Vaccination Related Factors Research Articles

Vaccine epidemiology, evaluation, and constraints of vaccine effectiveness -A review

Vaccines are all biological substances produced from living things, administered to trigger the host's body defense system to develop immunity against a specific pathogen from which they are produced. They are produced either from the whole organism or parts of it. There are several types of vaccines like live virulent, live attenuated, inactivated (killed), subunit, toxoid, sero-vaccine, and autogenous vaccine. Vaccines work by stimulating either humoral or cell-mediated immunity or both to differentiate. Even though vaccination is the powerful and cost-effective weapon of disease prevention and control of infectious and non infectious diseases, there are factors those, hinder its effectiveness (constraints of vaccine effectiveness). These factors are technical constraints, pathogen-related constraints, vaccine-related factors, host-related and environmental and management-related constraints. While planning a vaccination regimen, it is important to test the potency of the vaccine, whether it much with circulating serotype, availability of cold chain, skilled manpower, the status of the target group and weather condition. Vaccine epidemiology, the study of vaccine interactions and impacts on the epidemiology of vaccine-preventable diseases also has an impact on vaccine effectiveness. it includes basic reproductive number, the force of infection, herd immunity, and epidemiologic shift. Some review papers mostly deal with constraints of specific vaccines and species of animals and with a specific constraint of the vaccine. However, the papers which review all common constraints of vaccine are limited. Therefore, this review paper is to address the most common constraints on the effectiveness of vaccines in all animal species and to highlight on evaluation of vaccine effectiveness and epidemiology.

Impact of COVID-19 vaccine-associated side effects on health care worker absenteeism and future booster vaccination

BackgroundShort-term side effects related to mRNA vaccines against SARS-CoV-2 are frequent and bothersome, with the potential to disrupt work duties and impact future vaccine decision-making. ObjectiveTo identify factors more likely to lead to vaccine-associated work disruption, employee absenteeism, and future vaccine reluctance among healthcare workers (HCWs). HypothesisSide effects related to COVID vaccination: 1- frequently disrupt HCW duties, 2- result in a significant proportion of HCW absenteeism, 3- contribute to uncertainty about future booster vaccination, 4- vary based on certain demographic, socioeconomic, occupational, and vaccine-related factors. MethodsUsing an anonymous, voluntary electronic survey, we obtained responses from a large, heterogeneous sample of COVID-19-vaccinated HCWs in two healthcare systems in Southern California. Descriptive statistics and regression models were utilized to evaluate the research questions. ResultsAmong 2,103 vaccinated HCWs, 579 (27.5%) reported that vaccine-related symptoms disrupted their professional responsibilities, and 380 (18.1%) missed work as a result. Independent predictors for absenteeism included experiencing generalized and work-disruptive symptoms, and receiving the Moderna vaccine [OR = 1.77 (95% CI = 1.33 – 2.36), p < 0.001]. Physicians were less likely to miss work due to side effects (6.7% vs 21.2% for all other HCWs, p < 0.001). Independent predictors of reluctance toward future booster vaccination included lower education level, younger age, having received the Moderna vaccine, and missing work due to vaccine-related symptoms. ConclusionSymptoms related to mRNA vaccinations against SARS-CoV-2 may frequently disrupt work duties, lead to absenteeism, and impact future vaccine decision-making. This may be more common in Moderna recipients and less likely among physicians. Accordingly, health employers should schedule future booster vaccination cycles to minimize loss of work productivity.

COVID-19-Related Vaccine Hesitancy among Community Hospitals' Healthcare Workers in Singapore.

COVID-19 has culminated in widespread infections and increased deaths over the last 3 years. In addition, it has also resulted in collateral economic and geopolitical tensions. Vaccination remains one of the cornerstones in the fight against COVID-19. Vaccine hesitancy must be critically evaluated in individual countries to promote vaccine uptake. We describe a survey conducted in three Singapore community hospitals looking at healthcare workers’ vaccine hesitancy and the barriers for its uptake. The online anonymous survey was conducted from March to July 2021 on all staff across three community hospital sites in SingHealth Singapore. The questionnaire was developed following a scoping review and was pilot tested and finalized into a 58-item instrument capturing data on demographics, contextual features, knowledge, attitudes, perceptions, and other vaccine-related factors in the vaccine hesitancy matrix. Logistic regression analysis was employed for all co-variates that are significant in univariate analysis. The response rate was 23.9%, and the vaccine hesitancy prevalence was 48.5% in the initial phase of the pandemic. On logistic regression analysis, only being female, a younger age, not having had a loved one or friend infected with COVID-19 and obtaining information from newspapers were associated with vaccine hesitancy in healthcare workers in Singapore community hospitals.

Attitude toward a mandatory COVID-19 vaccination policy and its determinants: Evidence from serial cross-sectional surveys conducted throughout the pandemic in Germany

BackgroundMandating vaccination against COVID-19 is often discussed as a means to counter low vaccine uptake. Beyond the potential legal, ethical, and psychological concerns, a successful implementation also needs to consider citizens’ support for such a policy. Public attitudes toward vaccination mandates and their determinants might differ over time and, hence, should be monitored. MethodsBetween April 2020 and April 2021, we investigated public support for mandatory vaccination policies in Germany and examined individual correlates, such as vaccination intentions, confidence in vaccine safety, and perceived collective responsibility, using a series of cross-sectional, quota-representative surveys (overall N = 27,509). ResultsSupport for a vaccination mandate declined before the approval of the first vaccine against COVID-19 in December 2020 and increased afterwards. However, at the end of April 2021, only half of respondents were in favor of mandatory regulations. In general, mandates were endorsed by those who considered the vaccines to be safe, anticipated practical barriers, and felt responsible for the collective. On the contrary, perceiving vaccination as unnecessary and weighing the benefits and risks of vaccination was related to lower support. Older individuals and males more often endorsed vaccination mandates than did younger participants and females. Interestingly, there was a gap between vaccination intentions and support for mandates, showing that the attitude toward mandatory vaccination was not only determined by vaccination-related factors such as vaccine safety or prosocial considerations. ConclusionsBecause of low public support, mandatory vaccination against COVID-19 should be considered a measure of last resort in Germany. However, if removing barriers to vaccination and educational campaigns about vaccine safety and the societal benefits of high vaccination uptake are not sufficient for increasing vaccination uptake to the required levels, mandates could be introduced. In this case, measures to ensure and increase acceptance and adherence should be taken.

Safety of SARS-CoV-2 vaccines in patients with chronic myeloid leukemia: a multicenter survey in China.

Safety of SARS-CoV-2 vaccines in patients with chronic myeloid leukemia: a multicenter survey in China.

Canadian parents’ perceptions of COVID-19 vaccination and intention to vaccinate their children: Results from a cross-sectional national survey

BackgroundVaccinating children (≤17 years old) is important for controlling the COVID-19 pandemic. As parents are primary decision makers for their children, we aimed to assess parents’ perceptions and intentions regarding COVID-19 vaccination for their children, including for some underserved populations (e.g., newcomers, Indigenous peoples, and visible minority groups). MethodsWe conducted a cross-sectional national survey of Canadian parents in December 2020, just as COVID-19 vaccines were approved for adults, to assess intention to vaccinate their children (aged 0–17 years) against COVID-19, perceptions of COVID-19 disease and vaccines, previous uptake of influenza and routine vaccines, and sociodemographic characteristics. Binomial logistic regression was used to assess the association between parents' lack of COVID-19 vaccination intention for their children and various independent variables. ResultsSixty-three percent of parents (1074/1702) intended to vaccinate their children against COVID-19. Those employed part-time (compared to full-time) had lower intention to vaccinate their children (aOR = 1.73, 95% CI: 1.06–2.84), while those who spoke languages other than English, French, or Indigenous languages were less likely to have low intention (aOR = 0.55, 95% CI: 0.32–0.92). Low vaccination intention was also associated with children not receiving influenza vaccine pre-pandemic (aOR = 1.51, 95% CI: 1.04–2.21), parents having low intention to vaccinate themselves against COVID-19 (aOR = 9.22, 95% CI: 6.43–13.34), believing COVID-19 vaccination is unnecessary (aOR = 2.59, 95% CI: 1.72–3.91) or unsafe (aOR = 4.21, 95% CI: 2.96–5.99), and opposing COVID-19 vaccine use in children without prior testing (aOR = 3.09, 95% CI: 1.87–5.24). InterpretationParents’ COVID-19 vaccination intentions for their children are better predicted by previous decisions regarding influenza vaccination than routine childhood vaccines, and other perceptions of COVID-19 vaccine-related factors. Public communication should highlight the safety and necessity of COVID-19 vaccination in children to support a return to normal activities. Further research should assess actual COVID-19 vaccination uptake in children, particularly for underserved populations.

Barriers and facilitators to influenza and pneumococcal vaccine hesitancy in rheumatoid arthritis: a qualitative study

Immunization is an essential component of rheumatoid arthritis (RA) care. Nevertheless, vaccine coverage in RA is suboptimal. Contextual, individual, and vaccine-related factors influence vaccine acceptance. However, barriers and facilitators of vaccination in RA are not well defined. The aim of this study was to assess perspectives of RA patients and health care professionals (HCPs) involved in RA care of barriers and facilitators regarding influenza and pneumococcal vaccines. Eight focus groups (4 with RA patients and 4 with HCPs), and eight semi-structured open-ended individual interviews with vaccine hesitant RA patients were conducted. Data were audio-recorded, transcribed verbatim, and imported to the MAXQDA software. Analysis using the framework of vaccine hesitancy proposed by the Strategic Advisory Group of Experts (SAGE) on Immunization was conducted. RA patients and HCPs reported common and specific barriers and facilitators to influenza vaccination that included contextual, individual and/or group, and vaccine and/or vaccination specific factors. A key contextual influence on vaccination was patients' perception of the media, pharmaceutical industry, authorities, scientists, and the medical community at large. Among the individual-related influences, experiences with vaccination, knowledge/awareness, and beliefs about health and disease prevention were considered to impact vaccine-acceptance. Vaccine-related factors including concerns of vaccine side effects such as RA flares, safety of new formulations, mechanism of action, access to vaccines and costs associated with vaccination were identified as actionable barriers. Acknowledging RA patients' perceived barriers to influenza and pneumococcal vaccination and implementing specific strategies to address them might increase vaccination coverage in this population.

POS1268 COVID-19 VACCINE HESITANCY AMONG RHEUMATOLOGY PATIENTS RECEIVING INFLUENZA VACCINE

Background:Adults with rheumatic diseases are a COVID-19 vulnerable population with potential increased risk for severe infection. COVID-19 vaccines are a key strategy to ending the pandemic. Unfortunately, fears about vaccines, some of which are propagated by misinformation, are common and may prevent or inappropriately delay vaccination. Refusal or uncertainty to get a vaccine despite its availability is known as vaccine hesitancy.Objectives:This study aims at defining causes of COVID-19 vaccine hesitancy among rheumatology patients.Methods:Between November and December 2020, a cross-sectional survey was completed by rheumatology patients presenting to a large Canadian tertiary-care center for influenza immunization. COVID-19 risk factors, previous COVID-19 infection, the likelihood of getting a future COVID-19 vaccine (scale 0-10), and contextual, individual, and vaccine-specific potential determinants of vaccine hesitancy were assessed. Patients were classified into 5 groups based on how likely they were to get a future COVID-19 vaccine (0= not likely at all; 2.5= unlikely; 5= intermediate; 7.5= likely; 10= highly likely). A machine learning approach (XgBoost) was used to fit univariate models for a multi-class correlation.Results:157 rheumatology patients completed the survey. Most were females (n=112, 71%) with a mean age of 54.6 (standard deviation 17.9). The majority (73%) had tertiary-education, and 46% were employed at the time of the survey. The most common rheumatology diagnoses were rheumatoid arthritis (n=90, 58%), systemic lupus erythematosus/vasculitis (n=41, 26%) and spondyloarthropathies (n=39, 25%). Most patients were on immunosuppressors (n=93, 59%). Only half (n=85, 54%) were highly likely to accept a future COVID vaccine, 17% (n=26) likely, 19% (n=30) intermediate, 6% (n=10) unlikely, and 4% (n=6) not likely at all. One hundred thirty-five patients (86%) previously received the flu vaccine, whereas 6% (n=10) previously rejected it. Only three patients were previously diagnosed with COVID-19 (2%) one of whom was hospitalized. Eighty-seven patients (56%) considered that the COVID-19 vaccine should be mandatory, and 101 (65%) that they should receive it. Most respondents were somewhat concerned about receiving a future COVID-19 vaccine (n=116, 76%) despite that 65% believed that vaccines benefits outweighed their risks. Almost all, (n=145, 96%) believed that governmental decisions about vaccines are in the best interest of the population, while less than half (n=70, 45%) were confident that pharmaceutical companies would provide safe and effective vaccines. One hundred participants (65%) denied feeling social pressure to get the vaccine, and 55% (n=81) were willing to pay for the vaccine. Feeling social pressure about getting a COVID-19 vaccine, having severe concerns about receiving a future COVID-19 vaccine, distrust in pharmaceutical companies, lower education, and doubts of whether vaccines benefits outweigh their risks, were negatively associated with COVID vaccine acceptance.Conclusion:Forty six percent of rheumatology patients being immunized against influenza showed at least some hesitancy towards COVID-19 vaccination. Multiple contextual, individual, and vaccine-related factors may contribute. Targeted educational strategies, including producing and communicating data on vaccine safety, may help promote vaccine uptake in this potentially vulnerable population.Disclosure of Interests:None declared

Mapping Host-Related Correlates of Influenza Vaccine-Induced Immune Response: An Umbrella Review of the Available Systematic Reviews and Meta-Analyses.

Seasonal influenza is the leading infectious disease in terms of its health and socioeconomic impact. Annual immunization is the most efficient way to reduce this burden. Several correlates of influenza vaccine-induced protection are commonly used, owing to their ready availability and cheapness. Influenza vaccine-induced immunogenicity is a function of host-, virus- and vaccine-related factors. Host-related factors constitute the most heterogeneous group. The objective of this study was to analyze the available systematic evidence on the host factors able to modify influenza vaccine-induced immunogenicity. An umbrella review approach was undertaken. A total of 28 systematic reviews/meta-analyses were analyzed—these covered the following domains: intravenous drug use, psychological stress, acute and chronic physical exercise, genetic polymorphisms, use of pre-/pro-/symbiotics, previous Bacillus Calmette–Guérin vaccination, diabetes mellitus, vitamin D supplementation/deficiency, latent cytomegalovirus infection and various forms of immunosuppression. In order to present effect sizes on the same scale, all possible meta-analyses were re-performed and cumulative evidence synthesis ranking was carried out. The meta-analysis was conducted separately on each health condition category and virus (sub)type. A total of 97 pooled estimates were used in order to construct an evidence-based stakeholder-friendly map. The principal public health implications are discussed.

Enhancement of Antitumor Vaccination by Targeting Dendritic Cell-Related IL-10.

Understanding mechanisms associated to dendritic cell (DC) functions has allowed developing new antitumor therapeutic vaccination strategies. However, these vaccines have demonstrated limited clinical results. Although the low immunogenicity of tumor antigens used and the presence of tumor-associated suppressive factors may in part account for these results, intrinsic vaccine-related factors may also be involved. Vaccines modulate DC functions by inducing activating and inhibitory signals that determine ensuing T cell responses. In this mini review, we focus on IL-10, inhibitory cytokine induced in DC upon vaccination, which defines a suppressive cell subset, discussing its implications as a potential target in combined vaccination immunotherapies.

Are vaccine strain, type or administration protocol risk factors for canine parvovirus vaccine failure?

Canine parvovirus (CPV) is a highly contagious and worldwide cause of serious and often fatal disease in dogs, despite the widespread availability of vaccines. Which vaccine-related factors are associated with vaccination failure is largely unknown, and there are no reports from Australia. In this study – the first national population-level CPV study of its kind ever conducted – we analysed data on 594 cases of apparent CPV vaccination failure reported from an Australian national surveillance system to determine whether vaccine strain, type or administration protocol are risk factors for vaccination failures. The strain of CPV used in vaccine manufacture was not significantly associated with vaccination failure in clinical practice. The vaccine type (killed versus attenuated vaccine) for puppies diagnosed with CPV was associated with a lower mean age at time of vaccination (P=0.0495). The age at administration of the last CPV vaccination a puppy received prior to presenting with disease was a significant (P=0.0334) risk factor for vaccination failure, irrespective of whether the vaccine was marketed for a 10-week or 12-week or greater vaccination finish protocol. There was also a strong negative correlation between age at last vaccination prior to disease and vaccination failure (P<0.0001): the later a puppy received this last vaccination, the lower the risk of vaccination failure. This supports the hypothesis that the use of final vaccination in puppies at less than 16 weeks of age predisposes to vaccination failure and warrants a final age for vaccination recommendation to be at least 16 weeks for all canine parvovirus vaccines, especially in outbreak situations. The large number of cases identified in this study confirms that CPV vaccination failure is occurring in Australia. Veterinarians should consider CPV as a differential diagnosis in cases with appropriate clinical presentation, regardless of the reported vaccination status of the dog.

Coverage Rate and Factors Associated with Vaccination in Adult Recommended Pneumococcal Vaccine

Objectives: The purpose of this study was to measure the rate of pneumococcal vaccination and vaccination-related factors and to identify the predictors of vaccine uptake behavior among the adults recommended for the immunization. Methods: Cross-sectional survey was performed with questionnaires provided to 205 adults who recommended for the immunization among inpatients and outpatients admitted to a single metropolitan hospital in the February and March of 2015. Collected data were analyzed by descriptive statistics, χ2-test, t-test, and multiple logistic regression analyses using IBM SPSS WIN 22.0 program. Results: Vaccination rate of the participants was 23.9%. Their knowledge for the vaccination and pneumonia-preventive behavior were at intermediate levels, scoring 5.85/10 and 6.47/10 points, respectively. Their health beliefs that include susceptibility, seriousness, benefits, barriers and cues to action scored 69.18/100. Vaccinees scored significantly higher than the non-vaccinee controls in the knowledge for vaccination and also in the susceptibility and severity of health belief. Vaccine receipt rate differed significantly in univariate analysis by general characteristics such as age, education, marital status but not by gender and comorbidity. Further analyses of multiple logistic regression indicated that the vaccine receipt rate appeared to increase with age, experience of pneumonia and perceived susceptibility. Conclusions: The pneumococcal vaccination rate was generally low. To increase the rate, it is desirable to develop an organized program to educate vaccine recommended adults and enhance their perception of the risk of pneumococcal infection and the benefit of vaccination. Key words: Pneumococcal vaccine for adults, Vaccine uptake rate, Vaccination related factor

Social and psychological factors underlying adult vaccination behavior: lessons from seasonal influenza vaccination in the US and the UK

This article reviews the evidence base on the social and psychological factors that facilitate or hinder vaccination among adults. The authors categorized these factors into eight themes: social influence, disease-related factors, vaccine-related factors, habit, general attitudes toward health and vaccines, awareness and knowledge, practical barriers and motivators and altruism. Although there were many commonalities between both settings, the authors also indentifiedimportant differences. A better understanding of social and psychological aspects of vaccination across contexts and vaccines remains a priority.

Mothers' HPV-related Knowledge in an Area

Purpose: This study was aimed to examine mothers’knowledge about human papillomavirus (HPV)vaccination to prevent cervical cancer in Korea. Methods: From September 20 to October 10 2011, 101 mothers who have adolescent girls were surveyed with questionnaires about their general characteristics, the knowledge of HPV vaccine, inoculation rate and vaccination-related factors of their daughters. Results: The percentage of correct answers for HPV vaccine knowledge was 24.2% and the HPV vaccination rate was only 5.9%. HPV vaccine knowledge score of the vaccination group was significantly higher than that of the non-vaccinated group. Mothers said that the reasons why they didn’t vaccinate their daughters against the HPV was the financial burden, the lack of HPV knowledge, and worries about possible side effects. The participants addressed that they understood the appropriate age for vaccination was sixteen. Conclusion: We recommend that more educational and promotional efforts need to be given for mothers in order to improve their knowledge of HPV vaccination and to increase the performance rates of HPV immunization against cervical cancer for their daughters.

Cost-effectiveness of vaccination against cervical cancer: A multi-regional analysis assessing the impact of vaccine characteristics and alternative vaccination scenarios

Mathematical models provide valuable insights into the public health and economic impact of cervical cancer vaccination programmes. An in-depth economic analysis should explore the effects of different vaccine-related factors and vaccination scenarios (independent of screening practices) on health benefits and costs. In this analysis, a Markov cohort model was used to explore the impact of vaccine characteristics (e.g. cross-type protection and waning of immunity) and different vaccination scenarios (e.g. age at vaccination and multiple cohort strategies) on the cost-effectiveness results of cervical cancer vaccination programmes. The analysis was applied across different regions in the world (Chile, Finland, Ireland, Poland and Taiwan) to describe the influence of location-specific conditions. The results indicate that in all the different settings cervical cancer vaccination becomes more cost-effective with broader and sustained vaccine protection, with vaccination at younger ages, and with the inclusion of several cohorts. When other factors were varied, the cost-effectiveness of vaccination was most negatively impacted by increasing the discount rate applied to costs and health effects.

Influenza vaccination among the elderly Spanish population: trend from 1993 to 2003 and vaccination-related factors*

Influenza is an important public health problem that particularly affects elderly subjects and influenza vaccination is a safe, effective and efficient method for prevention of influenza-related complications in elderly individuals with or without underlying chronic conditions. This study aims to analyze adjusted time trends in the coverage of influenza vaccination among elderly Spanish subjects and to identify which variables were associated with the probability of having been vaccinated in 2003. We undertook a cross-sectional study using data of individuals aged >/=65 years drawn from the 1993, 1995, 1997, 2001, and 2003 Spanish National Health Surveys. The answer to the question 'Did you have a 'flu shot in the latest campaign' was used as the dependent variable, and socio-demographic and health-related characteristics were analyzed as independent variables. Coverage of vaccination for each year was adjusted by the direct method for both age and gender. Multivariate logistic regression was used to estimate the independent effect of variables on the receipt of influenza vaccine. 15 989 records were analyzed. Adjusted influenza coverage increased from 50.1% in 1993 to 63.7% in 2003 (P < 0.001). The variables that were significantly associated with a higher likelihood of being vaccinated were older age, suffering a chronic disease, residence in towns with <10 000 inhabitants, 'worse' self-perceived health and non-smokers. Coverage among the Spanish elderly has increased significantly from 1993 to 2003. Still, there is room for improvement, particularly, among the subjects with 'good' self-perceived health, those with no concomitant medical conditions, and smokers.

Human genetics and responses to influenza vaccination: clinical implications.

Influenza A and B viruses are negative-strand RNA viruses that cause regular outbreaks of respiratory disease and substantially impact on morbidity and mortality. Our primary defense against the influenza virus infection is provided by neutralizing antibodies that inhibit the function of the virus surface coat proteins hemagglutinin and neuraminidase. Production of these antibodies by B lymphocytes requires help from CD4+ T cells. The most commonly used vaccines against the influenza virus comprise purified preparations of hemagglutinin and neuraminidase, and are designed to induce a protective neutralizing antibody response. Because of regular antigenic change in these proteins (drift and shift mutation), the vaccines have to be administered on an annual basis. Current defense strategies center on prophylactic vaccination of those individuals who are considered to be most at risk from the serious complications of infection (principally individuals aged >65 years and those with chronic respiratory, cardiac, or metabolic disease). The clinical effectiveness of influenza virus vaccination is dependent on several vaccine-related factors, including the quantity of hemagglutinin within the vaccine, the number of doses administered, and the route of immunization. In addition, the immunocompetence of the recipient, their previous exposure to influenza virus and influenza virus vaccines, and the closeness of the match between the vaccine and circulating influenza virus strains, all influence the serologic response to vaccination.However, even when these vaccines are administered to young fit adults a proportion of individuals do not mount a significant serologic response to the vaccine. It is not clear whether these nonresponding individuals are genetically pre-programmed to be nonresponders or whether failure to respond to the vaccine is a random event. There is good evidence that nonresponsiveness to hepatitis B vaccine, another purified protein vaccine, is at least partially modulated by an individual's human leucocyte antigen (HLA) alleles. Because CD4+ T cells, which control the neutralizing antibody response to influenza virus, recognize antigens in association with HLA class II molecules, we recently conducted a small study to investigate whether there was any association between HLA class II molecules and nonresponsiveness to influenza virus vaccination. This work revealed that the HLA-DRB1*0701 allele was over represented among persons who fail to mount a neutralizing antibody response. This preliminary finding is important because it potentially identifies a group who may not be protected by current vaccination strategies. Further investigation into the role of HLA polymorphisms and nonresponse to influenza virus vaccination, and vaccination against viruses in general, is clearly required.

Controversies in BCG immunization.

Despite controversies BCG vaccination has stood the test of time. World Health Organization continues to recommend its use in infant immunization programme in countries with heavy endemicity and where threatening HIV epidemic in an emerging problem > 85% efficacy have been established in recent years against hematogenous spread of the disease and > or = 50% efficacy even against pulmonary tuberculosis. Host related factors, agent related factors, vaccine related factors and inadequacy of evaluation tests determine the BCG vaccine efficacy. Identification of complete BCG genome in 1998 has opened new vistas in newer BCG vaccine development. Adoption of a '5C' concept viz. Case detection, Chemotherapy short course, Contact elimination, Chemoprophylaxis and lastly control in BCG vaccine will be a desirable national approach in combating adult and childhood TB.

Estimation of vaccine efficacy from epidemics of acute infectious agents under vaccine-related heterogeneity

A stochastic model is formulated for the study of the protective effects of vaccination in a population that is stratified by vaccine-related factors. The epidemic model is transformed into a counting process, and then martingale-based methods are used to provide estimators of vaccine efficacy and their variances. following an example, various extensions of the model are discussed.

Integration of Hepatitis B Vaccine into the Expanded Program on Immunization: The Saudi Arabian Experience

Hepatitis B virus (HBV) is endemic in the Kingdom of Saudi Arabia. To prevent the chronic carriage of HBV in Saudi children, hepatitis B vaccine was added as the seventh immunogen in the expanded program on immunization (EPI). In the first year, the coverage of the first dose and third dose of HB vaccine was 90% and 73%, respectively. In a survey of 637 children, 603 (95%) were positive for antibody to hepatitis surface antigen (anti-HBs) without concomintant antibody to hepatitis B core antigen (anti-HBc) or hepatitis B surface antigen (HBsAg). A total of 592 (93%) with anti-HBs titer of > 10 IU/L were considered as responders to the vaccine. The majority (60%) of these responders had titers > 100 IU/L. Only one (0.3%) non-responder was positive for anti-HBc alone. Using historical control, the protective efficacy was estimated as 99%. Neither the gender of the recipient, schedule of the vaccination, nor the sourve of vaccine influenced the response to the vaccine. The successful integration of the HB vaccine into the EPI was due to the effectiveness of the EPI and the efficient primary health care system in Saudi Arabia.