Persistence of Rabies Antibody 5 Years after Postexposure Prophylaxis with Vero Cell Antirabies Vaccine and Antibody Response to a Single Booster Dose

Abstract

This study was done to investigate the antibody response to a Vero cell antirabies vaccine, the persistence of antibody for 5 years, and the effect of a booster dose after this interval. From August 2005 to February 2011, a total of 195 patients were enrolled into our study due to an animal bite. The Essen intramuscular (i.m.) regimen, which is recommended by the WHO for modern vaccines used in postexposure treatment, was adopted in this study. Blood samples were obtained on day 0, day 7, day 14, day 45, year 1, year 2, year 3, year 4, year 5, and year 5 plus 14 days. Immunogenicity was evaluated by the titration of neutralizing antibodies with a rapid fluorescent focus inhibition test (RFFIT). Seroconversion was expressed as the seroconversion rate (SCR). A secondary quantitative evaluation criterion, other than the seroconversion level, was the geometric mean titer (GMT). Of the 195 enrolled patients, 168 (86.4%) of them completed the whole study. No serious adverse reactions to the vaccine were reported during vaccination, the 5-year follow-up period, or revaccination. On day 14, the rabies antibody GMT value was 8.87 IU/ml in the vaccinees. During the next 5 years, the SCR in the ChengDa vaccine group gradually decreased to 34.0% at year 5, down from 90.5% at year 1. There was a significant booster effect: the GMT was 15.22 IU/ml on year 5 plus 14 days. Our findings demonstrate that the ChengDa rabies vaccine offers an alternative with a high degree of efficacy and yet limited side effects and ensures that the exposed patient will be on the safe side of the risk of rabies by the 14th day. Moreover, when followed by a booster dose 5 years later, it could boost the immunity. A further booster is effective in inducing a good neutralizing antibody response even after an interval of 5 years.Although effective vaccines for the postexposure treatment of rabies are available (4), there are still about 50,000 to 60,000 human deaths annually. Rabies is a major public health problem in most of the developing world (3, 6). China, the largest developing country in the world, has endeavored tremendously to prevent rabies and manufacture vaccines. In 1981, the Semple vaccine was completely replaced by a locally produced tissue cell vaccine (TCV) in China (15). From 1990 to 1996, numbers of cases of human rabies were extremely low due to the nationwide rabies vaccination program (11), although the numbers of rabies cases increased considerably in recent years, due largely to more relaxed dog control measures. Approximately 5,000,000 persons undergo postexposure rabies vaccination annually (11). China accounts for almost two-thirds of the total postexposure prophylaxis (PEP) used in Asia, and the locally produced tissue culture vaccine is safe and relatively inexpensive (7).Currently, the most prevalently used rabies vaccine in China is the purified Vero cell rabies vaccine (PVRV; Liaoning ChengDa Biological Co., Ltd., Shengyang, China). The Vero cell line has a long and successful history of use for the production of rabies...

Comparison of safety and immunogenicity of purified chick embryo cell vaccine using Zagreb and Essen regimens in patients with category II exposure in China

“…However, there was no significant difference in the seroconversion rates between these 2 groups from day 14, and about 90% of patients had rabies neutralization antibody titers of ≥0.5 IU/mL at day 365 post-immunization. The seroconversion rates are in agreement with our previous study, 11 in which we performed a clinical study with Essen with 5 y of surveillance, and the rates decreased to only 34% at year 5.…”

Immunogenicity, safety and antibody persistence of a purified vero cell cultured rabies vaccine (Speeda) administered by the Zagreb regimen or Essen regimen in post-exposure subjects

“…7,[11][12] Our results confirmed again that a 4-dose regimen was sufficient for RVNA titers to reach effective levels of protection antibody concentrations significantly declined at month 6 and 12, but the percentage of subjects with adequate antibody concentrations in these 2 groups were very close. Essen regimen has been demonstrated the persistence of immunogenicity for up to 5 years, 25 so we speculated Zagreb regimen had good longterm effect. In general, the Zagreb regimen showed a good safety, immunogenicity profile and long-term effects as well as Essen regimen.…”

“…The PVRV for intramuscular pre-and post-exposure rabies prophylaxis manufactured by Chengda Biotechnology has been proven to be well tolerated and immunogenic with an acceptable safety profile in China. [19][20][21][22][23] It has been approved initially by SFDA to use under the Essen regimen in 2005, and permitted to use Zagreb regimen later. Until now, the vaccine has been used 3 million under Zagreb regimen, however, it remained far below than Essen regimen.…”

Monophosphoryl-Lipid A (MPLA) is an Efficacious Adjuvant for Inactivated Rabies Vaccines

“…The absence of or low level of VNA in animals or humans immunized with inactivated rabies vaccines make them susceptible to virulent RABV challenge. Useful adjuvant application or multistep injections of inactivated rabies vaccines could provide enough protection against RABV [48,49]. The World Health Organization (WHO) has recommended a relatively conservative level of 0.5 IU/mL VNA titer for human vaccination [49,50].…”