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At least 109 records · Page 6Linked to original sources
PubMed1996

Ethnic differences in immune responses to hepatitis B vaccine.

A national vaccination program against hepatitis B virus (HBV) to immunize every newborn was initiated in Taiwan in 1986. A serologic survey of 1,812 fully vaccinated children residing in four aboriginal villages and four adjacent nonaboriginal Han Chinese rural villages was conducted in 1993. Children in three of the four aboriginal villages had significantly lower titers of antibody against hepatitis B surface antigen (anti-HBs) than did children in the nonaboriginal villages. Evaluation of cold chain operation for vaccine storage and transport suggested that cold chain failure was not responsible for the fact that children residing in the more remote aboriginal villages had lower mean titers of anti-HBs. However, children whose parents were both aborigines had lower anti-HBs mean titer than did children whose parents were both ethnic Han Chinese. Children of mixed parental origins had intermediate mean titer of anti-HBs. Serologic responses to Japanese encephalitis virus and diphtheria vaccines did not show such correlation with ethnic groups, indicating that the determinant for HBV hyporesponsiveness among the aboriginal children is distinct from that of other childhood vaccines. It was therefore concluded that host factors pertaining to ethnic origin might be responsible for the hyporesponsiveness to HBV vaccine in the aboriginal populations. This finding, if substantiated with further prospective studies, might provide possible means for more targeted trials to improve vaccine response and to reduce vaccine failure among these well-defined ethnic groups.

Child↗
PubMedDate not supplied

[Polymerase chain reaction, cold probes and clinical diagnosis].

Until 1985 the only way to study a gene was to clone it. Henceforth, the polymerase chain reaction (PCR) is an alternative method for synthesizing millions of copies of a specific DNA sequence. Without the development of non radioactive probes, these technologies would have been reserved for research applications. PCR with non radioactive probes is a powerful tool of molecular diagnosis in routine laboratories (identification of viruses and bacteria, diagnosis of human genetic diseases). PCR is based on Taq DNA polymerase. This enzyme is able to polymerize deoxynucleotide precursors (dNTP) in a temperature range of 75-80 degrees C. A typical PCR reaction is a repetitive series of thermic cycles involving template DNA denaturation, oligonucleotide primer annealing, and extension of the annealed primers by DNA polymerase. This three-step process results in the exponential accumulation of a specific fragment whose termini are defined by the 5' end of the primers. Amplification can be estimated to be 2n, where n is the number of cycles. The first step involves denaturation of double-stranded target DNA by heating the sample to 90-95 degrees C. In the second step, the temperature is lowered to about 5 degrees C below the melting temperature of the primer, assuring the specificity of the primer annealing and thus the specificity of the product. The third step is carried out by raising the temperature of the sample to 70-73 degrees C, the optimal temperature for primer extension, involving very little denaturation of the enzyme during the 25-30 cycles of a PCR reaction. The primers used are designed on the basis of the known DNA sequence and they must flank the sequence targeted. For microorganism typing, a product of 300 to 900pb can be amplified, though a 2 kb product can be synthesized. The choice of the primer sequence is a function of the target and technical requirements, such as a GC content of 50-60%, which gives the optimal annealing temperature of 50-55 degrees C. The molecular composition of the primer must be chosen to prevent the formation of intra-molecular secondary structures and primer dimers. The complementarity between the template and the 3' OH end must be perfect, because Taq DNA polymerase activity is markedly lowered by mismatches and secondary structures. The 5' end can thus modified by extension or base modification without altering the quality of the amplification. The yield of the reaction can be modified by the composition of the PCR medium.(ABSTRACT TRUNCATED AT 400 WORDS)

Base Sequence↗
PubMed1990

Vaccination status and seroprevalence of measles and polio antibodies in 1-6-year-old children in the Elim health ward of Gazankulu.

Seroprevalence was used to evaluate the vaccination programme in the Elim health ward of Gazankulu. Antibodies to measles and polio were measured in 1-6-year-old children together with vaccination status. In 224 children studied using a cluster sampling technique, vaccine coverage was found to be 86% for measles and over 90% for polio and diphtheria, pertussis and tetanus. It was difficult to determine vaccine failure rates accurately; 21% of children were seronegative after having received measles vaccine, 32% who had apparently not been vaccinated had antibodies, while a total of 27% had no measles antibodies. Thirty-nine per cent of children failed to demonstrate antibodies to all 3 types of poliovirus after having received 3 doses of oral polio vaccine, 94% had immunity against type 2, and 76% and 74% were immune to types 1 and 3, respectively. Reasons for diminished effectiveness of vaccination programmes are cited; in this study it was probably due to decreased vaccine efficacy related to inadequacies in the cold-chain. Recommendations are that seroprevalence studies are useful, but only after vaccine coverage and the cold-chain have been optimised.

Antibodies, Viral↗
PubMed2000

Extended stability of restriction enzymes at ambient temperatures.

The stability of restriction enzymes as supplied by manufacturers without any modification has been examined. No reduction in activity was observed for three enzymes (HindIII, EcoRI and Tsp509I) held at ambient temperature or 4 degrees C for the period of study (12 months), while activity was observed for up to 12 weeks after storage at 37 degrees C, which was considerably better than following desiccation with trehalose, a recognized preservation technique. A larger trial of 23 different restriction enzymes held at room temperature for one week showed that all enzymes retained significant activity. As a practical demonstration of the usefulness of this finding, enzymes were posted to Africa by conventional mail (cost $1 US) and shown to retain activity upon arrival after three weeks in transit (compared to a cost of $1000 US by cold-chain transportation). Supplying enzymes to third-world markets should now be possible by removing the necessity for cold-chain transport. After arrival, enzymes can simply be stored in a standard domestic refrigerator.

Cold Temperature↗
PubMed2002

Study of operational aspects of pulse polio booths during Intensified Pulse Polio Immunisation Campaign in assembly segments of East Delhi.

The study was undertaken with the objective of observing operational aspects of 609 pulse polio booths established during Intensified Pulse Polio Campaign in East Delhi on National Immunisation Days (NID) during 2001-2002 through well designed format. The average number of persons present on duty at polio booths was 3.73 against a recommendation of 4 per booth. All the booths had vaccine carriers but some of them were not following the guidelines laid for maintaining the cold chain. One sixth "(15.4%)" of the booths needed fresh supplies of vaccine carrier. There is need for deployment of motivated trained manpower at polio booths to ensure the success of Pulse Polio Campaign. Maintenance of cold chain and quality assurance of vaccine administered to children in the field remain a challenge. More than half (55.7%) booths did not have any volunteer. Absence of volunteers from the community in more than half of the booths warrant for strengthening the linkages between the governmental agencies and the community.

Evaluation Studies as Topic↗
PubMed1991

Outbreak of paralytic poliomyelitis in Oman: evidence for widespread transmission among fully vaccinated children.

From January, 1988, to March, 1989, a widespread outbreak (118 cases) of poliomyelitis type 1 occurred in Oman. Incidence of paralytic disease was highest in children younger than 2 years (87/100,000) despite an immunisation programme that recently had raised coverage with 3 doses of oral poliovirus vaccine (OPV) among 12-month-old children from 67% to 87%. We did a case-control study (70 case-patients, 692 age-matched controls) to estimate the clinical efficacy of OPV, assessed the immunogenicity of OPV and extent of poliovirus spread by serology, retrospectively evaluated the cold chain and vaccine potency, and sought the origin of the outbreak strain by genomic sequencing. 3 doses of OPV reduced the risk of paralysis by 91%; vaccine failures could not be explained by failures in the cold chain nor on suboptimum vaccine potency. Cases and controls had virtually identical type 1 neutralising antibody profiles, suggesting that poliovirus type 1 circulation was widespread. Genomic sequencing indicated that the outbreak strain had been recently imported from South Asia and was distinguishable from isolates indigenous to the Middle East. Accumulation of enough children to sustain the outbreak seems to have been due to previous success of the immunisation programme in reducing spread of endemic strains, suboptimum efficacy of OPV, and delay in completing the primary immunisation series until 7 months of age. Additionally, the estimated attack rate of infection among children aged 9-23 months exceeded 25% in some regions, suggesting that a substantial proportion of fully vaccinated children had been involved in the chain of transmission.

Case-Control Studies↗
PubMed2004

Assessment of vaccine wastage during a pulse polio immunization programme in India.

A study to assess the wastage factor of oral polio vaccine (OPV) in the Pulse Polio Immunization (PPI) programme of the Government of India was undertaken by the Indian Council of Medical Research (ICMR) at approximately 31,000 immunization booths all over the country. The study was conducted through the network of 31 Human Reproduction Research Centres (HRRCs) and other ICMR institutes. Wastage at the point of administration of OPV was estimated to be 14.5% with a wastage factor of 1.17 which is well below the assumed wastage of 33% and the corresponding wastage factor of 1.5 in the PPI programme. The wastage and wastage factor as estimated in the present study were also less than the wastage of 25% and the wastage factor of 1.33 recommended by the World Health Organization. Minimum wastage (6.3%) at Kanchipuram and maximum wastage (22.1%) at Kanpur were observed. Further, the wastage of unopened vials and vials during use was also observed following colour changes on the vaccine vial monitor (VVM), indicating poor cold-chain maintenance at the immunization site. In total, 13 booths reported wastage of nine or more unopened vials, whereas 19 booths reported wastage of nine or more vials during use because of colour changes on VVM. Other reasons for wastage of vaccine were also observed from a sample of booths. The technology of introducing VVM on OPV vials for monitoring the cold-chain proved useful in situations in which mass vaccination programmes such as PPI are carried out.

Delivery of Health Care↗
PubMed1994

Progress in the development of a heat-stable recombinant rinderpest vaccine using an attenuated vaccinia virus vector.

Rinderpest is a fatal infectious disease of cattle and buffalo, and is prevalent in many parts of the developing world. Eradication campaigns are at present under way in Africa, the Middle East and South Asia. As these regions have very hot climates, it is difficult and expensive to establish reliable cold chains to deliver heat-sensitive vaccines and, for this reason, many previous vaccination/eradication campaigns have been ineffective. To overcome the problem of vaccine heat-lability, a recombinant rinderpest vaccine (RRV) has been developed by inserting the haemagglutinin gene of rinderpest virus into the attenuated smallpox vaccine (vaccinia virus) and using this as heat-stable vaccine vector system to deliver the foreign antigens. This rinderpest vaccine, as with the smallpox vaccine, could be used for the global eradication campaign, without the need to establish a cold chain. Both the efficacy and the safety of the RRV have been confirmed in experiments in cattle. In addition to heat stability, the RRV has several other advantages over the current rinderpest tissue-culture vaccine. DNA viruses have greater genetic stability than RNA viruses (this may be easily checked by restriction enzyme analysis), and the use of RRV enables vaccinated animals to be distinguished from naturally-infected animals, as the vaccine generates a more restricted antigenic response to rinderpest virus. The current situation in relation to the efficacy and safety of the RRV is discussed.

Animals↗
PubMed1993

A cross-sectional study on vaccine coverage and seroprevalence in schoolchildren in Andorra.

A cross-sectional study on vaccine coverage and vaccine effectiveness was carried out on a randomized sample of the cohort of schoolchildren born in 1983 attending school in Andorra, prior to the introduction of a Systematic Immunisation Plan that included centralised import and delivery of vaccines to vaccinating clinics, surveillance of the cold-chain during vaccine delivery, and a clearly-defined immunization schedule against diphtheria, tetanus, -pertussis, polio, mumps, rubella and measles. Vaccine coverage was estimated from vaccination card records; history of disease and sociodemographic variables were obtained through a questionnaire to the children's parents and vaccine effectiveness was estimated through serum antibody testing. Vaccine coverage levels for DTP and OPV were 97.8% for both. Protective serum antibody prevalence was correspondingly high except for the polio viruses. The authors suggest that decreased vaccine effectiveness, probably due to poor preservation of the cold chain, might be the cause of this finding. In countries or regions with an otherwise developed organisation of health services, an important issue like this can still be overlooked.

Andorra↗
PubMedDate not supplied

[Maximum stability of thermolabile drugs outside the refrigerator].

OBJECTIVE: To review the maximum stability of thermolabile drugs at room temperature (22-25 degrees C) in order to quickly act in case of breakage of the cold chain. METHOD: The study included all drugs available in the pharmacy service from August 17, 2004 to October 15 of the same year, date in which the review was performed, that had to be kept at a temperature ranging between 2 degrees and 8 degrees C. Different drug laboratories were contacted and asked for written information on the matter. RESULTS: The results are reported in a table. One hundred seventy three medicinal products including 83 drugs were reviewed. CONCLUSIONS: Some information provided by the pharmaceutical industry allows the use of drugs even when the cold chain has been broken. This information must be used only in isolated cases, not as a routine.

Drug Stability↗
PubMed2003

Single-dose versus multi-dose vaccine vials for immunization programmes in developing countries.

Excessive vaccine wastage and safety concerns have prompted the international health community to develop and supply vaccines in formats other than the standard multi-dose vial. This article presents a programmatic and economic comparison of the major differences between the multi-dose vials and single-dose formats used for immunization services in developing countries. Multi-dose vials, in general, sell at a lower per-dose price and occupy less cold-chain capacity than single-dose formats. However, higher wastage rates may offset these benefits, especially for more expensive vaccines. Single-dose formats offer several important programmatic benefits, such as increased vaccination opportunities and improved vaccine safety. One single-dose format, the prefilled auto-disable (AD) device, provides additional injection safety and convenience features because it physically combines the vaccine and AD syringe. Selecting the appropriate vaccine presentation will depend on many factors. However, multi-dose vials are likely to be most appropriate for cheaper vaccines and in settings where cold-chain storage capacity is restricted. Single-dose formats will be most appropriate for more expensive vaccines and where there are problems with unsafe injection practices. Prefilled AD injection devices will be particularly useful in expanding outreach services while eliminating the possibility of needle reuse.

Developing Countries↗
PubMed1996

Stabilization of rinderpest vaccine by modification of the lyophilization process.

Rinderpest (RP), a lethal disease of cattle, was almost eradicated from the African continent under Joint Project 15 (JP15), using an excellent modified live virus vaccine. Due to marked instability of the vaccine, a cold chain was required to ensure that the vaccine was potent at the time of application. Rinderpest re-emerged in the early 1980s. The Pan African Rinderpest Campaign (PARC) was developed to combat the new epidemic. For PARC to be efficacious and affordable, there was a clear need to have a vaccine that was thermostable. The need for a stable vaccine was underscored in politically unstable areas such as the Sudan, where the veterinary infrastructure has diminished and vaccination has been left in the hands of personnel who must act expeditiously. This paper reviews studies on various stabilizers and a modified lyophilization cycle that resulted in a highly thermostable RP vaccine. The useful shelf life of the vaccine, under African field conditions, was increased from less than one week to at least 100 days. For practical reasons, PARC recommends that the vaccine be used within 30 days of leaving refrigeration (the cold chain).

Africa↗
PubMed2005

Development of a novel microbial sensor with baker's yeast cells for monitoring temperature control during cold food chain.

A novel microbial sensor containing a commercial baker's yeast with a high freeze tolerance was developed for visibly detecting inappropriate temperature control of food. When the yeast cells fermented glucose, the resulting gas production triggered the microbial sensor. The biosensor was a simple, small bag containing a solution of yeast cells, yeast extract, glucose, and glycerol sealed up with multilayer transparent film with barriers against oxygen and humidity. Fine adjustment of gas productivity in the biosensor at low temperatures was achieved by changing either or both concentrations of glucose and yeast cells. Moreover, the amount of time that food was exposed to inappropriate temperatures could be deduced by the amount of gas produced in the biosensor. The biosensor was stable without any functional loss for up to 1 week in frozen storage. The biosensor could offer a useful tool for securing food safety by maintaining low-temperature control in every stage from farm to fork, including during transportation, in the store, and at home.

Biosensing Techniques↗
PubMedDate not supplied

[Potential validity of thermolabile drugs outside the preservation conditions recommended by the manufacturer].

Hospital pharmacists, according to the Ley del Medicamento 25/1990 of 20th December, should ensure appropriate drug preservation within the Pharmacy Department and in hospital stocks. The storage and preservation of thermolabile drugs according to manufacturer recommendations guarantees stability and optimal use conditions until the expiration date. Cold chain disruption may significantly affect the activity and toxicity of these drugs. Pharmacists should make quick decisions in case of cold chain-related events, hence the relevance of up-to-date information on stability under temperatures differing from those recommended. A review of the information available on the stability of drugs commonly used in the hospital setting that require a fridge for storage has been carried out.

Drug Stability↗
PubMed2006

Improving birth dose coverage of hepatitis B vaccine.

Administration of a birth dose of hepatitis B vaccine (HepB vaccine) to neonates is recommended to prevent mother-to-infant transmission and chronic infection with the hepatitis B virus (HBV). Although manufacturers recommend HepB vaccine distribution and storage at 2-8 degrees C, recognition of the heat stability of hepatitis B surface antigen stimulated research into its use after storage at, or exposure to, ambient or high temperatures. Storage of HepB vaccine at ambient temperatures would enable birth dosing for neonates delivered at home in remote areas or at health posts lacking refrigeration. This article reviews the current evidence on the thermostability of HepB vaccine when stored outside the cold chain (OCC). The reports reviewed show that the vaccines studied were safe and effective whether stored cold or OCC. Field and laboratory data also verifies the retained potency of the vaccine after exposure to heat. The attachment of a highly stable variety of a vaccine vial monitor (measuring cumulative exposure to heat) on many HepB vaccines strongly supports policies allowing their storage OCC, when this will benefit birth dose coverage. We recommend that this strategy be introduced to improve birth dose coverage, especially in rural and remote areas. Concurrent monitoring and evaluation should be undertaken to affirm the safe implementation of this strategy, and assess its cost, feasibility and effect on reducing HBV infection rates. Meanwhile, release of manufacturer data verifying the potency of currently available HepB vaccines after exposure to heat will increase confidence in the use of vaccine vial monitors as a managerial tool during storage of HepB vaccine OCC.

Drug Storage↗
PubMed1980

Structural studies of the sugar chains of cold-insoluble globulin isolated from human plasma.

The asparagine-linked sugar chains of cold-insoluble globulin isolated from human plasma were released as oligosaccharides from the polypeptide moiety by hydrazinolysis. These oligosaccharides were N-acetylated and could be labeled by reduction with NaB[3H]4. The yield of radioactive oligosaccharides indicated that the glycoprotein has four asparagine-linked sugar chains in one molecule. More than 90% of the radioactive oligosaccharides contain N-acetylneuraminic acid, and could be separated into two acidic oligosaccharides, A-1 and A-2. By sequential exoglycosidase digestion in combination with methylation studies, their structures were elucidated as Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3) Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc and NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6 (NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2 Man alpha 1 leads to 3)-Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc.

Carbohydrate Sequence↗