Early rabies antibody response to intramuscular booster in previously intradermally immunized travelers using human diploid cell rabies vaccine

Long-term immunity and the effect of one or two booster doses with a lyophilized human rabies vaccine (human diploid cells) at 10 years post primary vaccination in China

Background: To evaluate the persistence of antibody for 10 years, and investigate the effect of one or two booster doses with Kanghua human diploid cells rabies vaccine (HDCV) in China.Methods: Participants were re-recruited at year 10 post the primary phase 3 clinical study. Some of them in Kanghua HDCV group who had been boosted one dose at year 8, received one more dose at this boosted study. Participants who never boosted were randomly assigned to boost 1 or 2 doses of Kanghua HDCV. Blood samples were collected at day 0, 1, 3, 7, and 14. Safety was evaluated from day 0-14.Results: At year 10 after primary vaccination, the seroconversion rates of neutralizing antibody were 98.28-100% in Kanghua and Pasteur groups.After booster, the seroconversion rate in each group reached to 100% from day 7 to day 14. GMCs were similar in the groups with the same booster doses, and two doses of booster induced higher levels of antibody. The reported rates of solicited local and systemic adverse reaction were low, and no serious adverse events were found through the boosted study.Conclusion: 5 doses of Kanghua HDCV maintained long-term immunity at least 10 years. One or two doses of booster, rapidly triggered 100% protection against rabies virus.Trial registration: ClinicalTrials.gov: NCT03774628.

Rabies Antibody Response After Booster Immunization: A Systematic Review and Meta-analysis

Although fatal once symptomatic, rabies is preventable by administration of pre- and post-exposure vaccines. International guidelines suggest lifelong protection by a pre-exposure vaccination scheme followed by timely post-exposure vaccines. Rapidity and magnitude of the antibody recall response after booster inoculation are essential, as many people have been previously immunized a long time ago. The objective of this study was therefore to systematically review the evidence on the boostability of rabies immunization to date. We included 36 studies, of which 19 studies were suitable for meta-analysis. Reduced antibody levels were found after intradermal primary schedules as compared to intramuscular schedules. However, responses after booster immunization were adequate for both routes. Although studies showed that antibody levels decline over time, adequate booster responses were still retained over long time intervals indicating that post-exposure treatment is effective without extra measures after long periods of time.

Pre-exposure prophylaxis against rabies in children: safety of purified chick embryo cell rabies vaccine (Vaxirab N) when administered by intradermal route

Animal bites in humans are a public health problem. Children are the most frequently exposed, representing 50% of human exposures in canine rabies infected areas. Pre-exposure vaccination using cell culture vaccines is a safe and effective method of preventing rabies among children in these highly endemic regions. The development of immunological memory after pre exposure vaccination has established long lasting immunity against rabies in humans. The present study assessed the safety of Purified Chick Embryo cell Rabies Vaccine (Vaxirab N) administered as a three-dose intradermal pre-exposure regimen on days 0, 7, and 21 in healthy volunteered children of 5-10 y age group from an urban poor locality in Bangalore, India. One hundred fifty three apparently healthy children of both sexes between 5 and 10 y of age were enrolled in the study and 123 (80.4%) completed all three doses. A total of 405 doses of intradermal vaccine was administered, among which 25 adverse reactions were reported from 17 children. The adverse reactions were pain at the injection site 15 (3.7%), redness 2 (0.5%), itching at the site of injection 1 (0.2%), fatigue 1 (0.2%), fever 3 (0.7%), myalgia 2 (0.5%) and allergy 1 (0.2%). All reactions subsided without any complication. In conclusion, pre exposure vaccination against rabies is a useful tool for protecting children living in highly endemic regions and Vaxirab N has proved to be safe and well tolerated by intradermal route among children.

Rabies antibody seroprotection rates among travelers in Nepal: "rabies seroprotection in travelers"

BACKGROUND

Rabies preexposure immunization is recommended for international travelers who are at risk for exposure to rabid animals, especially in areas where postexposure treatment may be limited. Rabies antibody seroprotection rates among international travelers has not been previously investigated.

OBJECTIVE

To assess preexisting rabies seroprotection among travelers presenting to a health clinic in Nepal.

METHODS

A prospective convenience sample of international travelers evaluated at a health center in Kathmandu, Nepal during a 2-month period. Subjects were eligible for inclusion if they had received rabies preexposure vaccination within the previous 5 years. Demographic information and vaccination records of rabies preexposure prophylaxis were obtained. Consenting subjects provided serum for rabies antibody measurement measured using the rapid fluorescent focus inhibition test. A dilution greater than or equal to 1:5 (0.5 IU/mL) was considered positive. Data were analyzed using chi-squares and two-sample t-tests with unequal variances.

RESULTS

A total of 43 patients consented to enroll. Complete data were available for 38 patients. Subjects had received human diploid cell vaccine (HDCV) or purified Vero cell rabies vaccine (PVRV) vaccine, either via the intradermal or intramuscular route. All patients had adequate antibody titers except one, who had a titer below 0.5 IU/mL. There was no statistically significant relationship between antibody titer and type of vaccine, route of administration, time since vaccination, number of vaccinations, or patient age.

CONCLUSIONS

Among 38 travelers to Nepal who had received documented preexposure rabies HDCV or PVRV vaccination series, 37 demonstrated adequate titers of > or =0.5 IU/mL and would be considered boostable if exposed to rabies virus. One traveler had a titer of <0.5 IU/mL. Type of vaccine, method of administration, number of vaccinations, and time since vaccination did not influence rabies antibody titer. Rabies vaccination with HDCV and PVRV vaccine was effective in stimulating adequate seroprotection in this sample of travelers.

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.