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

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.

Fractional dose of intradermal compared to intramuscular and subcutaneous vaccination - A systematic review and meta-analysis

BACKGROUND

Vaccine supply shortages are of global concern. We hypothesise that intradermal (ID) immunisation as an alternative to standard routes might augment vaccine supply utilisation without loss of vaccine immunogenicity and efficacy.

METHODS

We conducted a systematic review and meta-analysis searching Medline, Embase and Web of Science databases. Studies were included if: licensed, currently available vaccines were used; fractional dose of ID was compared to IM or SC immunisation; primary immunisation schedules were evaluated; immunogenicity, safety data and/or cost were reported. We calculated risk differences (RD). Studies were included in meta-analysis if: a pre-defined immune correlate of protection was assessed; WHO-recommend schedules and antigen doses were used in the control group; the same schedule was applied to both ID and control groups (PROSPERO registration no. CRD42020151725).

RESULTS

The primary search yielded 5,873 articles, of which 156 articles were included; covering 12 vaccines. Non-inferiority of immunogenicity with 20-60% of antigen used with ID vaccines was demonstrated for influenza (H1N1: RD -0·01; 95% CI -0·02, 0·01; I² = 55%, H2N3: RD 0·00; 95% CI -0·01, 0·01; I² = 0%, B: RD -0·00; 95% CI -0·02, 0·01; I² = 72%), rabies (RD 0·00; 95% CI -0·02, 0·02; I² = 0%), and hepatitis B vaccines (RD -0·01; 95% CI -0·04, 0·02; I² = 20%). Clinical trials on the remaining vaccines yielded promising results, but are scarce.

CONCLUSIONS

There is potential for inoculum/antigen dose-reduction by using ID immunisation as compared to standard routes of administration for some vaccines (e.g. influenza, rabies). When suitable, vaccine trials should include an ID arm.

Immunogenicity and safety of two-visit, intradermal pre-exposure rabies prophylaxis simultaneously administrated with chimeric live-attenuated Japanese encephalitis vaccine in children living in rabies and Japanese encephalitis endemic country

BACKGROUND

Reducing the number of doses required for pre-exposure prophylaxis (PrEP) would make it more feasible and cost-effective to implement in children at the highest risk of rabies exposure in Asia. We studied immune response of 2-site intradermal (ID) injection of rabies vaccine on days 0 and 28 for rabies PrEP simultaneously administrated with live-attenuated Japanese encephalitis chimeric virus vaccine (JE-CV) for children living in endemic area.

RESEARCH DESIGN AND METHODS

Seronegative children (n = 49) aged 12-16 months were randomized 2:1 into two groups: Group A subjects were vaccinated with 0.1-mL ID injection of purified Vero cell rabies vaccine (PVRV), each at two sites on day (D) 0 and D28; Group B subjects were vaccinated with conventional 0.5-mL intramuscular PVRV on D0, D7 and D28. Both groups received one dose of JE-CV subcutaneously on D0 and D365. Rabies virus neutralizing antibody (RVNA) titers were measured on D0, D42 and D365 after vaccination; Japanese Encephalitis (JE) neutralizing antibody titers were determined on D0, D42, D365 and D379.

RESULTS

All children had RVNA ≥ 0.5 IU/mL on D42 (geometric mean titers [GMTs] of RVNA 14.35 IU/mL [Group A] and 14.83 IU/mL [Group B], p > 0.05]). On D365, RVNA GMTs of subjects in group A and B were 1.50 IU/mL and 2.00 IU/mL (p > 0.05), respectively. All children had seroprotection following booster dose of JE-CV. There were no vaccine-related SAEs observed.

CONCLUSION

The 2-site ID PrEP with PVRV on days 0 and 28 co-administrated with JE-CV are safe and immunogenic.

Immunogenicity and safety of WHO-approved TRC-ID regimen with a chromatographically purified Vero cell rabies vaccine with or without rabies immunoglobulin in children

INTRODUCTION

Children are at risk of rabies exposure in many Asian countries. The safety and immunogenicity profile of the WHO-approved two-site intradermal Thai Red Cross regimen (modified TRC-ID regimen; 2-2-2-0-2) with a new chromatographically purified Vero-cell rabies vaccine (CPRV) is lacking. Area covered: We studied the safety and immunogenicity of the TRC-ID regimen with a new CPRV in non-immunized Thai children with possible or proven rabies exposure. Thirty-nine seronegative patients (age range 2-14 years) with rabies exposure (WHO categories II or III) received two 0.1-mL intradermal doses of CPRV at both deltoid regions on days 0, 3, 7, and 28. Twenty-five patients (64.1%) received rabies immunoglobulin due to having rabies exposure, according to WHO category III. All serum samples were tested for rabies neutralizing antibody (Nab) by the rapid fluorescent focus inhibition test (RFFIT) before vaccination, and on days 14 and 90 after vaccination. All patients had an adequate immune response (Nab titers ≥ 0.5 IU/mL) on days 14 and 90. No patients died of rabies infection. No serious adverse reactions were observed. Expert commentary: CPRV is economic, safe, and immunogenic if given as the modified TRC-ID regimen in children.

Safety, tolerability and efficacy of intradermal rabies immunization with DebioJect™

In a single-center study, 66 healthy volunteers aged between 18 and 50years were randomized to be immunized against rabies with three different injection routes: intradermal with DebioJect™ (IDJ), standard intradermal with classical needle (IDS), also called Mantoux method, and intramuscular with classical needle (IM). "Vaccin rabique Pasteur®" and saline solution (NaCl 0.9%) were administered at D0, D7 and D28. Antigen doses for both intradermal routes were 1/5 of the dose for IM. Tolerability, safety and induced immunogenicity of IDJ were compared to IDS and IM routes. Pain was evaluated at needle insertion and at product injection for all vaccination visits. Solicited Adverse Event (SolAE) and local reactogenicity symptoms including pain, redness and pruritus were recorded daily following each vaccination visit. Adverse events (AE) were recorded over the whole duration of the study. Humoral immune response was measured by assessing the rabies virus neutralizing antibody (VNA) titers using Rapid Fluorescent Focus Inhibition Test (RFFIT). Results demonstrated that the DebioJect™ is a safe, reliable and efficient device. Significant decreases of pain at needle insertion and at vaccine injection were reported with IDJ compared to IDS and IM. All local reactogenicity symptoms (pain, redness and pruritus) after injection with either vaccine or saline solution, were similar for IDJ and IDS, except that IDJ injection induced more redness 30min after saline solution. No systemic SolAE was deemed related to DebioJect™ and classical needles. No AE was deemed related to DebioJect™. No Serious Adverse Event (SAE) was reported during the study. At the end of the study all participants were considered immunized against rabies and no significant difference in humoral response was observed between the 3 studied routes.

Four Thousand Years of Concepts Relating to Rabies in Animals and Humans, Its Prevention and Its Cure

The epitome of the One Health paradigm-and of its shortcomings-rabies has been known to humankind for at least 4000 years. We review the evolution through history of concepts leading to our current understanding of rabies in dogs and humans and its prevention, as transmitted by accessible and surviving written texts. The tools and concepts currently available to control rabies were developed at the end of the 19th Century, including the first live, attenuated vaccine ever developed for humans and the first post-exposure prophylaxis (PEP) regimen. No progress, however, has been made in etiological treatment, leaving clinicians who provide care to animals or patients with symptomatic rabies as powerless today as their colleagues in Mesopotamia, 40 centuries ago. Rabies remains to date the most lethal infectious disease known to humans. Widespread access to timely, effective, and affordable PEP in rural areas of developing countries is urgently needed.

Brief communication (Original). Rabies postexposure vaccination in Thailand: is it performed according to international guidelines?

Background: Animal bites are one of the leading causes of visits to an emergency room (ER) in Thailand. Rabies is an almost invariably fatal disease.

Objectives: We evaluated the appropriateness of rabies vaccination in clinical practice following the World Health Organization (WHO) guidelines.

Methods: All patients who visited the ER at Ramathibodi Hospital of Mahidol University because of mammal bites and received rabies vaccination by the WHO rabies postexposure regimen were enrolled. Data were retrieved from medical records. Wound categories were classified by WHO guidelines both in real practice and by the investigators on subsequent investigation.

Results: The agreement between clinical practice and the WHO guidelines was calculated and reported as kappa statistics. There were 372 eligible patients. The mean age was 36 years and 172 patients were male. The agreement between clinical practice and the WHO guidelines was a disturbing 26.9% with a kappa statistic of -0.02, P = 0.56.

Conclusion: Even in a referral and teaching hospital, rabies postexposure vaccination in Thailand was not appropriate according to WHO guidelines.

Rabies vaccines: where do we stand, where are we heading?

Rabies being the most lethal zoonotic, vaccine-preventable viral disease with worldwide distribution of reservoir wild animals presents unique challenges for its diagnosis, management and control. Although vaccines available are highly effective, which had played the key role in controlling rabies in North America, western Europe and in a number of Asian and Latin American countries, the requirement of multiple doses along with boosters, associated cost to reduce the incidence in wild animals and prophylactic human vaccination has remained a major impediment towards achieving the same goals in poorer parts of the world such as sub-Saharan Africa and southeast Asia. Current efforts to contain rabies worldwide are directed towards the development of more safe, cheaper and efficacious vaccines along with anti-rabies antibodies for post-exposure prophylaxis. The work presented here provides an overview of the advances made towards controlling the human rabies, particularly in last 10 years, and future perspective.

Evaluation of a new five-injection, two-site,intradermal schedule for purified chick embryo cell rabies vaccine: A randomized, open-label, active-controlled trial in healthy adult volunteers in India

BACKGROUND

Human rabies is an ongoing significant public health problem inmany developing countries, with India reporting the highest incidence of rabies-related deaths (∼20,000 per year). Many people living in India cannot afford the standard IM postexposure prophylaxis (PEP) with cell-culture vaccines, which are administered using a 5-dose regimen developed in Essen, Germany. A potentially less expensive intradermal (ID) regimen, based on the Essen regimen, has been developed at the Kempegowda Institute of Medical Sciences (KIMS), Bangalore, India.

OBJECTIVE

The objective of this study was to compare the immunogenicity and local and systemic tolerability of the KIMS-1D regimen with those of the standard Essen IM regimen in healthy adult volunteers in India.

METHODS

This randomized, open-label, active-controlled trial was conductedat the Antirabies Clinic, Medical College, KIMS. Healthy adult volunteers were randomly assigned to receive purified chick embryo cell vaccine (PCECV) using the KIMS-1D regimen (0.1 mL injected ID at 2 body sites on days 0, 3, 7, 14, and 28 ["2-2-2-2-2"]) or the Essen IM regimen (1 mL injected IM at 1 body site on the same days Subjects were followed up for 365 days by the treating physician and encouraged to voluntarily report any adverse events (AEs). Serum rabies virus-neutralizing antibody (RVNA) concentrations were measured before the first injection on day 0 (baseline) and on days 14, 28, 90, 180, and 365, using the rapid fluorescent focus inhibition test.

RESULTS

Ninety-one subjects were enrolled and included in the tolerabilityand immunogenicity analyses. The ID group comprised 45 subjects (26 men, 19 women; mean [SD] age, 20.84 [1.48] years); the IM group, 46 subjects (28 men, 18 women; mean [SD] age, 21.02 [1.16] years). The most common local AEs were pain at the injection site (2/225 [0.9%] in the ID group and 10/230 [4.3%] in the IM group; P < 0.006) and itching at the injection site (5/225 [2.2%] in the ID group and none in the IM group; P = 0.026). All of the AEs were transient and resolved without the need for medication. All subjects had serum RVNA concentrations ≥0.5 IU/mL-considered protective by the World Health Organization-at all follow-up visits. However, the mean RVNA concentrations in the IM group were significantly higher compared with those in the ID group from days 14 to 365 (all, P < 0.001).

CONCLUSION

In this study in healthy volunteers, PEP with PCECV administered using the KIMS-ID regimen was well tolerated and immunologically efficacious for 365 days. Adequate RVNA levels were maintained with the KIMS-ID regimen from days 14 to 365, although these levels were significantly lower than those achieved in the group receiving the Essen IM regimen (all, P < 0.001).

Adverse events following rabies post-exposure prophylaxis: a comparative study of two different schedules and two vaccines

OBJECTIVE

Due to lack of effective treatment for rabies, post-exposure prophylaxis becomes very important. In this study, we investigated side effects developed in patients following administration of rabies post-exposure prophylaxis.

METHODS

A total of 1685 patients were vaccinated. 265 patients (15.7%) administered the Essen regimen with equine rabies immunoglobulin and 1420 patients (84.2%) administered Zagreb regimen. 761 (45.2%) patients were vaccinated with a verocell vaccine; Verorab and 924 patients (54.8%) were vaccinated with Abhayrab.

RESULTS

All side effects were higher in female patients than those of males. The patients with chronic illness also had significantly, increased side effects; headache (12.4%), pain at site of administration (11.3%), and arthralgia (10.5%) compared to the patients without chronic illness. We grouped the patients in three as; 0-15 years, 15-60 years, and 60 years and above. In the first group; fever (21.2%), vomiting (2.4%) and coughing (2.1%); in the second group (15-60 years), headache (8.8%), arthralgia (6.7%) were significantly increased compared to the other groups. Side effects are significantly higher with schema of 2-1-1 and Abhayrab trade mark vaccine, particularly following the first doses.

DISCUSSION

Second generation rabies vaccines are safe, effective and cheaper than HDCV. When fatality of rabies disease is considered, occurring side effects can be tolerated.

Safety and efficacy of novel dermal and epidermal microneedle delivery systems for rabies vaccination in healthy adults

In the present pilot study, intradermal ID delivery systems with a BD microneedle from 1 to 3mm in length, and epidermal delivery (BD skin abrader) through abraded skin surface relative to standard intramuscular injection were evaluated. Circulating neutralizing antibodies were measured against the rabies virus after the Vero cells rabies vaccine was administered at D0, D7, D21 and D49. This clinical evaluation in 66 healthy volunteers shows that ID delivery using BD microneedle technology of 1/4 the IM antigen dose is safe, efficient and reliable, resulting in a protective seroconversion rate. In contrast, the epidermal delivery route did not produce an immune response against the rabies vaccine.

Pre-exposure purified vero cell rabies vaccine and concomitant routine childhood vaccinations: 5-year post-vaccination follow-up study of an infant cohort in Vietnam

Children have a high risk of exposure to rabies in countries where the disease is endemic. This prospective, 5-year study followed two groups of children who had received diphtheria, tetanus, whole-cell pertussis and inactivated poliomyelitis vaccine (DTP-IPV) at 2, 3, 4 months and 1 year (Group B) or concomitant with three doses of purified Vero cell rabies vaccine (PVRV), given at 2, 4 months and 1 year (Group A). Antibody determinations were made annually for 5 years. Data were available from a total of 72 subjects; 30 in Group A and 32 in Group B. In Group A, the percentage of patients immunized against rabies (anti-rabies > or = 0.5 IU/ml) decreased from 100% after the third vaccination to 63%, 5 years later. After 5 years, 93.8% in Group A and 96.7% in Group B had seroprotective diphtheria antibody titers > or = 0.01 IU/ml, and all subjects had anti-polio (type 1, 2 and 3) seroprotective titers > or = 5 1:dil. We conclude that co-administration of PVRV with DTP-IPV elicited protective antibody concentrations to all antigens that persist for at least 5 years, with continued protection against rabies in over 60% of subjects. These results are consistent with integration of pre-exposure rabies vaccination into the Expanded Program on Immunization (EPI) in countries where rabies is endemic.

Intradermal, epidermal and transcutaneous vaccination: from immunology to clinical practice

The dermis and epidermis are alternative sites for prophylactic vaccination that have received renewed interest in recent years, not only because of the ease of access to the skin, but also its unique immunological properties. This review discusses the characteristics of the skin, current knowledge on skin immunity and clinical experience with cutaneous immunization against infectious diseases, with a special focus on intradermal immunization. The most widely accepted paradigm explaining the efficacy of cutaneous immunization is reviewed and recent research suggesting where this paradigm may need some refinement is highlighted. Clinical investigations that have concentrated on the intradermal route to vaccinate against influenza, rabies or hepatitis B support the current knowledge on skin immunity and, when combined with recent progress made in the development of user-friendly injection systems, have stimulated the ongoing clinical development of novel vaccines.

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.

Adverse Effects of Rabies Pre- and Postexposure Prophylaxis in 290 Health-Care-Workers Exposed to a Rabies Infected Organ Donor or Transplant Recipients

The recent unfortunate rabies transmissions through solid organ transplants of an infected donor in Germany required the initiation of a vaccination program to protect health care workers (HCWs) with close contact to rabies-infected patients. A systematic follow-up of adverse effects was initiated. Rabies postexposure prophylaxis (PEP) was started in 269 HCWs at four German hospitals. Pre-exposure prophylaxis (PreEP) was administered to 74 HCWs caring for an already diagnosed rabies patient. At each vaccination date, HCWs were interviewed for symptoms possibly representing adverse effects. Adverse effects of PEP and PrePEP were compared. Out of 269 HCWs, 216 were included for the investigation of adverse effects. Of these 216 HCWs, 114 (53%) individuals developed at least one systemic adverse effect. Incidences of tiredness (30.6%), malaise (26.4%), headache (26.9%), dizziness (14.8%), and chills (13.0%) declined in the course of PEP (p < 0.05), whereas incidences of fever (7.4%), paraesthesias (7.9%), arthralgias (1.9%), myalgias (4.2%), nausea (9.3%), diarrheas (2.8%) and vomiting (1.4%) did not. In 11 (5.1%) HCWs PEP was discontinued mostly due to adverse reactions (four suffered strong headaches, two HCWs meningeal irritations, two chills, one paraesthesia, one malaise, and one a rush). Systemic effects of PEP or PreEP did not differ significantly. Despite relatively high incidences of moderate severe adverse reactions rabies PEP is safe. Strong headache, tiredness, dizziness, and paraesthesias are the most important postvaccinal symptoms. Vaccinees suffering from adverse effects of PEP must be strongly encouraged to complete PEP, as it is to date the only protection against fatal rabies.

Survival of neutralizing antibody in previously rabies vaccinated subjects: A prospective study showing long lasting immunity

Physicians dealing with potential rabies exposures and travel medicine are frequently asked how long previous pre- or post-exposure rabies vaccination induced immunity persists. We therefore carried out a prospective study on 118 rabies vaccine recipients who had received pre- or post-exposure regimens with tissue culture rabies vaccines by intramuscular or intradermal schedules 5-21 years previously. Rabies neutralizing antibody was detectable in the sera of all subjects on day 0. They then received one intradermal 0.1 mL booster injection on days 0 and 3. Neutralizing antibody determination was carried out on days 5, 7 and 14. All except one subject showed an accelerated antibody response following the two booster injections. Vaccination with a WHO recognized tissue culture rabies vaccine evokes long lasting immunity. This study supports current recommendations that immunity is long lasting and that boosters without immunoglobulin are sufficient even when prior vaccination was longer than 5 years previously.

The real cost of rabies post-exposure treatments

The total costs to all payers, i.e., a societal perspective, of four rabies post-exposure regimens were evaluated in two dog bite centres and four local health centres in India. Results showed that the Thai Red Cross intra-dermal regimen (TRC-ID), which uses only one-fifth of the IM dose of purified vero cell vaccine (PVRV) was at most 20% more expensive than use of Purified Chick Embryo Cell (PCEC) vaccine at one-tenth of the IM dose: this cost difference needs to be balanced with the small margin of safety of low potency doses. In local health centres where the staffs are not specially trained in rabies vaccination, the Zagreb intra-muscular regimen is an economical option.

An immunogenicity study of a newly introduced purified vero cell rabies vaccine (Abhayrab) manufactured in India

Purified Vero cell culture rabies vaccine "Abhayrab" manufactured by Human Biologicals Institute, Ooty, India was subjected for immunogenicity studies. Pre-exposure study was undertaken on 60 healthy volunteers (Group I) with vaccination on days 0, 7 and 21. A group of 75 patients of category II (Group II), 67 of category III (Group III) were given post-exposure prophylaxis and 88 patients of category III were administered with rabies immunoglobulins (Group IV) along with post-exposure prophylaxis as per World Health Organization (WHO) recommendations with a booster on day 90. The volunteers and patients vaccinated showed very few adverse side effects. The blood samples collected from volunteers (Group I) on days 14, 35 and 365 and patients (Group II-IV) on days 14, 30, 90 and 365 showed geometric mean titres (GMT) of >0.5 IU/ml. The study indicated new rabies vaccine manufactured in India was found to be safe and immunogenic.

Serum antibody responses after intradermal vaccination against influenza

BACKGROUND

If found to be safe and immunogenic, reduced doses of influenza vaccine given by the intradermal route could increase the number of available doses of vaccine.

METHODS

In an open-label study, we randomly assigned 119 subjects to receive an intradermal injection of trivalent inactivated influenza vaccine, containing 6 mug of hemagglutinin for each antigen (40 percent of the usual dose), and 119 to receive an intramuscular injection of the standard dose of 15 mug of hemagglutinin for each antigen. The two groups were subdivided according to age (18 to 60 years and older than 60 years).

RESULTS

Among subjects who were 18 to 60 years of age, serum antibody responses were vigorous and did not differ significantly between the intradermal and intramuscular groups, and all subjects had hemagglutination-inhibition (HAI) titers of at least 1:40. Although the subjects who were older than 60 years of age also had a vigorous antibody response, there was a trend toward a better response in the intramuscular route, but this finding was significant only for antigen to the H3N2 strain. Nevertheless, 100 percent of older subjects in the intramuscular group and 93 percent of such subjects in the intradermal group had an HAI antibody titer to the H3N2 strain of more than 1:40, and 100 percent in each group had a titer of this level for both the H1N1 and B strains. Local pain was significantly more common in the intramuscular group than in the intradermal group among subjects who were 18 to 60 years of age but not among subjects who were over 60 years old. Signs of local inflammation were significantly more common among subjects in the intradermal group than among those in the intramuscular group, in both age groups.

CONCLUSIONS

As compared with an intramuscular injection of full-dose influenza vaccine, an intradermal injection of a reduced dose resulted in similarly vigorous antibody responses among persons 18 to 60 years of age but not among those over the age of 60 years.

Economical multi-site intradermal regimen with purified chick embryo cell vaccine (Rabipur) prevents rabies in people bitten by confirmed rabid animals

OBJECTIVE

To determine the efficacy of a cost-effective multi-site intradermal regimen with purified chick embryo cell vaccine (PCECV, Rabipur) in preventing rabies in people bitten by confirmed rabid dogs.

METHODS

Thirty-two people of different age groups who were severely bitten by confirmed rabid dogs were immunized with PCECV using the WHO recommended multi-site intradermal regimen of 0.1 mL of vaccine at eight sites on day 0, at four sites on day 7, and at one site each on days 28 and 90. In addition, passive immunization with human or equine rabies immunoglobulin was administered to 22 of these people before administering vaccine. They were followed for up to 3 years with periodic estimation of neutralizing antibody levels in their serum by mouse neutralization test (MNT).

RESULTS

There was an excellent immune response with more than protective titers (>0.5 IU/mL) on all days tested up to the end of the 3-year observation period. More significantly, protective titers were seen in all subjects by day 7. Only minimal side effects were observed. All the patients were doing well at the end of the 3-year observation period, which is generally considered to be the maximum incubation period for rabies in humans.

CONCLUSIONS

It can be concluded that this multi-site regimen with or without passive immunization has prevented the development of rabies encephalitis in these people bitten by confirmed rabid dogs. This should encourage more such studies, so that this cost-effective economical regimen with safe and potent cell culture vaccines can replace highly reactogenic neural tissue-derived Semple vaccine in developing countries such as India.

Immunogenicity, safety and lot consistency in adults of a chromatographically purified Vero-cell rabies vaccine: a randomized, double-blind trial with human diploid cell rabies vaccine

The immunogenicity and safety of a chromatographically purified rabies vaccine (CPRV) was evaluated using US veterinary medical students. In the first study, 242 healthy adults were enrolled in a randomized, modified double-blind, multicenter trial and received five doses of either CPRV or human diploid cell vaccine (HDCV) by intramuscular injection on days 0, 3, 7, 14, and 28 concurrently with human rabies immunoglobulin in a simulated post-exposure prophylaxis regimen. Post-immunization titers in the CPRV and HDCV groups reached 0.5 IU/ml (the WHO-recommended minimally acceptable titer) or greater in all subjects in both vaccine groups by day 14 and remained above that level through day 90. In the second study, 438 healthy adults were enrolled in a randomized, double-blind, multicenter trial and assigned to receive five doses from one of three lots of CPRV by intramuscular injection on days 0, 3, 7, 14, and 28 in a simulated post-exposure prophylaxis regimen to evaluate lot consistency. Post-immunization titers rapidly increased to over 0.5 IU/ml by day 14 for all subjects and remained above that level through day 42 when the study was terminated. The three lots were considered equivalent. The percentage of subjects with at least one local reaction during the five-dose regimen was slightly lower in the CPRV group than in the HDCV group (P=0.06). The most frequently reported local reaction for all doses of vaccine was pain at the injection site. Headache, myalgia, and malaise were the most frequently reported systemic events. The percentage of subjects with at least one systemic event was significantly lower for CPRV (P=0.0084). No vaccine-related serious adverse reaction was reported in these studies. The results of these studies indicate that CPRV administered intramuscularly to healthy adults is immunogenic and is associated with fewer local and systemic reactions than HDCV.

Predictive factors for the neutralizing antibody response following pre-exposure rabies immunization: validation of a new booster dose strategy

A prospective cohort of 312 subjects who received pre-exposure rabies immunization and who were monitored serologically with a 10-year follow-up was assessed using multivariate analysis. The aim was to propose a new booster dose strategy by identifying predictive factors for the durability of the neutralizing antibody response. Evaluation bore on several factors relating to: (1) demographic characteristics: age, gender; (2) vaccines: type of vaccine (HDCV or PVRV), injection regimen (D0-D28-D365 or D0-D7-D28-D365) and vaccine lots' antigenic potency; and (3) resulting antibody titers. Logistic regression analysis enabled the authors to establish a predictive model for immunized subjects' serological status at ten years' follow-up expressed as a P probability for seroreversion (antibody titer <0.5 IU/ml). Highly significant factors were the immunization regimen, the type of vaccine used and the antibody titer at D379. A P value <0.4 identified subjects as "good" responders who were sure to be have satisfactory antibody titers at 10 years and who required a single booster dose every 10 years. A P value >/=0.4 identified subjects as "poor" responders in whom a specific follow-up and booster dose strategy is proposed. This new immunization strategy could at least be applied to subjects with a frequent risk of exposure, as defined by institutional recommendations. This new immunization strategy should nevertheless undergo an external validation and a cost-effectiveness evaluation.