New purified Vero-cell vaccine prevents rabies in patients bitten by rabid animals

Safety of purified Vero cell rabies vaccine manufactured in Pakistan: A comparative analysis of intradermal and intramuscular routes

BACKGROUND

Rabies vaccines are conventionally given via the intramuscular (IM) route; however, switching the route of administration from IM to intradermal (ID) without affecting efficacy can be advantageous in terms of cost, dosing, and time. Hence, it is indispensable to evaluate its safety along different routes. This study was carried out to ascertain the frequency of adverse drug events (ADEs) and associated factors, as well as to compare safety based on the IM and ID routes.

METHODS

A prospective observational study was carried out on 184 individuals with rabies exposure. The vaccination schedules for post-exposure prophylaxis (PEP) included 0.2 milliliter (ml) of purified Vero cell rabies vaccine (PVRV) administered ID at two different sites with 0.1ml each on days 0, 3, and 7 in first group (3-dose regimen ID) and 0.5 ml administered IM on days 0, 3, 7, 14, and 28 in the second group (5-dose regimen IM). The safety of the vaccines was determined by reviewing ADEs during physical examinations and follow-up. ADEs were characterized by local and systemic effects.

RESULTS

Of the total, 99 (53.80%) patients reported ADEs. Those who reported local and systemic ADEs were 80 (43.48%) and 59 (32.06%), respectively, while simultaneous occurrence was reported in 40 (40.40%) patients. The most frequent local ADE 76 (41.30%) reported was pain followed by erythema 18 (9.78%). Additionally, fever was in highest proportion 25 (13.59%) for systemic effects, followed by headache 15 (8.15%). The patients reported with ADEs by the IM and ID routes was comparable (p > 0.05). Similarly, both local and systemic effects were also comparable (p > 0.05).

CONCLUSION

Half of the study participants reported ADEs. Almost similar proportions of local and systemic effects were observed. Likewise, the ADEs recorded were comparable for both routes. PVRV carries very low safety concerns with either route for administration.

A recombinant rabies virus chimera expressing the DC-targeting molecular MAB2560 shows enhanced vaccine immunogenicity through activation of dendritic cells

BACKGROUND

Rabies, caused by the rabies virus (RABV), is an ancient and neglected zoonotic disease posing a large public health threat to humans and animals in developing countries. Immunization of animals with a rabies vaccine is the most effective way to control the epidemic and the occurrence of the disease in humans. Therefore, the development of cost-effective and efficient rabies vaccines is urgently needed. The activation of dendritic cells (DCs) is known to play an important role in improving the host immune response induced by rabies vaccines.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we constructed a recombinant virus, rCVS11-MAB2560, based on the reverse genetic system of the RABV CVS11 strain. The MAB2560 protein (a DC-targeting molecular) was chimeric expressed on the surface of the viral particles to help target and activate the DCs when this virus was used as inactivated vaccine. Our results demonstrated that inactivated rCVS11-MAB2560 was able to promote the recruitment and/or proliferation of DC cells, T cells and B cells in mice, and induce good immune memory after two immunizations. Moreover, the inactivated recombinant virus rCVS11-MAB2560 could produce higher levels of virus-neutralizing antibodies (VNAs) in both mice and dogs more quickly than rCVS11 post immunization.

CONCLUSIONS/SIGNIFICANCE

In summary, the recombinant virus rCVS11-MAB2560 chimeric-expressing the molecular adjuvant MAB2560 can stimulate high levels of humoral and cellular immune responses in vivo and can be used as an effective inactivated rabies vaccine candidate.

Investigating the Interaction between Negative Strand RNA Viruses and Their Hosts for Enhanced Vaccine Development and Production

The current pandemic has highlighted the ever-increasing risk of human to human spread of zoonotic pathogens. A number of medically-relevant zoonotic pathogens are negative-strand RNA viruses (NSVs). NSVs are derived from different virus families. Examples like Ebola are known for causing severe symptoms and high mortality rates. Some, like influenza, are known for their ease of person-to-person transmission and lack of pre-existing immunity, enabling rapid spread across many countries around the globe. Containment of outbreaks of NSVs can be difficult owing to their unpredictability and the absence of effective control measures, such as vaccines and antiviral therapeutics. In addition, there remains a lack of essential knowledge of the host–pathogen response that are induced by NSVs, particularly of the immune responses that provide protection. Vaccines are the most effective method for preventing infectious diseases. In fact, in the event of a pandemic, appropriate vaccine design and speed of vaccine supply is the most critical factor in protecting the population, as vaccination is the only sustainable defense. Vaccines need to be safe, efficient, and cost-effective, which is influenced by our understanding of the host–pathogen interface. Additionally, some of the major challenges of vaccines are the establishment of a long-lasting immunity offering cross protection to emerging strains. Although many NSVs are controlled through immunisations, for some, vaccine design has failed or efficacy has proven unreliable. The key behind designing a successful vaccine is understanding the host–pathogen interaction and the host immune response towards NSVs. In this paper, we review the recent research in vaccine design against NSVs and explore the immune responses induced by these viruses. The generation of a robust and integrated approach to development capability and vaccine manufacture can collaboratively support the management of outbreaking NSV disease health risks.

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.

The role of vaccination in rabies prevention

Rabies vaccines have evolved from the first crude nerve tissue vaccines developed by Louis Pasteur and his colleagues in 1885. Currently, safe and efficacious rabies vaccines for humans and animals are produced in several cell culture systems with 10 vaccine regimens recommended by WHO and/or ACIP for pre-exposure and post-exposure prophylaxis in humans. Rabies vaccines are a critical component in the strategy to reduce the dog rabies, the cause of 98% of all global human rabies deaths. However, eliminating rabies in the reservoir animal species is not possible without an intersectoral approach including collaboration between animal and human health experts. There is an urgent need to establish national risk assessment systems in regions where surveillance is limited to non-existent.

Failures of post-exposure rabies prophylaxis

Rabies remains a public health problem in many emerging countries. Virtually all is known that should enable us to eliminate this scourge by controlling the disease in canine populations and by diligent provision of WHO recommended post-exposure prophylaxis (PEP). Nevertheless, post-exposure prophylaxis failures do occur. Most common failures are due to deviations from WHO management recommendations and lack of essential biologicals. True failures, where all was done according to WHO recommendations, are fortunately extremely rare. Presented are seven such deaths. Other examples of common management deviations that resulted in deaths are also shown.

Immunogenicity and effectiveness of post-exposure rabies prophylaxis with a new chromatographically purified Vero-cell rabies vaccine (CPRV): a two-stage randomised clinical trial in the Philippines

Recent improvements in chromatographic purification procedures have made it possible to develop a new chromatographically purified rabies vaccine (CPRV) by further purifying the current rabies vaccine prepared from Vero-cell culture (PVRV) (Verorab; Pasteur Merieux Connaught). The immunogenicity and effectiveness of post-exposure rabies prophylaxis with this new vaccine were evaluated in a two-stage clinical trial conducted in the Philippines. In both study stages. post-exposure treatment consisted of five injections of vaccine [(D)ays 0, 3, 7, 14, 28], together with a dose of rabies immunoglobulin (RIG) of equine or human origin on D0. In stage 1, 231 subjects with low-risk rabies exposure (WHO category I or II), and who had a negative ERIG skin test, were treated with either CPRV (n = 114) or PVRV (n = 117). By D14, all subjects in each group had achieved rabies antibody titres over ten times that recommended by the WHO as indicating seroconversion (> or = 0.5 IU/ml). The kinetics of the immune response to vaccination were very similar in the two groups, and at D28, the immunogenicity of CPRV was equivalent to that of PVRV (one-sided equivalence test). Following these positive results, 132 subjects with severe rabies exposure were included in the second stage of this trial. All were scheduled to receive four vaccine doses with CPRV. After D14, only those 57 patients with confirmed rabies exposure (animal with positive FA test) and seven patients for whom rabies exposure could not be excluded (animal lost or not tested) completed the treatment and were followed for one year to assess survival. After 1 year, 62 patients treated for confirmed or possible severe rabies exposure had been examined and were still alive. Two patients contacted by letter and telephone confirmed good health 7 and 16 months after exposure. No severe local or systemic reactions were reported in either stage of the study, and no treatment-related serious adverse event occurred. This two-stage clinical trial attests to the safety and satisfactory immunogenicity of CPRV in post-exposure rabies treatment, and confirms the effectiveness of a new rabies vaccine in patients with severe confirmed exposure.

Safety and efficacy of purified Vero cell rabies vaccine given intramuscularly and intradermally. (Results of a prospective randomized trial)

OBJECTIVES

To determine adverse reactions as a result of pre- and post-exposure rabies vaccination, using the conventional intramuscular, and reduced dose intradermal regimens and purified Vero cell rabies vaccine.

DESIGN

A prospective and randomized study of patients exposed to rabies and of subjects in need of pre-exposure rabies vaccination.

SETTING

A metropolitan rabies control center in a canine rabies endemic country.

PATIENTS

1198 subjects were recruited between May, 1994 and March, 1996. They were divided into four groups. Patients with suspected or proven rabies exposures were given the vaccine intramuscularly using the conventional regimen, or intradermally using the World Health Organization approved Thai Red Cross schedule. Human or equine rabies immune globulin was administered where indicated. Pre-exposure and post-exposure vaccine recipients were divided randomly into two groups each and given the vaccine either by the intramuscular or intradermal schedules.

MEASUREMENTS

All local and systemic adverse reactions were recorded and statistically analyzed.

RESULTS

Pruritus at injection sites was the only significant local reaction. It was more common in the intradermal groups. Low-grade fever, the only significant adverse systemic event, was more common in the intramuscular groups and was noted in 8% of all subjects. Eighty-four patients bitten by proven rabid animals were found to be alive and well 3 years later. Forty-four of these had received the intramuscular and 40 the intradermal postexposure regimens with human or equine immune globulin injected into wounds on the first day of treatment.

CONCLUSIONS

Purified Vero cell rabies vaccine is safe, carries a very low adverse reaction rate and is effective in preventing rabies in severely exposed subjects when used with human or equine rabies immune globulin.

Randomised feasibility trial of pre-exposure rabies vaccination with DTP-IPV in infants

BACKGROUND

Pre-exposure vaccination against rabies generally simplifies treatment and could be especially beneficial to children in countries where the disease is enzootic. We studied the feasibility of administering to infants pre-exposure rabies vaccination with combined diphtheria, tetanus, whole-cell pertussis, and inactivated poliomyelitis vaccine (DTP-IPV).

METHODS

84 Vietnamese infants were randomly assigned to groups that received three doses of DTP-IPV vaccine at 2, 3, and 4 months of age alone (n = 43) or with two doses of purified Vero cell rabies vaccine (PVRV) at 2 and 4 months (n = 41). The safety and immunogenicity data of the groups were compared.

FINDINGS

All infants in both groups developed protective antibody concentrations against diphtheria, tetanus, pertussis, and polio. All infants who received the PVRV vaccine developed protective antibody concentrations against rabies. No serious adverse effects were reported, nor did systemic reactions differ between groups.

INTERPRETATION

Administration of PVRV with DTP-IPV proved safe, and elicited what are presumed to be protective antibody concentrations to all antigens in all 41 infants. Confirmation of these results could lead to integration of pre-exposure rabies vaccination into Expanded Programme on Immunisation (EPI) sessions in selected countries where rabies is enzootic.

Postexposure prophylaxis for rabies with antiserum and intradermal vaccination

The Thai Red Cross intradermal postexposure rabies treatment schedule was prospectively assessed in 100 Thai patients severely bitten by proven rabid animals. It consists of 0.1 ml of purified Vero cell rabies vaccine containing more than 2.5 IU of rabies antigen per 0.5 ml of reconstituted vaccine given intradermally at two sites on days 0, 3, and 7, followed by one 0.1 ml injection on days 30 and 90. The commercial vaccine used had an antigen content of 3.17 IU per 0.5 ml ampoule. Purified equine or human rabies immuno-globulin was also given on day 0 to patients with severe exposures. As much of the immunoglobulin as possible was infiltrated around the wounds. All patients were followed for 1 year post exposure. There were no deaths; the efficacy of the regimen was 100%. Antibody titre determination in a randomly selected subgroup showed seroconversion in all 10 patients.

Adverse effects of equine rabies immune gobulin

Following a recently published prospective study of 485 recipients of equine rabies immune globulin (ERIG) manufactured by Pasteur Vaccins (Paris), this paper reports a study of 323 postexposure rabies patients receiving ERIG manufactured by the Swiss Vaccine and Serum Institute (Berna). It is concluded that there may be significant differences in adverse reaction rates, reflecting differing manufacturing or purification processes and protein content. Further studies of different ERIG products and of different lots of the same product are needed while ERIG remains an essential component of postexposure rabies treatment in developing countries.

Acceptability and efficacy of purified vero-cell rabies vaccine in Thai children exposed to rabies

A field trial of purified vero-cell tissue culture rabies vaccine (PVRV) was carried out, and 566 children under 15 years of age were studied. Of these 309 (54.6%) had been exposed to laboratory proven rabid animals. Rabies immune globulin (RIG) was given to 47 children with severe exposures. The vaccine was given by the conventional six-dose intramuscular route to 467 patients (82.5%). The remaining 99 victims (17.5%) were given vaccine by the multiple site intradermal route using a schedule of 0.1 ml at two sites on days 0, three and seven, and at one site on days 30 and 90. Adequate follow-up was achieved in 100% of the cases with proven exposure to rabid animals at three months, and in 94.1% at one year. The overall follow-up rate for the entire group was 91.1% at the end of one year, and all patients traced were alive and healthy. The incidence of minor adverse reactions to PVRV was equal to that of other tissue culture rabies vaccines. Regional lymphadenopathy and itching at the injection sites were significantly more common in the group receiving intradermal vaccine than in those who received vaccine by the intramuscular route.

A high rate of neurological complications following Semple anti-rabies vaccine

A fatal case of encephalitis due to Semple (phenolized sheep-brain) anti-rabies vaccine prompted a search for neurological complications among 722 recipients of 2 vaccine batches administered in Bangkok, Thailand in June and July 1984. A review of all patients admitted with neurological symptoms from June through August 1984 to the 5 major teaching hospitals in Bangkok found 6 cases (0.83%), including the index case, who had received the vaccine. Rabies infection was ruled out in all 6 cases. 4 patients had meningitis, and 2 had meningo-encephalitis. Only the index case was fatal; the other patients recovered without neurological sequelae. The rate of neurological complications after receiving Semple vaccine was therefore a minimum of 8.31 cases per 1000 persons vaccinated (1:120). This complication rate was about 25 times higher than the overall complication rate of 0.33 per 1000 (1:3018) determined from 14 previous reports. The fatality rate was 1.39 per 1000 (1:722), about 15 times higher than the rate of 0.09 per 1000 (1:10805) calculated from the previous studies. It is urgent to find economically feasible alternatives to Semple vaccine.