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At least 19 recordsLinked to original sources
PubMed2004

Collaborative study to assess the suitability of a candidate International Standard for yellow fever vaccine.

Yellow fever vaccines are routinely assayed by plaque assay. However, the results of these assays are then converted into mouse LD(50) using correlations/conversion factors which, in many cases, were established many years ago. The minimum required potency in WHO Recommendations is 10(3) LD(50)/dose. Thirteen participants from 8 countries participated in a collaborative study whose aim was to assess the suitability of two candidate preparations to serve as an International Standard for yellow fever vaccine. In addition, the study investigated the relationship between the mouse LD(50) test and plaque forming units with a view to updating the WHO recommendations. Plaque assays were more reproducible than mouse assays, as expected. Differences in sensitivities of plaque assays were observed between laboratories but these differences appear to be consistent within a laboratory for all samples and the expression of potency relative to the candidate standard vaccine improved the reproducibility of assays between laboratories. However, the use of potencies had little effect on the between laboratory variability in mouse LD(50) assays. There appears to be a consistent relationship between overall mean LD(50) and plaques titre for all study preparations other than sample E. The slope of the correlation curve is >1 and it would appear that 10(3) LD(50) is approximately equivalent to 10(4) plaque forming units (PFU), based on the overall means of all laboratory results. The First International Standard for yellow fever vaccine, NIBSC Code 99/616, has been established as the First International Standard for yellow fever vaccine by the Expert Committee of Biological Standards of the World Health Organisation. The International Standard has been arbitrarily assigned a potency of 10(4.5) International Units (IU) per ampoule. Manufacturers and National Control Laboratories are including the First International Standard for yellow fever vaccine in routine assays so that the minimum potency in IU of vaccines released for use and which meet the current minimum potency of 10(3) LD(50) in mouse assays, can be determined. These data will be analysed before a review of the WHO requirements, including the minimum potency per dose, is undertaken.

Animals↗
PubMed1996

Stability of yellow fever vaccine.

Yellow fever, an acute mosquito-borne viral haemorrhagic fever, is preventable by use of the live, attenuated 17D vaccine. The vaccine is used principally in tropical climates and is subject to potentially adverse conditions. Lyophilized vaccine without stabilizers deteriorates rapidly when exposed to temperatures above -20 degrees C. In 1987, the WHO recommended that each lot of vaccine meet the following stability test: maintenance of potency (> 1,000 mouse i.c.LD50/human dose) with mean loss of titre < 1.0 log10 after being held at 37 degrees C for 14 days. In 1987, only 5 out of 12 yellow fever vaccines produced worldwide met the stability standards. To improve stability of the vaccine, a number of additives have been systematically investigated. A successful formulation, now used by a number of manufacturers, employs sugars, amino acids, and divalent cations [lactose (4%), sorbitol (2%), histidine (0.01 M), alanine (0.01 M), in phosphate buffered saline with Ca2+ and Mg2+]. As opposed to vaccine produced without stabilizers, which loses 1.5-2.5 log10/dose, stabilized vaccines lose only 0.3-0.5 log10 after being held at 37 degrees C for 14 days. The vaccine is stable after storage for > or = two years at 4 degrees C and 22 degrees C, and has a stability profile as good or better than many other live and inactivated vaccines currently used in the EPI, including measles, pertussis, oral and inactivated poliomyelitis vaccines. WHO is taking steps to enssure that all 11 current YF vaccine manufacturers produce vaccines that meet accepted stability standards. The principal rationale for increasing 17D vaccine stability beyond that achieved with the present stabilizers would be the improvement in stability of other EPI vaccines, to the point where yellow fever vaccine was the most sensitive vaccine among those deployed. The acceptable characteristics of current stabilized 17D vaccines and the high cost of changing and validating new vaccine formulations precludes a major investment at this time. Despite its stability when freeze dried, yellow fever 17D vaccine is quite unstable after reconstitution and must be discarded after one hour. Improvement in vaccine stability after reconstitution would thus reduce cost, stretch supplies of vaccine, and ensure against vaccine failures due to use of degraded vaccine. This is an area for future research.

Animals↗
PubMed2004

Current status of the Arilvax; yellow fever vaccine.

Yellow fever is a viral hemorrhagic fever that involves dysfunction of the liver and kidneys. There is no antiviral therapy available and vaccination is a major strategy in the control of this important public health problem. Yellow fever vaccine is a live attenuated vaccine, strain 17D, which is very safe and efficacious and induces long-term protective immunity in vaccinees. The vaccine is produced by six manufacturers worldwide, including Arilvax by Chiron vaccines (CA, USA) that is marketed in at least ten countries. Acambis (MA, USA) have acquired the rights to sell and market Arilvax in the USA, and have undertaken three clinical trials to obtain data for a Biological License Application that should proceed in 2005.

Clinical Trials, Phase III as Topic↗
PubMed2000

Stability-related studies on 17D yellow fever vaccine.

Yellow fever (YF) vaccine using the 17D strain of YF attenuated virus has been produced at the Institut Pasteur in Dakar since 1962. Until now, the stabilised YF had an expiry date of utilization of two years from the end of the lot control process under storage at +4 degrees C. We conducted a stability study to assess the three full year validity of this preparation, when correctly stored at +4 degrees C to optimise the conditions of production, storage and availability of such a vaccine. The activity of 19 consecutive batches of vaccines kept for three years at +4 degrees C was compared to that of the same batches that were kept three years at -20 degrees C. Using the in vitro microculture method, we found that three-year storage at +4 degrees C induced a higher loss of activity than storage at -20 degrees C or than the accelerated degradation test of vaccines kept for 14 days at 37 degrees C. Whatever the conditions of storage, in all cases decreases in activity were below the WHO's requirements, i.e., < 1 log PFU/dose, and residual activity of the selected batches was over 1000 mouse LD50 per dose. We demonstrated that the 17D YF vaccine produced in Dakar has a shelf-life of three years and that its required potency was maintained at +4 degrees C, after reconstitution with saline diluent, following three-year storage at +4 degrees C.

Animals↗
PubMed2004

Risk of fatal adverse events associated with 17DD yellow fever vaccine.

Yellow fever (YF), an acute infectious disease, is endemic in the north and central-west of Brazil. This disease can be prevented by the use of a vaccine. In Brazil, four fatal adverse events have been associated with the YF vaccine used in the country (17DD vaccine). We briefly describe the last two fatalities, and estimate the risk of 17DD-associated fatal adverse events under different epidemiological scenarios. Controversies regarding the appropriate denominator that enters the estimation of risk serve as a motivation for each proposed scenario. The statistical procedures used show optimum behaviour when assessing the risk of rare events. Risk estimates vary from 0.043 (95 % CI 0.017-0.110) to 2.131 (95 % CI 0.109-12.071) fatalities per million doses administered. The robust estimates of the risk of fatal adverse events we present constitute an important element in future risk-benefit analysis and point to the need for good quality vaccine coverage and adverse-events surveillance data to assess the risk of vaccination. Although vaccination of YF endemic regions is necessary to maintain low disease prevalence, preventive administration of YF vaccine to the entire population should be cautiously analysed.

Adult↗
PubMed2005

Yellow fever vaccine.

Yellow fever, a mosquito-borne viral hemorrhagic fever, is one of the most lethal diseases of humankind. The etiologic agent is the prototype member of the genus Flavivirus, family Flaviviridae, a group of small, enveloped, positive-sense, single-strand RNA viruses. Approximately one in seven people who become infected develop a rapidly progressive illness, with hepatitis, renal failure, hemorrhage and cardiovascular shock, with a case fatality rate of 20-50%. Yellow fever occurs in sub-Saharan Africa and tropical South America, where it remains a continuing public health problem of varying magnitude, depending on the level of vaccination coverage in the human population and cyclical, ecologic and climatic factors that influence virus transmission.

Animals↗
PubMed2004

Current Assessment of Yellow Fever and Yellow Fever Vaccine.

Yellow fever (YF) is a mosquito-borne viral illness that causes hemorrhagic fever in tropical Africa and South America. Although a very safe and efficient vaccine (17D) is available, it is underused. An estimated 200,000 people are still infected annually, and YF remains a major public health concern. This article reviews the recent data on YF epidemiology, virology, and immunity, and analyzes the rare postvaccination adverse effects that have been recently reported. YF vaccine should be included in the expanded program of immunization for children and sustained for people living in or traveling to endemic areas. A surveillance of vaccinated people also should be reinforced. New research programs should be developed to identify molecular markers of YF virus tropism and attenuation, and to understand mechanisms of host responses to virus infection.

Journal Article↗
PubMed2004

Viscerotropic and neurotropic disease following vaccination with the 17D yellow fever vaccine, ARILVAX.

Yellow fever vaccine associated viscerotropic (YFV-AVD) and neurotropic (YFV-AND) diseases have been recently identified in various countries. Previously post-vaccination multiple organ system failure was recognised as a rare serious adverse event of yellow fever vaccination and 21 cases of post-vaccinal (YFV) encephalitis had been recorded. Incidence data is not available. On investigation of vaccine surveillance reports from Europe following distribution of more than 3 million doses of ARILVAX trade mark, four cases each of YFV-AVD and YFV-AND were found (each 1.3 cases per million doses distributed) for the period 1991 to 2003. The incidence for each is higher after 1996 (2.5 cases per million doses distributed). The incidence of these adverse events appears to be very low with ARILVAX trade mark. Similar incidence data is required from other countries for comparison.

Encephalomyelitis, Acute Disseminated↗
PubMed1997

Safety and immunogenicity of live oral cholera and typhoid vaccines administered alone or in combination with antimalarial drugs, oral polio vaccine, or yellow fever vaccine.

The effects of concomitant administration of antimalarial drugs, oral polio vaccine, or yellow fever vaccine on the immune response elicited by the Vibrio cholerae CVD103-HgR and Salmonella typhi Ty21a live oral vaccines were investigated. Healthy adults were immunized with CVD103-HgR alone or combined with Ty21a. Subjects were randomized to simultaneously receive mefloquine, chloroquine or proguanil, or oral polio or yellow fever vaccine. The vibriocidal antibody seroconversion rate was significantly reduced (P = .008) only in the group that received chloroquine with the CVD103-HgR. The geometric mean vibriocidal antibody titer was significantly decreased in the groups that received chloroquine (P = .001) or mefloquine (P = .02) compared with titers in groups that received CVD103-HgR alone. However, similar immunosuppressive effects were not observed in the groups immunized with Ty21a and CVD103-HgR. Only the concomitant administration of proguanil effected a significant (P = .013) decline in the anti-S. typhi lipopolysaccharide antibody response. These results indicate that chloroquine and proguanil should not be simultaneously administered with the CVD103-HgR and Ty21a vaccine strains, respectively.

Administration, Oral↗
PubMed2001

Hepatitis and death following vaccination with 17D-204 yellow fever vaccine.

We describe a man vaccinated with the 17D204 strain of yellow fever virus, who subsequently died of yellow fever. Sequencing of the NS5-39 untranslated region showed that the virus isolated from the patient was identical to the vaccine strain of the same batch, and different from wild-type virus. Both viruses contained a mutation, although the association of this mutation with virulence is unknown. Severe, rapidly progressive, and ultimately fatal disease can follow use of the 17D204 vaccine strain. There is need for renewed discussion as to the safety of the vaccine and the indications for its use.

Adverse Drug Reaction Reporting Systems↗
PubMed1989

Association of IDDM and attenuated response of 2',5'-oligoadenylate synthetase to yellow fever vaccine.

Basal and yellow fever vaccination-induced 2',5'-oligoadenylate synthetase (2',5'A) activity was determined in blood mononuclear cells (peripheral blood lymphocytes [PBLs]) from insulin-dependent diabetes mellitus (IDDM) and matched control subjects. The live attenuated yellow fever vaccine represented a primary stimulus in all subjects. First, basal 2',5'A activity increased severalfold in response to yellow fever vaccination. In IDDM subjects, this increase was significantly lower (P = .025). Second, the 2',5'A activity increased proportionately to the higher basal 2',5'A activity in IDDM subjects. In control subjects, the increase in 2',5'A activity was not dependent on the basal activity. There was no relationship between basal or stimulated 2',5'A activity and age, sex, duration of IDDM, age at onset of IDDM, metabolic control, or HLA-DQ beta-chain gene polymorphism. There is a direct relationship between 2',5'A activity and latent viral infections associated with the presence of double-stranded RNA and with cellular interferons (IFNs) formed in response to viral infections. The higher basal 2',5'A activity (P = .05) in relation to the stimulated activity may therefore signify a latent infection or the presence of double-stranded RNA in PBLs of IDDM subjects. In vitro stimulation of PBLs showed increased IFN sensitivity in IDDM subjects. Analysis of 2',5'A activity is proposed to be a sensitive measure of the activation of the IFN system and the level of latent infectivity.

2',5'-Oligoadenylate Synthetase↗
PubMed2006

Neutralizing antibody response to booster vaccination with the 17d yellow fever vaccine.

A retrospective review was conducted of yellow fever vaccination among laboratory workers receiving annual serologic assessment to determine the initial and long-term response after boosting. Patients were divided into three groups based on pre-vaccination serology: Group 1, 1:10; Group 2, 1:20-1:40 and Group 3, >1:40. The percent with > or = four-fold increase in titers after booster vaccination were: 78% (646/829, Group 1), 65% (79/121, Group 2) and 10% (8/79, Group 3) (p<0.0001). The median times to titer failure (<1:40) were 798 days (Group 1), 3340 days (Group 2) and 7709 days (Group 3) (p<0.0001). Pre-vaccination serology influenced the initial and long-term response to yellow fever booster vaccination.

Adult↗