Maintenance Of Cold Chain Research Articles

Consumer link in cold chain: Indian scenario

This paper is an attempt to study the awareness, behavior and practices among Indian consumers, regarding maintenance of cold chain from retailer’s place to home and at homes within the framework of food safety. A sample of 524 consumers is taken in total. The study is conducted at 12 retail stores and through household visits in three state capitals in India. The study reveals that the consumers do not have adequate awareness about refrigeration practices or consider themselves responsible for maintaining cold chain and food safety. At a time when cold chain is a key issue for the food industry, these findings could assist government, non-government organizations, industry, academia and community in collectively developing effective public education programs, to alert and motivate the consumers against the possible hazards of ignorance of healthy practices for cold chain maintenance at homes.

Quality assessment of child care services in primary health care settings of Central Karnataka (Davangere District)

Background:Infectious disease and malnutrition are common in children. Primary health care came into being to decrease the morbidity. Quality assessment is neither clinical research nor technology assessment. It is primarily an administrative device used to monitor performance to determine whether it continues to remain within acceptable bounds.Aims and Objectives:To assess the quality of service in the delivery of child health care in a primary health care setting. To evaluate client satisfaction. To assess utilization of facilities by the community.Materials and Methods:Study Type: Cross-sectional community-based study. Quality assessment was done by taking 30-50%, of the service provider. Client satisfaction was determined with 1 Immunization and child examination-90 clients each. Utilization of services was assessed among 478 households.Statistical Analysis:Proportions, Likert's scale to grade the services and Chi-square.Results:Immunization service: Identification of needed vaccine, preparation and care was average. Vaccination technique, documentation, EPI education, maintenance of cold chain and supplies were excellent. Client satisfaction was good. Growth monitoring: It was excellent except for mother's education andoutreach educational session. Acute respiratory tract infection care: History, physical examination, ARI education were poor. Classification, treatment and referral were excellent. Client satisfaction was good. Diarrheal disease care: History taking was excellent. But examination, classification, treatment, ORT education were poor.Conclusion:Mothers education was not stressed by service providers. Service providers’ knowledge do not go with the quality of service rendered. Physical examination of the child was not good. Except for immunization other services were average.

Transfusion transmitted infections: How many more?

Transfusion transmitted infections (TTI) are a great concern of safety for patients. Since the starting of blood transfusion scientifically in the early 1940s, various transfusion associated problems have come to the forefront for the scientific community. These include TTI, alloimmunization to various blood components, issues related to cold chain maintenance, platelet refractoriness, transfusion (iron) overload, transfusion associated graft versus host diseases (GvHD), immunomodulatory effects, etc. However, TTI was first observed in the process of blood transfusion in the late 1940s. Till early 1970s, blood bank personnel were only concentrating on a few blood borne infections like syphilis and serum hepatitis by “Australia antigens”. However, the scientific community was well aware that there would be multiple agents.

Monitoring of mass measles campaign in AILA-affected areas of West Bengal

A mass measles campaign was organized in AILA-affected areas of West Bengal in July-August 2009. The present cross-sectional study was conducted with the objectives to monitor and assess the cold chain maintenance, safe injection practices, IEC methods adopted, and to observe the conduction of the sessions in the campaign. All the cold chain points at the block level had adequate vaccines and equipments, twice monitoring of temperature which was in optimal range. 82% sessions had team according to microplan, AWW was present and team members were actively mobilizing the children in 83% sessions, puncture proof container was used and vaccines were given in correct sites in more than 95% sessions. The study observed satisfactory conduction of the whole campaign, still the injection safety procedures should be strengthened considering the potential harm to the health care providers.

Toward the development of a stable, freeze-dried formulation of Helicobacter pylori killed whole cell vaccine adjuvanted with a novel mutant of Escherichia coli heat-labile toxin

No vaccine exists for the prevention of infection with the ubiquitous gastric pathogen Helicobacter pylori, and drug therapy for the infection is complicated by poor patient compliance, the high cost of treatment, and ineffectiveness against drug-resistant strains. A new medical advancement is required to reduce the incidence of peptic ulcer disease and stomach cancer, two conditions caused by infection with H. pylori. Clinical trials have been performed with a formalin-inactivated H. pylori whole cell (HWC) vaccine, given orally in combination with the mucosal adjuvant mLT(R192G), a mutant of Escherichia coli heat-labile toxin. Following the initial dose of this vaccine, some subjects experienced gastrointestinal side effects. To reduce side effects and potentially further increase the amount of adjuvant that can safely be administered with the HWC vaccine, experiments were performed with a form of LT that carried two mutations in the A subunit, a substitution of G for R at position 192, and A for L at position 211. The double mutant LT (dmLT) adjuvant stimulated immune responses as effectively as the single mutant LT in mice. Additionally, following a challenge infection, the dmLT-adjuvanted vaccine was as effective as single mutant LT in reducing gastric urease levels (diagnostic for H. pylori infection), and H. pylori colonization in the stomach as assessed by quantitative analysis of stomach homogenates. A lyophilized formulation of HWC was developed to improve stability and to potentially reduce reliance on cold chain maintenance. It was observed that a dmLT-adjuvanted lyophilized vaccine was equally as protective in the mouse model as the liquid formulation as assessed by gastric urease analysis and analysis of stomach homogenates for viable H. pylori. No readily detectable effect of tonicity or moisture content was observed for the lyophilized vaccine within the formulation limits evaluated. In an accelerated stability study performed at 37 °C the lyophilized vaccine remained equally as protective as vaccine stored at 2–8 °C. The formulation selected for clinical development consisted of 2.5 × 10 10 formalin-inactivated cells per ml in 6.5% trehalose, 0.5% mannitol, and 10 mM citrate buffer at pH 6.8.

Role of heavy water in biological sciences with an emphasis on thermostabilization of vaccines

Preservation of vaccines, viruses and other biologicals is one of the onerous tasks in maintaining the quality of the products from manufacture until they reach the end users. Live-attenuated viral vaccines, serum immunoglobulins, plasma fractions and clinical samples, including tissues and body fluids, are all materials that usually require cold-chain maintenance during storage and distribution. A number of stabilizers are currently used to help retain the quality of these materials, in particular vaccines, during transit. Deuterium oxide (heavy water; D2O) has previously been reported to have a protective effect on biomolecules (proteins and nucleic acids), cells and simple multicellular organisms against thermal shock. Of late, the potential of D2O has been demonstrated in stabilization of the oral polio and yellow fever 17D vaccines. This review is the outcome of a thorough search and scan of the literature in a quest to explore the potential use of heavy water in the stabilization of veterinary biologicals. The literature search revealed this potential of heavy water as exemplified by successful stabilization of oral polio and yellow fever vaccines. Through this review, the authors wish to inform animal health researchers and disseminate their knowledge on the use of heavy water in biomolecule stabilization and its potential application in the stabilization of veterinary vaccines and other biologicals.

Introducing HPV Vaccine in Developing Countries - Addressing the Challenge.

Sir, Vaccines have played a crucial role in preventing infectious disease-associated morbidity and mortality, worldwide. Vaccinations have achieved several milestones e.g. eradication of smallpox, imminent eradication of polio, and a dramatic reduction in the prevalence of childhood infections like diphtheria, tetanus and pertusis. Many newer, safe and effective vaccines, like those against Hib, Pneumococcus, Hep A, Chicken pox, Rotavirus, HPV to name a few, are only now making an entry into the market of developing countries, though they were introduced decades earlier in the developed countries.(1) Current findings based on results from clinical trials indicate that a three-dose schedule of both bivalent and quadrivalent vaccine formulations against HPV are highly immunogenic with sero-conversion rates to all targeted HPV types of over 98%.(2) However, the mere availability of an effective vaccine is not synonymous with an effective vaccination program. Challenges to the introduction of HPV vaccine in our country: Relatively high cost of HPV vaccine.(3) How to reach the target population? Coverage with existing EPI vaccines is only 43.5% for fully vaccinated children aged 12-23 months with an estimated 12.5 million under-immunized children each year.(4) Poor healthcare infrastructure, inadequate maintenance of cold chain and injection safety. Limited resources of UIP and competition faced from other newer vaccines like Hib, pneumococcal, rotavirus, meningococcal, JE vaccines etc.(5) Poor success of secondary prevention methods e.g. HPV screening, Pap testing, or visual inspection in the country. Religious barriers, cultural taboos and misconceptions influencing acceptance by doctors, parents, adolescents and public in general e.g. a vaccine targeted primarily to females and associated with a sexually transmitted infection may exacerbate rumors like a plot to sterilize young girls.(5) Lack of political will. Without a doubt, one of the greatest barriers to the introduction of this vaccine is its price.(6) Several mechanisms to make vaccines affordable in the context of developing countries have been proposed, like differential pricing, advance market commitments (AMC) and voluntary and compulsory licensing. The most prominent model is differential (or tiered) pricing, where the patent owner retains production and control of pricing between segmented markets.(7) Proposals based on advanced market commitment provides an assured price subsidy for developing country purchase of a future vaccine meeting predefined standards. This mechanism can provide the industry with greater assurances of earning a reasonable return on their investment and act as a motivation to serve the poorest developing countries.(8) Differential pricing may be combined with donor financing support and advance market commitments. A new type of license that uses market forces to lower prices through generic competition in low and middle-income countries while ensuring that pharmaceutical companies are appropriately reimbursed for their research and development holds much promise.(7) Wider global availability of affordable vaccines can be achieved through building local or regional clinical trial and vaccine production capacity.(1) Hepatitis B vaccine production in South Korea was a major factor in bringing the price of this vaccine to affordable levels in the developing world.(5) Countries can use the established immunization networks or networks of Sexual and Reproductive Health (SRH) services such as family planning, pre- and post-natal care or a mixture of systems to deliver the vaccine to the target population. Immunization service delivery is the most successful public health system in the world and the infrastructure of trained staff, cold chain and logistics, clinics and outreach services, and information systems is a resource that could be utilized to deliver HPV vaccine.(5) The immunization system will need to be substantially enlarged to reach large numbers of adolescents and women of child-bearing age outside the ambit of pre-natal services.(5) Local logistical hurdles must be overcome and the opportunity of strengthening health care infrastructure through vaccination must be utilized.(1) SRH services could simultaneously provide important contacts for health education and advocacy for HPV and dispel myths and misconceptions regarding the vaccination. Ultimately, the decision of whether and when a vaccine will be introduced will depend on individual countries. To prepare for decisions on HPV vaccine use, the sexual and reproductive health (SRH; including adolescent health), immunization, and cancer control communities need to work together to analyze the appropriate data and build international and national consensus.(5) Local leaders must be convinced of the benefits of vaccination to make immunization a high priority. Finally, ‘translational research’ can provide the answer to rational introduction of newer vaccines like HPV in developing countries for optimum utilization of available resources.(9)

Pre-clinical evaluation of a novel nanoemulsion-based hepatitis B mucosal vaccine.

BackgroundHepatitis B virus infection remains an important global health concern despite the availability of safe and effective prophylactic vaccines. Limitations to these vaccines include requirement for refrigeration and three immunizations thereby restricting use in the developing world. A new nasal hepatitis B vaccine composed of recombinant hepatitis B surface antigen (HBsAg) in a novel nanoemulsion (NE) adjuvant (HBsAg-NE) could be effective with fewer administrations.Methodology and Principal FindingsPhysical characterization indicated that HBsAg-NE consists of uniform lipid droplets (349+/−17 nm) associated with HBsAg through electrostatic and hydrophobic interactions. Immunogenicity of HBsAg-NE vaccine was evaluated in mice, rats and guinea pigs. Animals immunized intranasally developed robust and sustained systemic IgG, mucosal IgA and strong antigen-specific cellular immune responses. Serum IgG reached ≥106 titers and was comparable to intramuscular vaccination with alum-adjuvanted vaccine (HBsAg-Alu). Normalization showed that HBsAg-NE vaccination correlates with a protective immunity equivalent or greater than 1000 IU/ml. Th1 polarized immune response was indicated by IFN-γ and TNF-α cytokine production and elevated levels of IgG2 subclass of HBsAg-specific antibodies. The vaccine retains full immunogenicity for a year at 4°C, 6 months at 25°C and 6 weeks at 40°C. Comprehensive pre-clinical toxicology evaluation demonstrated that HBsAg-NE vaccine is safe and well tolerated in multiple animal models.ConclusionsOur results suggest that needle-free nasal immunization with HBsAg-NE could be a safe and effective hepatitis B vaccine, or provide an alternative booster administration for the parenteral hepatitis B vaccines. This vaccine induces a Th1 associated cellular immunity and also may provide therapeutic benefit to patients with chronic hepatitis B infection who lack cellular immune responses to adequately control viral replication. Long-term stability of this vaccine formulation at elevated temperatures suggests a direct advantage in the field, since potential excursions from cold chain maintenance could be tolerated without a loss in therapeutic efficacy.

Heat resistance of Bacillus cereus emetic toxin, cereulide

The study describes the effects of heating temperature and exposure time on the thermal stability of cereulide under different conditions (pH, presence/absence of oil phase and cereulide concentration). Cereulide heat inactivation was investigated at 100, 121 and 150 degrees C under different alkaline pH values (8.6-10.6) and in the presence of oil phase (0.6-1.4%). Three different cereulide concentrations (0.5, 5 and 6 microg ml(-1)) were used. Cereulide detection was performed with computer-aided semen analyzer and with HPLC-MS. Highly alkaline pH was needed to achieve inactivation. At lower cereulide concentrations less drastic conditions were needed. Removal of alkaline buffer after the heat treatment resulted in the recovery of toxic activity. Heat stability of cereulide has been proved to be remarkable, even at highly alkaline pH values, at all temperatures tested. The loss of activity appeared to be reversible. The study demonstrates the inability of any heat treatment used in the food industry to inactivate cereulide. Food safety has to rely on prevention and cold chain maintenance. Cleaning practices also need to be adapted as cereulide may remain in its active form upon sterilization of used material.

Surveillance of cold chain system during Intensified Pulse Polio programme-2006 in Chandigarh

To evaluate the maintenance of cold chain system in the Intensive Pulse Polio Immunization (IPPI) campaign in the Union Territory, Chandigarh. A cross sectional study was conducted in 18 designated vaccine sub-depots, where OPV vials were stored prior to IPPI and 25 IPPI booths out of the designated 406 IPPI booths in U.T, Chandigarh. The booths were selected by stratified random sampling technique. 25 Vaccine vials, one from each booth were selected and sent for potency testing at Central Research Institute (CRI)-Kasauli. All the randomly selected vaccine samples were reported portent, as per the reports provided by CRI-Kasauli. Cold chain maintenance and temperature charting was found satisfactory. There are some avoidable errors which leaves room for improvement, which can be in the form of provision of adequate number of exhaust fan, voltage stabilizers, etc. Uninterrupted power supply should be ensured. Lastly, more emphasis is to be given on maintenance of cold chain system in reorientation training program of all health functionaries.

Relationship between vaccine vial monitors and cold chain infrastructure in a rural district of India

The potency of oral polio vaccine (OPV), a heat-labile vaccine, is preserved by the cold chain. The Vaccine Vial Monitor, a heat-sensitive label, is critical to the monitoring and maintenance of the cold chain. This study was conducted to evaluate the relationship between the adequacy of cold chain infrastructure and the proper use of Vaccine Vial Monitor in a rural district of India. Forty-six health centers in a rural district were included in our evaluation of the cold chain equipment and the Vaccine Vial Monitors. Cold chain equipment and vaccine vials within each health center were evaluated for adherence to WHO cold chain maintenance protocols and the Vaccine Vial Monitor stage, respectively. Among the 46 health centers, Vaccine Vial Monitor stage I was found at 58% of the health centers, 33% of the health centers reported stage II and 9% reported a stage III, indicating weaknesses in the cold chain mechanism Cold chain for the OPV was not adequately maintained at primary and sub-health centers in this rural district. Well maintained ice packs and vaccine carriers will help ensure delivery and availability of a safe and potent vaccine to children in rural areas of India.

An assessment of the compliance with good pharmacy practice in an urban and rural district in Sri Lanka

To evaluate the compliance of private pharmacies to good pharmacy practice (GPP) in an urban and rural district in Sri Lanka and identify deficiencies with a view to improving supply of safe and effective drugs to consumers. Lot quality assurance sampling (LQAS) method was used to determine the number of pharmacies that need to be studied and the threshold limit of defective elements. An inspection of 20 pharmacies in the urban and all 18 pharmacies in the rural district was carried out using a structured checklist. Compliance to seven subsystems of GPP was studied. Storage of drugs, maintenance of cold chain, dispensing and documentation were comprehensively substandard in both districts. Individual items of supervision in registration, physical environment and order of the pharmacy were also found to be substandard in both districts. This study shows that the LQAS method can be used to identify inadequate pharmacy services in the community as a whole. There was poor compliance to GPP by the private pharmacies in both districts. There are concerns about the quality of drugs and the safety of private pharmacy services to the community. Some of the deficiencies could be easily corrected by educating the pharmacists and authorised officers, and more effective and streamlined supervision.

INCREASING FOOD AVAILABILITY BY REDUCING POSTHARVEST LOSSES OF FRESH PRODUCE

Qualitative losses (such as loss of caloric and nutritive value, loss of acceptability by consumers, and loss of edibility) are more difficult to measure than quantitative losses of fresh fruits and vegetables. While reduction of quantitative losses is a higher priority than qualitative losses in developing countries, the opposite is true in developed countries where consumer dissatisfaction with produce quality results in a greater percentage of the total postharvet losses. Providing consumers with fruits and vegetables that taste good can greatly increase their consumption of the recommended minimum of five servings per day for better health. Development of new cultivars with better flavor and nutritional quality plus adequate productivity should be given high priority in all countries. Strategies for reducing postharvest losses in developing countries include: (1) Application of current knowledge to improve the handling systems (especially packaging and cold chain maintenance) of horticultural perishables and assure their quality and safety; (2) Overcoming the socioeconomic constraints, such as inadequacies of infrastructure, poor marketing systems, and weak RD and (3) Encouraging consolidation and vertical integration among producers and marketers of horticultural crops. ESTIMATION OF POSTHARVEST LOSSES Both quantitative and qualitative losses occur in horticultural crops between harvest and consumption. Our goal is to minimize these losses, and to do so we must: 1) understand the biological and environmental factors involved in postharvest deterioration, and 2) use the appropriate postharvest technology procedures that will slow down deterioration and maintain quality and safety of the commodities. Qualitative losses, such as loss in edibility, nutritional quality, caloric value, and consumer acceptability of the products, are much more difficult to assess than quantitative losses. Standards of quality and consumer preferences and purchasing power vary greatly among countries and cultures. For example, elimination of defects from a given commodity before marketing is much less rigorous in developing countries than in developed countries. This, however, is not necessarily bad, because appearance quality is often over-emphasized in developed countries. Postharvest losses vary greatly among commodities and production areas and seasons. In the United States, the losses of fresh fruits and vegetables are estimated to range from 2% to 23%, depending on the commodity, with an overall average of about 12% losses between production and consumption sites (Cappellini and Ceponis, 1984; Harvey, 1978). Kantor et al (1997) estimated the U.S. total retail, foodservice, and consumer food losses in 1995 to be 23% of fruits and 25% of vegetables. Fresh fruits and vegetables accounted for nearly 20% of consumer and foodservice losses, which are due to product deterioration, excess perishable products that are discarded, and plate waste (food not consumed by the purchaser). The latter is often due to consumer dissatisfaction with product quality, especially flavor. Estimates of postharvest losses in developing countries vary greatly from 1 to 50% or even higher (National Academy of Sciences,

Protective effect of BCG among children vaccinated under universal immunization programme.

A case-control study was conducted to estimate the protective effect of BCG vaccination against tuberculosis among children. The children with suspicion of tuberculosis (TB) attending two hospitals in Bangalore city were registered into the study and subjected to detailed clinical examination and investigations. The presence of BCG scar was taken as evidence of vaccination. Modified Stegen-Jones scoring method was adopted for diagnosing TB. The hospital children with score of 7 were considered as TB cases. Children residing in the neighbourhood of cases were similarly investigated and those scoring 4 were labeled as controls. A total of 118 age-sex matched case-control pairs were identified and final analysis was confined to 113 cases and 109 controls after excluding children with doubtful BCG scar. A low protective effect of BCG vaccination at 31% (not significant, statistically) was observed against TB - all forms combined, among children vaccinated as under Universal Immunization Programme. Though the protective efficacy against extra-pulmonary TB was observed to be higher than for pulmonary TB, it was also not significant, statistically. It will be appropriate to conduct further studies on protection rendered by BCG vaccination against tuberculous meningitis and other severe forms of TB. Besides, the quality of vaccination programme including cold chain maintenance also needs to be evaluated.

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.

Priming of measles virus-specific humoral- and cellular-immune responses in macaques by DNA vaccination

Although the currently used live attenuated measles vaccines are safe and effective, they are dependent on cold chain maintenance and are often ineffective in young infants due to interference by maternal antibody. Therefore, besides vector-based vaccines, different new generation non-replicating candidate measles vaccines are being considered, including nucleic acid vaccines. We have vaccinated cynomolgus macaques transdermally with DNA plasmids encoding measles virus (MV) proteins. Following two vaccinations, low serum antibody responses were detected. Wild-type measles virus challenge 1 year after vaccination showed reduced viraemia in some animals. However, accelerated humoral- and cellular-immune responses were observed in all vaccinated macaques, demonstrating successful priming by the DNA vaccines.

Rapid assessment of the quality of services in Rubella immunization provide d through the primary health care service network in the Polonnaruwa district

Objective: To assess the quality of services in munization provided through Primary Health Care clinics at the divisional level using the Lot Quality Assurance Sampling method. Methodology: A non-participant observation was carried out at 20 randomly selected clinics using Lot Quality Assurance Sampling (LQAS) method with a threshold level of a triage system of 80 and 50% The-defective elements (clinics) needed to reject the lot and make improvements was six. Taking into account that not only rubella immunization is provided in a clinic, ten deliveries of rubella immunization in a clinic were studied with a triage system of95 %, 75% (provider risk 1%, Consumer risk 23%), These repetitive activities were judged by LQAS10:3 binary rules. The study instrument was a pre-tested, structured observational checklist that comprised essential activities of vaccination referred to as sub-systems. Results: In the subsystem “sterility”, the hand washing procedure proved to be defective. The maintenance of sterilization chart was found to be poor. Cold chain maintenance was extremely good and none of the related activities was found to be defective. The screening of eligible clients was poor. A tegister of eligible women for rubella immunization was not maintained in any of clinics supervised. The register of immunization was completed after vaccination. In none of clinics were immunized clients totalled and categorized according to age groups at the end of sessions leading to inability to detect any unrecorded vaccinated client by comparing the number of vaccinations with the dosages of vaccines used and to calculate the vaccine wastage. Conclusion: Apart from the defective activities already mentioned, overall quality of services was satisfactory in majority of essential activities Recommendations: It is essential to carry out regular supervisions to detect and modify substandard items by supervisory staff. Steps should be taken to improve documentation during and at the end of the clinic session.

Variation in protection by BCG: implications of and for heterologous immunity.

Abstract Besides being the world's most widely used vaccine, and being directed against the world's leading cause of infectious disease mortality, BCG is the most controversial vaccine in current use. 1,2 Estimates of protection imparted by BCG against pulmonary tuberculosis vary from nil to 80%. This variability has been attributed to strain variation in BCG preparations, to genetic or nutritional differences between populations, and to environmental influences such as sunlight exposure, poor cold-chain maintenance, or exposure to environmental mycobacterial infections. Evidence accumulated to date indicates that regional differences in environmental mycobacteria are responsible for much of the variation observed between populations in the efficacy of BCG against pulmonary tuberculosis. This paper reviews the evidence, and notes its broader implications for the epidemiology and control of mycobacterial diseases as well as for other infections and vaccines.

Stability of oral polio vaccine at different temperatures

The stability of five batches of oral polio vaccine stored at −20, 4–8, 22 and 36°C for 7, 14 and 21 days was studied. The virus titrations were performed by the standard macro-method. There was little loss in virus titre when samples were kept at −20 and 4–8°C for 21 days, whereas the samples exposed to 36°C for 21 days showed almost complete loss in virus titre. The average loss in virus titre in a year (log TCID 50) was 0.47 at −20°C and 0.65 at 4–8°C when various samples were stored at these temperatures. At 22°C the average loss in virus titre after 21 days was about 1.50. The samples subjected to ten cycles of freezing and thawing did not show any loss in virus titre. Likewise there was not much loss in virus titre in three samples stored at 4–8°C for a year. Oral polio vaccine stabilized with magnesium chloride is quite a stable vaccine and maintenance of a proper cold chain is recommended for the delivery of a potent vaccine in countries with high ambient temperature.

Paralytic poliomyelitis in vaccinated children

Although the oral poliovaccine has been effective in the control of poliomyelitis, there are many observations of its failure. To ascertain clinical picture of the disease in vaccinated children and probable causative factors, this study was undertaken. Out of 125 children with Ac. poliomyelitis presented over a period of two years, 16 had received three or more doses of Trivalent-oral poliovaccine. Parents of these children were interviewed to find out possible cause of vaccine failure. All 16 children were below five years, male-female ratio was 9∶7. Twelve received three doses of polio vaccine and four had more doses. Intervals between the last dose of vaccine received and the onset of the disease in all were less than two years. Two had less than one week. Muscle powers in all children at the time of admission were in the range of grade 0/6 to grade 3/6. Poor maintenance of cold chain is probably the only identifiable cause of vaccine failure in 11 children. DPT inoculation along with poliovaccine might be the precipitating factor for paralysis in two children. To overcome these problems there is an urgent need of community involvement in health programmes, reorientation of health workers, a close supervision and steps to improve cold chain. The possibility of using killed poliovaccine should also be explored.