Rabies preexposure prophylaxis with human diploid cell rabies vaccine: a dose-response study

Immune Response of Inactivated Rabies Vaccine Inoculated via Intraperitoneal, Intramuscular, Subcutaneous and Needle-Free Injection Technology-Based Intradermal Routes in Mice

Inoculation routes may significantly affect vaccine performance due to the local microenvironment, antigen localization and presentation, and, therefore, final immune responses. In this study, we conducted a head-to-head comparison of immune response and safety of inactivated rabies vaccine inoculated via intraperitoneal (IP), intramuscular (IM), subcutaneous (SC) and needle-free injection technology-based intradermal (ID) routes in ICR mice. Immune response was assessed in terms of antigen-specific antibodies, antibody subtypes and neutralizing antibodies for up to 28 weeks. A live rabies virus challenge was also carried out to evaluate vaccine potency. The dynamics of inflammatory cell infiltration at the skin and muscle levels were determined via histopathological examination. The kinetics and distribution of a model antigen were also determined by using in vivo fluorescence imaging. Evidence is presented that the vaccine inoculated via the ID route resulted in the highest antigen-specific antibody and neutralizing antibody titers among all administration routes, while IP and IM routes were comparable, followed by the SC route. Antibody subtype analysis shows that the IP route elicited a Th1-biased immune response, while SC and IM administration elicited a prominent Th2-type immune response. Unexpectedly, the ID route leads to a balanced Th1 and Th2 immune response. In addition, the ID route conferred effective protection against lethal challenge with 40 LD50 of the rabies CVS strain, which was followed by IP and IM routes. Moreover, a one-third dose of the vaccine inoculated via the ID route provided comparable or higher efficacy to a full dose of the vaccine via the other three routes. The superior performance of ID inoculation over other routes is related to longer local retention at injection sites and higher lymphatic drainage. Histopathology examination reveals a transient inflammatory cell infiltration at ID and IM injection sites which peaked at 48 h and 24 h, respectively, after immunization, with all side effects disappearing within one week. These results suggest that needle-free injection technology-based ID inoculation is a promising strategy for rabies vaccination in regard to safety and efficacy.

Microarray patches: scratching the surface of vaccine delivery

INTRODUCTION

Microneedles are emerging as a promising technology for vaccine delivery, with numerous advantages over traditional needle and syringe methods. Preclinical studies have demonstrated the effectiveness of MAPs in inducing robust immune responses over traditional needle and syringe methods, with extensive studies using vaccines targeted against different pathogens in various animal models. Critically, the clinical trials have demonstrated safety, immunogenicity, and patient acceptance for MAP-based vaccines against influenza, measles, rubella, and SARS-CoV-2.

AREAS COVERED

This review provides a comprehensive overview of the different types of microarray patches (MAPs) and analyses of their applications in preclinical and clinical vaccine delivery settings. This review also covers additional considerations for microneedle-based vaccination, including adjuvants that are compatible with MAPs, patient safety and factors for global vaccination campaigns.

EXPERT OPINION

MAP vaccine delivery can potentially be a game-changer for vaccine distribution and coverage in both high-income and low- and middle-income countries. For MAPs to reach this full potential, many critical hurdles must be overcome, such as large-scale production, regulatory compliance, and adoption by global health authorities. However, given the considerable strides made in recent years by MAP developers, it may be possible to see the first MAP-based vaccines in use within the next 5 years.

Comparison of equivalent fractional vaccine doses delivered by intradermal and intramuscular or subcutaneous routes: A systematic review

BACKGROUND

For certain vaccines, dosing can be reduced by intradermal (ID) immunization without loss of immunogenicity, as an alternative to standard routes of administration. However, a certain level of dose-sparing might also be achieved by reducing doses of intramuscular (IM) or subcutaneous (SC) vaccines.

METHOD

We conducted a systematic review comparing identical reduced amounts of antigen delivered by either ID, or IM/SC routes (PROSPERO registration no. CRD42020151725).

RESULTS

Of 6015 articles identified, we included 26 articles, covering eight different vaccines. Equivalent immune responses were demonstrated in 19/26 studies, and 7/26 studies suggested inferior immune responses after IM/SC immunization.

CONCLUSIONS

We conclude that fractional dosed IM/SC vaccination is at best as immunogenic, but potentially inferior to ID vaccination. The safety profiles were at large comparable, although minor local adverse events were more common after ID delivery. Future vaccine trials, depending on the platform used, should add a fractional dose IM/SC arm, besides a fractional dose ID arm.

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.

Rabies post-exposure vaccination in 2 visits within a week: A 4-site intradermal regimen

Rabies is fatal in all unvaccinated patients bitten by dogs, and so post-exposure vaccine regimens must be robust enough to ensure their survival under all conditions. Treatment tends to be excessive for most people, but there is justified anxiety about reducing vaccine dosage and shortening regimens. Recently, World Health Organisation (WHO) recommended one week primary post-exposure intradermal regimens requiring 3 clinic visits, but these are unlikely to prove economical where rabies vaccination is most needed, in deprived rural areas of Africa and Asia. A highly immunogenic regimen involving two doses of intradermal vaccine given one week apart has advantages over other regimens. Anyone exposed to a possibly rabid animal would be given intradermal (ID) injections at 4 sites using a whole vial of vaccine. Those who had not been previously vaccinated would be given 2-site ID injections using half a vial one week later. Those who might be immunosuppressed could be given an optional single ID dose on day 28. The rationale for this regimen is discussed in the context of the recently revised WHO recommendations for rabies prophylaxis.

Immunogenicity, safety and tolerability of intradermal influenza vaccines

Intradermal influenza vaccination has been studied for more than 80 y. The revived interest in this strategy of vaccination is a result of the innovative technologies in needle design allowing more precise injection and making the device easier to use. Furthermore, clinical trials on these novel devices have demonstrated significant dose sparing effects, improved immunogenicity and very few adverse effects. This review compares intradermal vaccination with various devices with subcutaneous and intramuscular vaccination. We also discussed the role of topical adjuvant before intradermal vaccination.

Intradermal vaccination using the novel microneedle device MicronJet600: Past, present, and future

Intradermal immunization has become a forefront of vaccine improvement, both scientifically and commercially. Newer technologies are being developed to address the need to reduce the dose required for vaccination and to improve the reliability and ease of injection, which have been major hurdles in expanding the number of approved vaccines using this route of administration. In this review, 7 y of clinical experience with a novel intradermal delivery device, the MicronJet600, which is a registered hollow microneedle that simplifies the delivery of liquid vaccines, are summarized. This device has demonstrated both significant dose-sparing and superior immunogenicity in various vaccine categories, as well as in diverse subject populations and age groups. These studies have shown that intradermal delivery using this device is safe, effective, and preferred by the subjects. Comparison with other intradermal devices and potential new applications for intradermal delivery that could be pursued in the future are also discussed.

A micro-sterile inflammation array as an adjuvant for influenza vaccines

There is an urgent need of adjuvants for cutaneous vaccination. Here we report that micro-sterile inflammation induced at inoculation sites can augment immune responses to influenza vaccines in animal models. The inoculation site is briefly illuminated with a handheld, non-ablative fractional laser before the vaccine is intradermally administered, which creates an array of self-healing microthermal zones (MTZs) in the skin. The dying cells in the MTZs send “danger” signals that attract a large number of antigen-presenting cells, in particular, plasmacytoid dendritic cells (pDCs) around each MTZ forming a micro-sterile inflammation array. A pivotal role for pDCs in the adjuvanticity is ascertained by significant abrogation of the immunity after systemic depletion of pDCs, local application of a TNF-α inhibitor, or null mutation of IFN regulatory factor7 (IRF7). In contrast to conventional adjuvants that cause persistent inflammation and skin lesions, micro-sterile inflammation enhances efficacy of influenza vaccines, yet with diminished adverse effects.

Delivery systems for intradermal vaccination

Intradermal (ID) vaccination can offer improved immunity and simpler logistics of delivery, but its use in medicine is limited by the need for simple, reliable methods of ID delivery. ID injection by the Mantoux technique requires special training and may not reliably target skin, but is nonetheless used currently for BCG and rabies vaccination. Scarification using a bifurcated needle was extensively used for smallpox eradication, but provides variable and inefficient delivery into the skin. Recently, ID vaccination has been simplified by introduction of a simple-to-use hollow microneedle that has been approved for ID injection of influenza vaccine in Europe. Various designs of hollow microneedles have been studied preclinically and in humans. Vaccines can also be injected into skin using needle-free devices, such as jet injection, which is receiving renewed clinical attention for ID vaccination. Projectile delivery using powder and gold particles (i.e., gene gun) have also been used clinically for ID vaccination. Building off the scarification approach, a number of preclinical studies have examined solid microneedle patches for use with vaccine coated onto metal microneedles, encapsulated within dissolving microneedles or added topically to skin after microneedle pretreatment, as well as adapting tattoo guns for ID vaccination. Finally, technologies designed to increase skin permeability in combination with a vaccine patch have been studied through the use of skin abrasion, ultrasound, electroporation, chemical enhancers, and thermal ablation. The prospects for bringing ID vaccination into more widespread clinical practice are encouraging, given the large number of technologies for ID delivery under development.

Intradermal rabies vaccination: the evolution and future of pre- and post-exposure prophylaxis

Inactivated rabies vaccines have been used to pioneer the immunological and economical advantages of intradermal (ID) administration over 35 years. Vaccine shortages or its prohibitive cost stimulated studies of various doses, frequency and sites of injection. An economical regimen for pre-exposure prophylaxis requires one-tenth of an intramuscular dose, but the early popularity of the method has been stifled by pharmaceutical regulations. There has also been reluctance to use multiple-site post-exposure ID regimens, except in a very few Asian counties. A new four-site ID regimen could overcome many of the problems encountered to date. The time is ripe to make dramatic progress towards efficient use of the current excellent vaccines globally, wherever there is a shortage of vaccine or funds.

Assessing the relationship between antigenicity and immunogenicity of human rabies vaccines when administered by intradermal route: results of a metaanalysis

The metadata of 10 published studies and 3 vaccine trial reports comprising of 19 vaccine cohorts from four countries conducted over a period of 23 years (1986 - 2009) was used for metaanalysis. The vaccines studied were purified chick embryo cell vaccine (Rabipur, India & Germany), purified vero cell rabies vaccine (Verorab, France; Indirab, India) & human diploid cell vaccine (MIRV, France).The potency of these vaccines varied from 0.55 IU to 2.32 IU per intradermal dose of 0.1 ml per site. The vaccines were administered to 1,011 subjects comprising of 19 cohorts and using five different ID regimens. The immunogenicity was measured by assays of rabies virus neutralizing antibody (RVNA) titres using rapid fluorescent focus inhibition test (RFFIT) [15 cohorts] and mouse neutralization test (MNT) [4 cohorts]. The statistical analysis of the data was done by Karl Pearson's correlation coefficient to measure the relationship between antigenicity and immunogenicity. It was revealed that, there was no significant linear relationship between antigenicity and immunogenicity of rabies vaccines when administered by intradermal route. (p> 0.230 and p>0.568).

Potency requirements of rabies vaccines administered intradermally using the Thai Red Cross regimen: investigation of the immunogenicity of serially diluted purified chick embryo cell rabies vaccine

To determine the minimum vaccine potency per intradermal dose required to elicit an adequate immune response using the Thai Red Cross (TRC) regimen (2-2-2-0-1-1), healthy volunteers received 0.1 mL volumes of PCECV containing decreasing amounts of antigen. Subjects also received HRIG to evaluate potential interference with antibody production. Results indicated that when each 0.1 mL intradermal dose of PCECV contained antigen corresponding to 0.32 IU per intramuscular dose, every subject had titers above 0.5 IU/mL by day 14. These results confirm that the current World Health Organization (WHO) recommendations for vaccine potency (2.5 IU per intramuscular dose) are sufficient for use in the Thai Red Cross intradermal regimen.

Improved serological response to human diploid cell rabies vaccine when given simultaneously with antirabies hyperimmune globulin

BACKGROUND

The prevention of rabies in Mexico continues to be an important goal for the health sector. Although the prevalence of this disease continues to fall, between 1990 and 1995 a total of 238 cases were registered (an average of 40 cases annually), with a mean annual incidence of 0.04 cases per 100,000 inhabitants and a mortality of almost 100%, so that it is important to rely on highly effective vaccines with few side effects. The objective of this work was to evaluate seroconversion and tolerance to the human diploid cell antirabies vaccine administered to individuals with a history of exposure to rabies, to compare these results with those reported in the literature for the Fuenzalida vaccine, a rabies vaccine produced in the brain tissue of suckling mice, and to find the role antirabies hyperimmune gamma globulin plays in the concentration of post-vaccination antibody concentrations.

METHODS

An analytical transverse study was carried out in 40 children and adults with a history of rabies exposure who were given a complete, five-dose intramuscular schedule of the human diploid cell rabies vaccine. Subjects were followed daily, and local and systemic signs and symptoms were recorded. Two blood samples (at baseline and at the end of the vaccination schedule) were taken and antibody titers against rabies glycoprotein, using the ELISA technique, were measured.

RESULTS

Adverse side effects produced by the human diploid cell antirabies vaccine, such as frequency of pain, erythema, itching, and regional adenopathy were fewer than those reported in the literature for the Fuenzalida vaccine (p < 0.05), and of induration and local pain (p < 0.05) in relation to the latter vaccine. All patients seroconverted, producing geometric mean antibody titers of 6.22 IU/mL, an arithmetic mean titer of 9.66 IU/mL with a SD of 9.1 IU/mL. The level of tolerance to the diploid cell vaccine was good and its adverse effects were minimal and fewer than those reported for the Fuenzalida rabies vaccine. Patients receiving the diploid cell vaccine plus antirabies hyperimmune gamma globulin developed higher antibody titers (measured by ELISA test) at the end of the vaccination schedule than those only receiving the vaccine.

CONCLUSIONS

These results are important in order to achieve an adequate and opportune level of protection provided by prophylactic vaccines to patients with exposure to rabies.

Immunogenicity and safety of low-dose intradermal rabies vaccination given during an Expanded Programme on immunization session in Viet Nam: results of a comparative randomized trial

The World Health Organization recently recommended a rabies vaccine pre-exposure schedule using 3 intradermal (i.d.) injections of one-fifth the standard intramuscular (i.m.) dose of current cell culture vaccines as a cost-reducing alternative for developing countries. As a strategy to improve further the acceptability of childhood rabies immunization, we assessed, in a controlled, randomized trial performed in 240 Vietnamese infants, the possibility of associating i.d. administration of a one-fifth dose of purified Vero-cell rabies vaccine (PVRV) with routine Expanded Programme on Immunization vaccines given at 2, 3 and 4 months of age (diphtheria, tetanus, whole-cell pertussis and inactivated poliomyelitis combined vaccine, DTP-IPV). Safety and immunogenicity results were compared with a group of infants given 2 i.m. doses of PVRV (2, 4 months) in association with DTP-IPV (2, 3, 4 months). After i.d. injection, more infants experienced local reactions, particularly redness, but these reactions were generally mild and transient. The rate of systemic reactions was the same in both groups. Although the rabies antibody titres (rapid fluorescent focus inhibition test) were higher 1 month after the third vaccine dose in the i.m. group (30.6 IU/mL vs 12.0 IU/mL in the i.d. group), all infants in both groups had achieved WHO-acceptable protective antibody titres (> or = 0.5 IU/mL) at this time. There was no evidence for any interference between DTP-IPV and rabies vaccine, supporting the interest of a low-dose i.d. PVRV pre-exposure regimen in infants living in rabies-endemic developing countries.

Safety and immunogenicity of Lyssavac Berna human diploid cell rabies vaccine in healthy adults

A clinical trial testing the safety and immunogenicity of a newly developed human diploid cell rabies vaccine (Lyssavac-HDC) was conducted on subjects at three colleges of veterinary medicine in the United States. Lyssavac-HDC is a sterile lyophilized vaccine containing no antibiotics or preservatives and is administered intramuscularly as a 0.5 ml dose of vaccine containing at least 2.5 i.u. of rabies inactivated antigen per dose. Subjects were given either a three dose pre-exposure series (days 0, 7, and 28), followed by one booster dose of vaccine (day 360); or a five dose simulated post-exposure series of injections (days 0, 3, 7, 14, and 28). All subjects in the post-exposure and pre-exposure groups possessed adequate levels of rabies neutralizing antibody (> or = 5) when tested on day 14 and day 28, respectively. Subjects in the pre-exposure group demonstrated a vigorous anamnestic response after the administration of one booster dose of vaccine on day 360. The type and severity of local and systemic reactions observed were comparable to other primary cell culture rabies vaccines. Significantly, there were no type III hypersensitivity reactions reported in subjects previously immunized with Lyssavac-HDC after the administration of a booster dose of vaccine on day 360.

Human rabies: a review

Human rabies is a rarely observed but frequently prophylaxed disease in North America. Presented in this review is a typical emergency department case and a summary of the epidemiology of the rabies virus, its clinical appearances, diagnosis, and management. Emphasis is placed on issues pertinent to the emergency physician practicing in the United States. Current recommendations for the administration of both active and passive immunotherapy for preexposure and postexposure prophylaxis are discussed. A treatment algorithm to aid in the decisions faced by a practicing physician regarding proper animal management and patient therapy and future prospects for the control of rabies in wild animal populations are also included.

Longevity of rabies antibody titre in recipients of human diploid cell rabies vaccine

Sera from individuals across the USA and Peace Corps Volunteers (PCV) were assayed for neutralizing antibody to human diploid cell rabies vaccine (HDCV). A pairwise comparison between intramuscular (i.m.) and intradermal (i.d.) administration, PCV and non-PCV, revealed statistically significant differences between i.m. and i.d. for PCV and non-PCV, and between PCV and non-PCV for i.d. and i.m. administration. Survival analysis and frequency tables employing chi 2 tests determined that the percentage probability of maintaining an adequate titre from 1.5-2.0 years after primary vaccination was 99% in non-PCV i.m., 93% in non-PCV i.d., 88% in PCV i.m., and 64% in PCV i.d.

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.

A new vaccine against tick-borne encephalitis: initial trial in man including a dose-response study

A new vaccine against tick-borne encephalitis was investigated in 56 healthy volunteers randomized for five different doses of antigen in a comparative group trial. Good tolerability and high immunogenicity were found using three different antibody test systems. The dose response study revealed that there was a strong relationship between the amount of antigen administered and the antibody response over the range of 0.03-3.0 micrograms antigen per dose.

Human diploid cell rabies vaccine purified by zonal centrifugation: a controlled study of antibody response and side effects following primary and booster pre-exposure immunizations

Systemic allergic reactions following booster immunizations have complicated rabies pre-exposure prophylaxis with the human diploid cell rabies vaccine licensed in the US (conventional HDCV). We conducted two studies comparing an HDCV purified by zonal centrifugation to conventional HDCV. In a study of primary pre-exposure immunization, volunteers received one of four regimens: three 1.0-ml intramuscular (i.m.) or 0.1-ml intradermal (i.d.) doses of conventional or purified HDCV over 28 days. Although volunteers vaccinated i.m. had significantly greater rabies neutralizing antibody titres (VNA) 49 days, 91 days and 26 months after immunization began than volunteers vaccinated i.d. (p less than 0.005-p less than 0.05), there were no significant differences between vaccines. In a study of booster immunizations, 77 volunteers immunized with conventional HDCV 2 years earlier received a 0.1-ml i.d. booster with either conventional or purified HDCV. VNA was significantly greater with the conventional HDCV on days 7 and 28 after booster, but not on day 365. A moderate or severe reaction was reported by 5 (13%) of the 40 persons who received boosters with conventional HDCV, versus none of 37 who received the purified HDCV (p = 0.03). Purified HDCV appears to be preferable to conventional HDCV for booster vaccination.