immunogenicity of post-exposure prophylaxis following interchangeability of rabies vaccines in humans

Rabies post exposure prophylaxis with cell culture vaccines by either intramuscular route or intradermal route spans over a period of one month. World Health Organization recommends completing post exposure prophylaxis against rabies with the same cell culture or embryonated egg rabies vaccine and with same route of administration and any deviation from this shall be an exception. In the present study, the safety and immunogenicity of rabies post-exposure prophylaxis was studied prospectively in 90 animal bite cases that had interchangeability of rabies vaccines either by route of administration or brand/type and such changes had occurred due to logistical/financial problems. Among them, 47 had change in route of administration from intramuscular to intradermal or vice versa and 43 had change in the brand/type of cell culture rabies vaccine. All of them had category III rabies exposure and received equine rabies immunoglobulin along with the rabies vaccine. None of the study subjects had any adverse reactions. The rabies virus neutralizing antibody titers was assessed by rapid fluorescent focus inhibition test and all the vaccinees had titers ≥0.5 IU per mL on day 14 which is considered as adequate for protection against rabies. Thus, the present study showed that, rabies post-exposure prophylaxis was safe and immunogenic despite changes in the route of administration and brand/type of rabies vaccine.