A Modeling Procedure of the Broadband Dielectric Spectroscopy for Ionic Liquids.

The dielectric spectroscopy (DS) measurement is an attractive noninvasive method to reveal the intrinsic information of biological materials and cell cultures. However, the presence of a double layer due to electrode polarization within the lower RF and microwave range significantly affects the accurate analysis of dielectric properties of ionic liquids. In this paper, we measure the broadband DS of five saline solutions with a microfluidic coplanar waveguide (CPW) transmission line sensor across the frequency range from 40 kHz to 110 GHz. Derived from a parallel-plate structure that is transformed from the quasi-TEM CPW sensor through a conformal mapping technique, a broadband spectroscopy modeling method is proposed, where a Cole-Cole function or a constant phase element formula is used depending on the ionic concentrations and the measurement window. Validation analysis on the five saline solutions demonstrates the capability of the modeling method in separating relaxation properties of the bulk sample from the double-layer effects.

Global eradication of poliomyelitis: benefit-cost analysis.

A benefit-cost analysis of the Poliomyelitis Eradication Initiative was undertaken to facilitate national and international decision-making with regard to financial support. The base case examined the net costs and benefits during the period 1986-2040; the model assumed differential costs for oral poliovirus vaccine (OPV) and vaccine delivery in industrialized and developing countries, and ignored all benefits aside from reductions in direct costs for treatment and rehabilitation. The model showed that the "break-even" point at which benefits exceeded costs was the year 2007, with a saving of US$ 13 600 million by the year 2040. Sensitivity analyses revealed only small differences in the break-even point and in the dollars saved, when compared with the base case, even with large variations in the target age group for vaccination, the proportion of case-patients seeking medical attention, and the cost of vaccine delivery. The technical feasibility of global eradication is supported by the availability of an easily administered, inexpensive vaccine (OPV), the epidemiological characteristics of poliomyelitis, and the successful experience in the Americas with elimination of wild poliovirus infection. This model demonstrates that the Poliomyelitis Eradication Initiative is economically justified.

Vaccine-preventable disease and immunization in the developing world.

Vaccines have given health care providers control over a substantial portion of the morbidity and mortality in the developing world. Global efforts have immunized two-thirds of the world's children with DTP and polio vaccines; 72% have received BCG and 59% measles vaccine; but only 29% of pregnant women have received two doses of tetanus toxoid. In addition, vaccines against yellow fever, Japanese encephalitis, hepatitis B, rubella, and mumps and meningococcal polysaccharide vaccine are being used in specific regions of the world. New vaccine candidates will enhance the vaccine armamentarium over the next decade to include the causes of pneumonia, diarrhea, and meningitis: Haemophilus influenzae type b, pneumococcal and meningococcal protein conjugate vaccines, typhoid and rotavirus vaccine. Genetically engineered vaccine vehicles, genetic reassortants, and genetic deletions are being investigated as new vaccine candidates.

Vaccine-associated paralytic poliomyelitis. United States: 1973 through 1984.

From 1973 through 1984, there were 138 cases of paralytic poliomyelitis reported in the United States; 105 (76%) were vaccine associated. Of the 105 vaccine-associated cases, 35 occurred in recipients of oral polio vaccine (OPV), 50 in contacts to OPV recipients, 14 in immune deficient individuals, and six in individuals who had no history of receiving OPV or contact with recent OPV recipients. Thirty-three (94%) of the recipient cases, 41 (82%) of the contact cases, and five (36%) of the immune deficient cases were associated with the first dose of OPV. The overall frequency of vaccine-associated poliomyelitis was one case per 2.6 million doses distributed. However, the relative frequency of paralysis associated with the first dose in the OPV series was one case per 520,000 doses vs one case per 12.3 million subsequent doses. Vaccine-associated paralytic poliomyelitis is rare and the risks of OPV are small. The greatest likelihood of paralysis occurs in association with the first dose of OPV and that likelihood is reduced in subsequent doses more for recipients than for their contacts.

Prevalence of rubella antibodies in Massachusetts schoolchildren.

In 1982, 1,871 (79%) of 2,368 eligible 6th, 10th and 12th grade students in Massachusetts participated in a statewide serosurvey for rubella antibodies. Sera were screened at the Centers for Disease Control (CDC) by a reference hemagglutination inhibition assay at 1:8, equivalent to approximately 15 International Units (IU)/ml. Sera negative by the CDC hemagglutination inhibition assay were retested using an enzyme immunoassay, a passive hemagglutination assay, and a commercial hemagglutination inhibition test. The approximate screening levels were 10 IU/ml, 7.5 IU/ml, and 5 IU/ml, respectively. Overall seroprevalence levels varied from 76.4% screening at 15 IU to 93.1% including seropositives from any of the tests. Persons with a school record of vaccination had significantly higher seroprevalence levels than persons without records. However, only 78.3% of persons with a record had antibody greater than or equal to 15 IU compared with 60.0% without records; considering any detectable antibody, the comparison is 95.6% versus 71.4%. The low titers in vaccinees appeared to be due to a falloff of antibody with time since vaccination. Of students with a single vaccination noted in the record with exact dates, 92.3% who were vaccinated 0-4 years prior to the study had antibody at 15 IU compared with less than 78% of students with antibody who were vaccinated five or more years prior to the study. In contrast, using more sensitive assays, there was no significant decline in seroprevalence with time since vaccination. Revaccination studies and epidemiologic data suggest that almost all persons with detectable antibody whether above or below 15 IU/ml are immune to rubella. Thus, immunity levels in Massachusetts schoolchildren in the 6th, 10th, and 12th grades are probably in excess of 90%.

Pertussis epidemic in Oklahoma. Difficulties in preventing transmission.

From Jan 1 to Dec 31, 1983, 351 cases of pertussis were reported in Oklahoma. Overall, 59% of the cases were among children 3 months to 6 years of age, the target age group for pertussis vaccination; only 42% of the patients in this age group were appropriately immunized for age with diphtheria and tetanus toxoids and pertussis vaccine (DTP). A survey of 185 households in the neighborhoods of three cases found that only 65% of 57 children 3 months to 6 years of age were appropriately immunized for their age. Aggressive control of the outbreak was attempted in Oklahoma County with recommendations for widespread vaccination against pertussis. However, the effort failed to immunize 82% of the 931 children in the initial target group. Nonetheless, analysis of the reported cases suggested that less than one fourth of the cases were potentially preventable by a single additional dose of DTP, ie, in individuals 3 months to 6 years of age with a history of at least one prior dose of DTP who were not appropriately immunized for age. The optimal solution to outbreak control is outbreak prevention by ensuring that the maximal number of children younger than 7 years of age receive routine age-appropriate DTP vaccination.

Transmission of measles in medical settings. 1980 through 1984.

For the five-year period 1980 through 1984, a total of 241 persons with measles in 30 states were identified as probably having acquired their infection in a medical facility. The proportion of all measles cases acquired in medical settings increased from 0.7% for 1980 through 1982 to 2.9% for 1983 and 1984. Seventy-six percent of cases were found in patients or visitors, and 24% in personnel at the medical facility where transmission occurred. The highest proportion of cases occurred in children less than 5 years of age (54.3%), followed by persons 25 to 29 years of age (14.7%). Of spread (50.0%) and patient-to-staff spread (36.7%) were most common. Medical personnel rarely transmitted disease to others. More attention needs to be given to methods of preventing spread of measles in medical facilities, such as isolation precautions, postexposure prohylaxis of potential contacts (vaccination or immune globulin), and ensuring that medical personnel are immune to measles.

Appropriate age for measles vaccination in the United States.

The appropriate age for measles vaccination is determined by weighing the risk of measles disease and complications at a given age with vaccine efficacy at that age. In the United States, measles vaccine was initially used in children as young as 9 months of age because the disease was common and complications were greatest in persons less than 1 year of age. In 1965, when it became apparent that vaccine failure was unacceptably high in children less than 1 year and when epidemiologic analysis indicated that children greater than or equal to 1 year, particularly schoolchildren, were the primary focus of measles transmission, the vaccination age was raised to 12 months. In 1976, further studies showed efficacy was slightly higher at 15 months of age versus 12 months or 12-14 months of age. Because the risk of acquiring measles in children less than 15 months was low, the age for routine vaccination was increased to 15 months. This age recommendation may be appropriate for developed countries where the epidemiology of measles may be similar to the epidemiology in the United States. However, this age is inappropriate for many countries in the developing world where the risks of measles and complications from measles are high in young preschool children. In those countries, the recommended age for routine vaccination against measles is generally 9 months.

Immunity against measles and rubella in Massachusetts schoolchildren.

A statewide serosurvey was conducted among 6th, 10th and 12th grade Massachusetts schoolchildren in 1982. Sera were screened using a standard measles hemagglutination inhibition (HI) assay, a sensitive measles plaque neutralization assay, and four rubella assays with corresponding sensitivity limits of approximately 15, 10, 7.5, and 5 international units (IU) of rubella antibody/ml respectively. Using the most sensitive assays, seroprevalence was 98.6% for measles antibodies and 93.1% for any rubella antibodies. For persons who received single doses of either combined measles and rubella vaccines or separate single vaccinations at different times, there were no significant differences in seroprevalence using sensitive assays. Of persons who received combined vaccines, 99.3% had antibody against measles compared to 98.4% of single antigen recipients. For rubella, 98.6% of combined vaccine recipients had antibody compared to 95.7% of single antigen recipients. These seroprevalence data indicate the effectiveness of a combined vaccination program and support epidemiologic data indicating virtual elimination of these diseases in Massachusetts schoolchildren.

The virtual elimination of rubella and mumps from the United States and the use of combined measles, mumps and rubella vaccines (MMR) to eliminate measles.

The measles elimination effort, which began in 1978, has made dramatic contributions to the virtual elimination of rubella and congenital rubella syndrome (CRS) and the control of mumps in the USA. The use of combined MMR vaccine has resulted in immunization levels at school entry in excess of 95% against each of these diseases. As a result, record low levels of rubella, CRS, and mumps were reported in 1984. Continued use of MMR, along with improved surveillance and aggressive response to outbreaks, can be expected to eliminate rubella and mumps as well as measles.

Health impact of measles vaccination in the United States.

As a result of intensive efforts to vaccinate children, measles and its attendant complications of encephalitis and death have declined more than 99% from the prevaccine era. Similarly, subacute sclerosing panencephalitis has declined markedly. Measles vaccine has been demonstrated to be extremely safe, as well as extremely effective. The health and resource benefits due to vaccination against measles during the first 20 years of vaccine licensure have been enormous. In this period it is estimated that vaccination against measles has prevented 52 million cases, 5,200 deaths, and 17,400 cases of mental retardation, achieving a net savings of $5.1 billion. These substantial health and resource benefits of measles vaccination will continue to accrue in the future.

Major impediments to measles elimination. The modern epidemiology of an ancient disease.

Great success has been achieved in controlling measles in the United States with a greater than 99% reduction in incidence rate from the prevaccine era. However, since 1981, the incidence rate of measles in the United States has been relatively stable at approximately 1,500 to 3,000 reported cases annually. We reviewed available information to determine the remaining impediments to elimination of measles. The potential impediments can be divided into two categories: (1) implementation of the current strategy and (2) whether the current strategy needs modification. The major reason for the failure to achieve elimination appears to be the fact that some persons for whom vaccine is indicated have not been vaccinated. While vaccine failures and importations play a role in transmission, sustained transmission in a totally vaccinated community has not been demonstrated. All chains of transmission have involved some unvaccinated persons. Measles elimination will require complete implementation of current strategies and careful monitoring of epidemiologic trends to determine whether future modifications in strategy are needed.

Continuing measles transmission in students despite school-based outbreak control program.

FRom September 9, 1981 to January 5, 1982, a measles outbreak occurred in Warren County, Pennsylvania. The outbreak persisted for nine weeks following the implementation of a county-wide outbreak control program primarily consisting of identifying and vaccinating susceptible schoolchildren. Forty-six cases occurred among students more than two weeks after control program implementation. All 46 had a school record indicating adequate measles vaccination; 13 had been vaccinated at control program clinics by one jet-injector team (Team A). A seroprevalence survey demonstrated that persons vaccinated by Team a had a significantly higher rate of vaccination failure than children vaccinated by other teams (37.0% vs. 5.9%, p = 5.7 X 10(-7). A case-control study was undertaken to assess possible additional risk factors for developing measles. Individuals with measles were nine times more likely than control individuals to have records of measles immunization that could not be verified with providers or to have been vaccinated at 12 months of age. The most likely reasons that this outbreak was sustained among persons with adequate vaccination histories were: 1) impotent vaccines and/or improper vaccine administration techniques were used by one jet-injector team; 2) several persons with histories of adequate vaccination were really not adequately vaccinated; adn 3) a substantial number of persons had been vaccinated at 12 months of age. There is no evidence from this outbreak that transmission of measles can be sustained among the 2-10% of individuals expected to remain susceptible following a single appropriate measles vaccination.

History of convulsions and use of pertussis vaccine.

Data on 2062 reports from the Monitoring System for Adverse Events Following Immunization, Centers for Disease Control (CDC), were analyzed to compare the risk of a personal or family history of convulsions in children who had a neurologic adverse event after receipt of diphtheria-tetanus-pertussis (DTP) vaccine with those who had a nonneurologic adverse event. Children with a neurologic event after DTP vaccine had a 7.2 times higher risk for personal history of convulsions (95% confidence limits 4.5 to 11.5) and a 4.5 times higher risk for family history of convulsions (95% confidence limits 3.1 to 6.7) than did children with an adverse event that did not affect the nervous system. Children with either a febrile or nonfebrile convulsion after receipt of DTP were significantly more likely to have a personal history of convulsions than children with a nonneurologic adverse event (P less than 0.0001). Children with a febrile convulsion after receipt of DTP but not children with nonfebrile convulsions were significantly more likely to have a family history of convulsions than those with a nonneurologic adverse event. It is recommended that pertussis vaccination be deferred in children with a personal history of a convulsion until it can be determined that an evolving neurologic disorder is not present. If such disorders are found, these children should be given the combined pediatric diphtheria and tetanus toxoids (DT) vaccine to complete the series.