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Biomedical subjects

W A Orenstein

Publications and source records attributed to W A Orenstein.

At least 19 recordsLinked to original sources
PubMed1998

Addressing the challenges to immunization practice with an economic algorithm for vaccine selection.

The biotechnology revolution is producing a growing bounty of new vaccines which pose difficult choices in selecting among many products. Some major public and private purchasers of vaccine may offer individual physicians and clinics their choice in assembling vaccine inventories. Others might purchase only a limited stock of products that would satisfactorily immunize a typical child. In either case, current vaccine selection decisions are based principally on purchase price alone without systematic consideration of other factors of fiscal consequence. As a potential tool for decision making, we developed an economic algorithm for vaccine selection that would minimize the overall costs of disease control through immunization by considering: (1) purchase price, (2) number of doses needed, (3) preparation time, (4) route of administration, (5) cold storage needs, (6) shelf life, (7) earliest age of full immunity, (8) adverse events frequency, and (9) efficacy of protection. To demonstrate the algorithm, variables (1) to (4) above were incorporated into a pilot binary-integer linear programming model that satisfied the recommended immunization schedule for diphtheria, tetanus, pertussis, Haemophilus influenzae b, and hepatitis B, using eleven vaccines (DTaP, DTaP-Hib, Hib, HepB and Hib-HepB) from four manufacturers. Five (or six) opportunities to vaccinate were modeled at (1), 2, 4, 6, 12-18, and 60 months of life, assuming US$40 per clinic visit, $15 per injection, and $0.50 per minute of nurse preparation time. Vaccine costs were varied using actual March and September 1997 US Federal vaccine prices, as well as estimates for unpriced new vaccines. Over 16,000 distinct vaccine stocking lists by vaccine type and brand were possible. Including a 1-month visit, the lowest-cost 'solution' of the algorithm was $529.41 per child in the March cost-assumption case, and $490.32 in the September one (both included four doses of DTaP-Hib, three HepB, and one DTaP). Without a 1-month visit, the lowest-cost solution in the March case cost $486.67 (four DTaP, two Hib-HepB, one DTaP-Hib, and one HepB), while the September case cost $450.32 (four DTaP-Hib, three HepB, and one DTaP). Ensuring at least one product was selected from each of the four manufacturers increased costs about $13.00, and the needed injections rose from eight to nine. The most economical selection of vaccines to use cannot be intuitively predicted, as permutations are large and solutions are sensitive to minor changes in costs and constraints. A transparent, objective selection method that weighs the economic value of distinguishing features among competing vaccines might offer the 'best value' to vaccine purchasers, while also creating strong market incentives for continuing innovation and competition in the vaccine industry.

Adolescent↗
PubMed1996

Rotavirus vaccines--from licensure to disease reduction.

Rotavirus infection produces a serious health burden in the United States, causing an estimated > 100,000 hospitalizations and > 100 deaths annually. This health burden is comparable to that for measles, pertussis, mumps, and varicella before vaccines for these diseases were routinely given to children. Rotavirus vaccines have the potential to significantly reduce a serious public health problem in the United States. However, while development and licensure of vaccines is a major breakthrough, it represents only the first step in disease prevention. Vaccines must be recommended by major immunization advisory committees, financed in both the public and private sectors, and successfully integrated into the existing vaccination schedule. Vaccines must reach all targeted children, and monitoring systems must be established or adapted to better determine vaccine safety and disease impact. Reevaluation of disease prevention strategies must be ongoing and fueled by new information on safety and disease reduction.

Child, Preschool↗
PubMed1995

The effect of disease prior to an outbreak on estimates of vaccine efficacy following the outbreak.

A common source of bias in evaluating vaccine efficacy following a disease outbreak is the presence of persons who had the disease prior to the outbreak. This paper examines the effects of including and excluding pre-outbreak disease cases from the calculation of vaccine efficacy based on the cumulative incidence at the end of an outbreak. Using a five-stage model, the effects of the following factors on the bias of vaccine efficacy estimates are examined: the true protective efficacy of the vaccine, the prevaccination infection rate, differences in vaccine uptake among the previously diseased and nondiseased, differences in pre-outbreak exposure to infection between vaccinees and nonvaccinees, and differences in exposure during the outbreak between vaccinees and nonvaccinees. Numerical calculations of the bias are performed for a hypothetical outbreak of measles in a developing country. Exclusion of pre-outbreak disease cases requires accurate data on disease rates prior to the outbreak, and such data are often unreliable or nonexistent. Inclusion of pre-outbreak cases contributes to the bias of the estimated vaccine efficacy, especially when there is a high prevaccination infection rate and vaccine uptake among the previously diseased is considerably lower than that among the nondiseased. In most practical cases, however, this bias is not very large.

Disease Outbreaks↗
PubMed1994

Quest for life-long protection by vaccination.

Life-long protection from disease through immunization can be accomplished through individual or community protection. Individual protection is the goal for vaccination against diseases that have inanimate or animal reservoirs or that pose risks for certain populations. Community protection is the goal for vaccination against diseases that are transmitted only from human to human. Community protection afforded by childhood vaccines has been highly successful against measles, rubella, mumps, and polio. However, outbreaks of measles, rubella, and mumps continue to occur, primarily because of inadequate immunization of children under age 2. Simplification of vaccination regimens, provision of incentives to care providers and parents, and increased access to care should improve vaccination rates in the United States. Better protection requires better use of available vaccines. Eradication of disease through vaccination is the ultimate goal of community protection. Elimination of the infectious agent is the most effective means of achieving life-long protection. The World Health Organization's (WHO) smallpox eradication campaign eliminated a serious disease as well as the need for a vaccine with frequent and severe adverse reactions. The discontinuation of smallpox vaccination in the United States has produced a savings of over $3 billion. Polio has been targeted by WHO for eradication by the year 2000. The eradication of polio and the elimination of the need for polio vaccination in the United States should result in a savings of $110 million per year in vaccine costs alone. Strong United States support is crucial for WHO to reach its goal. Any of the vaccine-preventable childhood virus diseases could be eradicated with sufficient national and international will. Measles and hepatitis B should be high priorities. The ultimate goal of vaccination is life-long protection of all individuals. Any disease of sufficient public health importance to warrant routine vaccination is of sufficient importance to warrant eradication wherever judged to be possible.

Bacterial Infections↗
PubMed1992

Measles surveillance--United States, 1991.

A total of 9,643 measles cases was reported from the United States in 1991, a 65.3% decrease from the 27,786 cases reported in 1990. The overall incidence of measles was 3.9 cases per 100,000 population. The highest age-specific incidence was among children < 12 months of age (46.9/100,000) and 1-4 years of age (19.6/100,000). Incidence rates among American Indians, Hispanic, and black children < 5 years of age were 19, 6, and 4 times that for non-Hispanic white children, respectively. More than 61% of all cases were reported from seven large outbreaks, which involved predominantly unvaccinated preschool-age children in large urban areas. Although reported measles cases decreased in 1991 compared with 1989-1990, only a sustained effort to provide age-appropriate vaccination will prevent another resurgence of measles.

Adolescent↗
PubMed1992

Monitoring progress toward US preschool immunization goals.

The United States has achieved over 97% immunization of children by school age and has reduced the incidence of vaccine-preventable diseases by more than 90% since the prevaccination era. However, children often do not receive immunizations at the recommended age, and in densely populated urban areas this delay in immunization has led to epidemics of measles. Correctable deficiencies of the immunization delivery system have been identified in these areas. To respond to needs, the public health infrastructure must be strengthened, and active participation from the private sector must be obtained, both in delivery of immunizations and in assessment of performance. Appropriate action must be stimulated by the provision of timely information on immunization coverage and on indicators of program performance at the local level.

Child, Preschool↗
PubMed1992

When, where, and how do immunizations fail?

There are two main reasons for failure of immunizations: (1) failure of the vaccine delivery system to provide potent vaccines properly to persons in need; and (2) failure of the immune response, whether due to inadequacies of the vaccine or factors inherent in the host. The first category is by far the most important worldwide. The major factor contributing to failure of the delivery system is failure to vaccinate; in the developing world this is commonly a result of inadequacy of the vaccine supply. Other important factors include barriers to immunizations, improper use of vaccines, vaccine ineffectiveness at the time of use, and factors relating to client attitudes and knowledge. Failure of the immune response may be either primary or secondary (loss of protection after initial effectiveness). The shortcomings of existing vaccines must not deter us from taking maximal advantage of their benefits.

Humans↗
PubMed1992

Epidemiology of poliomyelitis in the United States one decade after the last reported case of indigenous wild virus-associated disease.

Poliomyelitis caused by wild poliovirus has been virtually nonexistent in the United States since 1980, and vaccine-associated paralytic poliomyelitis (VAPP) has emerged as the predominant form of the disease. We reviewed national surveillance data on poliomyelitis for 1960-1989 to assess the changing risks of wild-virus, vaccine-associated, and imported paralytic disease; we also sought to characterize the epidemiology of poliomyelitis for the period 1980-1989. The risk of VAPP has remained exceedingly low but stable since the mid-1960s, with approximately 1 case occurring per 2.5 million doses of oral poliovirus vaccine (OPV) distributed during 1980-1989. Since 1980 no indigenous cases of wild-virus disease, 80 cases of VAPP, and five cases of imported disease have been reported in the United States. Three distinct groups are at risk of vaccine-associated disease: recipients of OPV (usually infants receiving their first dose), persons in contact with OPV recipients (mostly unvaccinated or inadequately vaccinated adults), and immunologically abnormal individuals. Overall, 93% of cases in OPV recipients and 76% of vaccine-associated cases have been related to administration of the first or second dose of OPV. Our findings suggest that adoption of a sequential vaccination schedule (inactivated poliovirus vaccine followed by OPV) would be effective in decreasing the risk of VAPP while retaining the proven public health benefits of OPV.

Humans↗