Evolution of Measles Elimination Strategies in the United States

Real-Time Use of a Dynamic Model To Measure the Impact of Public Health Interventions on Measles Outbreak Size and Duration - Chicago, Illinois, 2024

Measles is a highly infectious, vaccine-preventable disease that can cause severe illness, hospitalization, and death. A measles outbreak associated with a migrant shelter in Chicago occurred during February-April 2024, in which a total of 57 confirmed cases were identified, including 52 among shelter residents, three among staff members, and two among community members with a known link to the shelter. CDC simulated a measles outbreak among shelter residents using a dynamic disease model, updated in real time as additional cases were identified, to produce outbreak forecasts and assess the impact of public health interventions. As of April 8, the model forecasted a median final outbreak size of 58 cases (IQR = 56-60 cases); model fit and prediction range improved as more case data became available. Counterfactual analysis of different intervention scenarios demonstrated the importance of early deployment of public health interventions in Chicago, with a 69% chance of an outbreak of 100 or more cases had there been no mass vaccination or active case-finding compared with only a 1% chance when those interventions were deployed. This analysis highlights the value of using real-time, dynamic models to aid public health response, set expectations about outbreak size and duration, and quantify the impact of interventions. The model shows that prompt mass vaccination and active case-finding likely substantially reduced the chance of a large (100 or more cases) outbreak in Chicago.

Understanding the challenges to COVID-19 vaccines and treatment options, herd immunity and probability of reinfection

Unlike pandemics in the past, the outbreak of coronavirus disease 2019 (COVID-19), which rapidly spread worldwide, was met with a different approach to control and measures implemented across affected countries. The lack of understanding of the fundamental nature of the outbreak continues to make COVID-19 challenging to manage for both healthcare practitioners and the scientific community. Challenges to vaccine development and evaluation, current therapeutic options, convalescent plasma therapy, herd immunity, and the emergence of reinfection and new variants remain the major obstacles to combating COVID-19. This review discusses these challenges in the management of COVID-19 at length and highlights the mechanisms needed to provide better understanding of this pandemic.

Mapping the global opinion space to explain anti-vaccine attraction

Vaccines save millions of lives every year. They are recommended by experts, trusted by the majority of people, and promoted by expensive health campaigns. Even so, people with neutral attitudes are more persuaded by people holding anti-vaccine than pro-vaccine attitudes. Our analysis of vaccine-related attitudes in more than 140 countries makes sense of this paradox by including approaches from social influence. Specifically, we show that neutral people are positioned closer to anti- than to pro-vaccine people in the opinion space, and therefore more persuadable by them. We use dynamic social simulations seeded with vaccine survey data, to show how this effect results in a drift towards anti-vaccine opinions. Linking this analysis to data from two other multi-country datasets, we found that countries in which the pro-vaccine people are less associated to the neutrals (and so less able to influence them) exhibit lower vaccination rates and stronger increase in distrust. We conclude our paper by showing how taking social influence into account in vaccine-related policy-making can possibly reduce waves of distrust towards vaccination.

Challenges in Establishing Vaccine Induced Herd Immunity through Age Specific Community Vaccinations

Presently, the second wave of COVID-19 pandemic is driving the world towards a devastating total failure of the healthcare system. The purpose of the review is to search for the studies reporting on the implication of herd immunity into a naïve population through age specific mass vaccination. This review is based on selected publications on the effect herd immunity to COVID 19 in communities. We searched published scientific articles, review articles, reports, published in 2020 as well as read some basic, cult publications related to establishment of indirect immunity to a population. We have focused on use of application of vaccine induced herd immunity into community to confer indirect immunity against COVID-19 and searched on electronic databases, including PubMed (http://www.pubmed.com), Scopus (http://www.scopus.com), Google Scholar (http://www.scholar.google.com), Web of Science (www.webofscience.com) and Science Direct by using key words such as Herd immunity, indirect or passive immunization, Coronavirus disease 2019 (COVID-19), severe acute respiratory syndrome, coronavirus 2 (SARS-CoV-2), and immune-technique. This review proposes the implication of mass vaccination-induced herd immunity in a population to curb the infection, and to every individual in a given population irrespective of their age.

Mathematical Modeling of Endemic Cholera Transmission

Mathematical modeling can be used to project the impact of mass vaccination on cholera transmission. Here, we discuss 2 examples for which indirect protection from mass vaccination needs to be considered. In the first, we show that nonvaccinees can be protected by mass vaccination campaigns. This additional benefit of indirect protection improves the cost-effectiveness of mass vaccination. In the second, we model the use of mass vaccination to eliminate cholera. In this case, a high population level of immunity, including contributions from infection and vaccination, is required to reach the “herd immunity” threshold needed to stop transmission and achieve elimination.

Immunosuppression Does Not Affect Antibody Concentrations to Measles, Mumps, and Rubella in Patients with Inflammatory Bowel Disease

BACKGROUND

The Advisory Committee on Immunization Practices (ACIP) recommends using the immunization record and not serologic testing to determine immunity against measles and rubella in the general population, due to potential false negatives. However, it is unknown whether the immune response is less durable among patients who are immunosuppressed.

AIMS

The primary aim of this study was to evaluate sustained vaccine-induced measles, mumps, and rubella (MMR) antibody concentrations in immunosuppressed patients with inflammatory bowel disease (IBD).

METHODS

We performed a cross-sectional study to compare antibody concentrations following the two-dose (MMR) vaccine among 46 patients with IBD and 20 healthy controls (HC). Three IBD groups stratified by the immunosuppressive regimen that preceded study entry for at least 3 months: (1) thiopurine monotherapy, (2) anti-TNF monotherapy, or (3) combination therapy (anti-TNF agent combined with an immunomodulator) were enrolled.

RESULTS

All subjects had measurable antibody concentrations to the three vaccine viruses. Age and time since receipt of MMR series were similar in both groups. There were no difference in the antibody concentration of measles (IBD 667 mIU/ml vs HC 744 mIU/ml; p = 0.45), mumps (IBD 339 EU/ml vs HC 402 EU/ml; p = 0.62), or rubella (IBD 25 mIU/ml vs HC 62 mIU/ml; p = 0.11) among the groups. No differences in antibody concentrations were found among the IBD treatment groups.

CONCLUSION

Immunosuppressed patients with IBD have sustained antibody concentrations comparable to healthy controls. Thus, gastroenterologist should follow the ACIP recommendations and use the immunization record when available to determine immunity to measles and rubella in patients with IBD. Clinical Trials Registry # NCT02434133.

A Case of Early Onset Subacute Sclerosing Panencephalitis Presented as Juvenile Myoclonic Epilepsy

A 7.5 years girl presented with myoclonic jerks with prolonged duration coming progressively at shorter intervals for last six moinths. There was declining academic performances. The dystonic, dyskinetic movements and ataxia were there for last three months. The stages were progressing too rapidly. IgG antibody titre to measles virus was found to be positive with EEG changes which confirms diagnosis. SSPE at so early age with atypical presentation is unique in this indexed case.

Emerging and Neglected Infectious Diseases: Insights, Advances, and Challenges

Infectious diseases are a significant burden on public health and economic stability of societies all over the world. They have for centuries been among the leading causes of death and disability and presented growing challenges to health security and human progress. The threat posed by infectious diseases is further deepened by the continued emergence of new, unrecognized, and old infectious disease epidemics of global impact. Over the past three and half decades at least 30 new infectious agents affecting humans have emerged, most of which are zoonotic and their origins have been shown to correlate significantly with socioeconomic, environmental, and ecological factors. As these factors continue to increase, putting people in increased contact with the disease causing pathogens, there is concern that infectious diseases may continue to present a formidable challenge. Constant awareness and pursuance of effective strategies for controlling infectious diseases and disease emergence thus remain crucial. This review presents current updates on emerging and neglected infectious diseases and highlights the scope, dynamics, and advances in infectious disease management with particular focus on WHO top priority emerging infectious diseases (EIDs) and neglected tropical infectious diseases.

Improving the Science of Measles Prevention-Will It Make for a Better Immunization Program?

In a Perspective, Julie Garon and Walter Orenstein discuss Lessler and colleagues' modeling study on measles vaccination and the implications for triggered and routine immunization programs.

Measles

Measles is an infectious disease in humans caused by the measles virus (MeV). Before the introduction of an effective measles vaccine, virtually everyone experienced measles during childhood. Symptoms of measles include fever and maculopapular skin rash accompanied by cough, coryza and/or conjunctivitis. MeV causes immunosuppression, and severe sequelae of measles include pneumonia, gastroenteritis, blindness, measles inclusion body encephalitis and subacute sclerosing panencephalitis. Case confirmation depends on clinical presentation and results of laboratory tests, including the detection of anti-MeV IgM antibodies and/or viral RNA. All current measles vaccines contain a live attenuated strain of MeV, and great progress has been made to increase global vaccination coverage to drive down the incidence of measles. However, endemic transmission continues in many parts of the world. Measles remains a considerable cause of childhood mortality worldwide, with estimates that >100,000 fatal cases occur each year. Case fatality ratio estimates vary from <0.01% in industrialized countries to >5% in developing countries. All six WHO regions have set goals to eliminate endemic transmission of MeV by achieving and maintaining high levels of vaccination coverage accompanied by a sensitive surveillance system. Because of the availability of a highly effective and relatively inexpensive vaccine, the monotypic nature of the virus and the lack of an animal reservoir, measles is considered a candidate for eradication.

Synthesis of Evidence to Characterize National Measles and Rubella Exposure and Immunization Histories

Population immunity depends on the dynamic levels of immunization coverage that countries achieve over time and any transmission of viruses that occur within the population that induce immunity. In the context of developing a dynamic transmission model for measles and rubella to support analyses of future immunization policy options, we assessed the model inputs required to reproduce past behavior and to provide some confidence about model performance at the national level. We reviewed the data available from the World Health Organization (WHO) and existing measles and rubella literature for evidence of historical reported routine and supplemental immunization activities and reported cases and outbreaks. We constructed model input profiles for 180 WHO member states and three other areas to support disease transmission model development and calibration. The profiles demonstrate the significant variability in immunization strategies used historically by regions and member states and the epidemiological implications of these historical choices. The profiles provide a historical perspective on measles and rubella immunization globally at the national level, and they may help immunization program managers identify existing immunity and/or knowledge gaps.

Modeling Measles Transmission in the North American Amish and Options for Outbreak Response

Measles outbreaks in the United States continue to occur in subpopulations with sufficient numbers of undervaccinated individuals, with a 2014 outbreak in Amish communities in Ohio pushing the annual cases to the highest national number reported in the last 20 years. We adapted an individual-based model developed to explore potential poliovirus transmission in the North American Amish to characterize a 1988 measles outbreak in the Pennsylvania Amish and the 2014 outbreak in the Ohio Amish. We explored the impact of the 2014 outbreak response compared to no or partial response. Measles can spread very rapidly in an underimmunized subpopulation like the North American Amish, with the potential for national spread within a year or so in the absence of outbreak response. Vaccination efforts significantly reduced the transmission of measles and the expected number of cases. Until global eradication, measles importations will continue to pose a threat to clusters of underimmunized individuals in the United States. Aggressive outbreak response efforts in Ohio probably prevented widespread transmission of measles within the entire North American Amish.

The Reemergence of Measles

Measles, or rubeola, is a highly infectious, acute viral illness of childhood that is considered eliminated in the USA but has reemerged in the past few years. Globally, an estimated 20 million cases of measles continue to occur, and it remains a leading cause of death among young children. It is rare in the USA and other first world countries, but numerous outbreaks have occurred in the USA recently, due to a combination of factors including poor vaccine coverage and importation of cases among travelers returning from endemic areas. The diagnosis of measles is usually made clinically, when an individual presents with a constellation of symptoms including cough, coryza, conjunctivitis, high fever, and an erythematous maculopapular rash in a cephalocaudal distribution. Complications are common and include otitis media, pneumonia, encephalitis, and rarely death. A measles vaccine is available in two doses and provides excellent protection against the disease. Despite this, vaccination coverage, especially among young adults, remains poor. Given its resurgence in the USA and other countries, interventions are urgently needed to address low vaccination rates and vaccine hesitancy. Measles awareness should also be a priority among young clinicians, who may have never seen a case or are not familiar with the disease.

An assessment of measles vaccine effectiveness, Australia, 2006-2012

OBJECTIVE

Vaccine effectiveness analysis serves as a critical evaluation for immunization programmes and vaccination coverage. It also contributes to maintaining public confidence with the vaccine providers. This study estimated measles vaccine effectiveness at the population level using Australian national notifications data between 2006 and 2012.

METHODS

Notification data were obtained from the National Notifiable Diseases Surveillance System. Vaccination status was classified according to whether a case had received zero, one or two doses of measles-containing vaccine. Cases aged less than 1 year and those with unknown vaccination status were excluded. All children with disease onset between 1 January 2006 and 31 December 2012 who were born after 1996 were included. Cases were matched to controls extracted from the Australian Childhood Immunization Register according to date of birth and jurisdiction of residence. Vaccine effectiveness was estimated by conditional logistic regression. Sensitivity analyses were conducted to test data robustness.

RESULTS

Vaccine effectiveness was estimated at 96.7% (95% confidence interval [CI]: 94.5-98.0%) for one dose and 99.7% (95% CI: 99.2-99.9%) for two doses of measles vaccine. For at least one dose, effectiveness was estimated at 98.7% (95% CI: 97.9-99.2%). Sensitivity analyses did not significantly alter the base estimates.

DISCUSSION

Vaccine effectiveness estimates suggested that the measles vaccine was protective at the population level between 2006 and 2012. However, vaccination coverage gaps may have contributed to recent measles outbreaks and may represent a serious barrier for Australia to maintain measles elimination status.

Long-term measles-induced immunomodulation increases overall childhood infectious disease mortality

Immunosuppression after measles is known to predispose people to opportunistic infections for a period of several weeks to months. Using population-level data, we show that measles has a more prolonged effect on host resistance, extending over 2 to 3 years. We find that nonmeasles infectious disease mortality in high-income countries is tightly coupled to measles incidence at this lag, in both the pre- and post-vaccine eras. We conclude that long-term immunologic sequelae of measles drive interannual fluctuations in nonmeasles deaths. This is consistent with recent experimental work that attributes the immunosuppressive effects of measles to depletion of B and T lymphocytes. Our data provide an explanation for the long-term benefits of measles vaccination in preventing all-cause infectious disease. By preventing measles-associated immune memory loss, vaccination protects polymicrobial herd immunity.

Measles vaccine coverage estimates in an outbreak three years after the nation-wide campaign in China: implications for measles elimination, 2013

Background

China is approaching measles elimination, but indigenous measles still circulates. County L in China has reported measles-containing vaccine (MCV) coverage rates >95% since 2000. Despite high reported coverage, a large measles outbreak occurred among young children in L County. We measured MCV coverage using 5 different methods during an investigation on this outbreak and compared our estimates with reported rates.

Methods

Reported coverage rates are determined by aggregating clinic-based data across the county: doses administered in each clinic divided by the number of children registered in each clinic. Our methods estimated coverage for the 2010–2012 birth cohort, and were (1) administrative method: doses administered in clinics divided by the birth cohort recorded in the Statistical Year Book, (2) house-to-house convenience-sample survey of children living near cases, (3) vaccination clinic records review, (4) determination of a convenience sample of measles outbreak cases’ vaccination statuses and using the field vaccine efficacy outbreak equation to estimate population coverage, and (5) a seroprevalence survey using a convenience sample of residual blood samples from hospitals.

Results

The measles outbreak totaled 215 cases, representing an incidence of 195.8 per million population. Our estimated MCV coverage rates were: (1) administrative method: 84.1%-87.0% for MCV1 and 80.3%-90.0% for MCV2, (2) in-house survey: 83.3% of 9–17 month children received MCV1, and 74.5% of 24–47 month children received MCV2, (3) clinic record review: 85.5% of 9–17 month children received MCV1, and 73.2% of 24–59 month children received MCV2, (4) field VE method: 83.6% of 9–47 month children received one or more MCV doses, and (5) serology: seropositive rates were <80% in the 12–17 and 18–23 month age cohorts.

Conclusions

Compared with reported coverage >95%, our 5 coverage assessments all showed substantially lower coverage. China should evaluate guidelines for reporting vaccination coverage and identify feasible improvements to the assessment methods.

Enabling implementation of the Global Vaccine Action Plan: developing investment cases to achieve targets for measles and rubella prevention

Global prevention and control of infectious diseases requires significant investment of financial and human resources and well-functioning leadership and management structures. The reality of competing demands for limited resources leads to trade-offs and questions about the relative value of specific investments. Developing investment cases can help to provide stakeholders with information about the benefits, costs, and risks associated with available options, including examination of social, political, governance, and ethical issues. We describe the process of developing investment cases for globally coordinated management of action plans for measles and rubella as tools for enabling the implementation of the Global Vaccine Action Plan (GVAP). We focus on considerations related to the timing of efforts to achieve measles and rubella goals independently and within the context of ongoing polio eradication efforts, other immunization priorities, and other efforts to control communicable diseases or child survival initiatives. Our analysis suggests that the interactions between the availability and sustainability of financial support, sufficient supplies of vaccines, capacity of vaccine delivery systems, and commitments at all levels will impact the feasibility and timing of achieving national, regional, and global goals. The timing of investments and achievements will determine the net financial and health benefits obtained. The methodology, framing, and assumptions used to characterize net benefits and uncertainties in the investment cases will impact estimates and perceptions about the value of prevention achieved overall by the GVAP. We suggest that appropriately valuing the benefits of investments of measles and rubella prevention will require the use of integrated dynamic disease, economic, risk, and decision analytic models in combination with consideration of qualitative factors, and that synthesizing information in the form of investment cases may help stakeholders manage expectations as they chart the course ahead and navigate the decade of vaccines.

Monitoring progress towards the elimination of measles in China: an analysis of measles surveillance data

OBJECTIVE

To analyse the epidemiology of measles in China and determine the progress made towards the national elimination of the disease.

METHODS

We analysed measles surveillance data - on the age, sex, residence and vaccination status of each case and the corresponding outcome, dates of onset and report and laboratory results - collected between January 2005 and October 2013.

FINDINGS

Between 2005 and October 2013, 596 391 measles cases and 368 measles-related deaths were reported in China. Annual incidence, in cases per 100 000 population, decreased from 9.95 in 2008 to 0.46 in 2012 but then rose to more than 1.96 in 2013. The number of provinces that reported an annual incidence of less than one case per million population increased from one in 2009 to 15 in 2012 but fell back to one in 2013. Median case age decreased from 83 months in 2005 to 14 months in 2012 and 11 months in January to October 2013. Between 2008 and 2012, the incidence of measles in all age groups, including those not targeted for vaccination, decreased by at least 93.6%. However, resurgence started in late 2012 and continued into 2013. Of the cases reported in January to October 2013, 40% were aged 8 months to 6 years.

CONCLUSION

Although there is evidence of progress towards the elimination of measles from China, resurgence in 2013 indicated that many children were still not being vaccinated on time. Routine immunization must be strengthened and the remaining immunity gaps need to be identified and filled.

Measles virus and associated central nervous system sequelae

Worldwide, measles remains one of the most deadly vaccine-preventable diseases. In the United States, enrollment in the public schools requires that each child receives 2 doses of measles-containing vaccine before entry, essentially eliminating this once endemic disease. Recent outbreaks of measles in the United States have been associated with importation of measles virus from other countries and subsequent transmission to intentionally undervaccinated children. The central nervous system complications of measles can occur within days or years of acute infection and are often severe. These include primary measles encephalitis, acute postinfectious measles encephalomyelitis, measles inclusion body encephalitis, and subacute sclerosing panencephalitis. These measles-associated central nervous system diseases differ in their pathogenesis and pathologic effects. However, all involve complex brain-virus-immune system interactions, and all can lead to severe and permanent brain injury. Despite better understanding of the clinical presentations and pathogenesis of these illnesses, effective treatments remain elusive.

Impact of supplementary immunization activities in measles-endemic areas: a case study from Guangxi, China

Because of limited resources, each year during the period from 1999 through 2007, only about one-quarter of the 111 counties in Guangxi province were selected by means of risk assessment to participate in Supplementary Immunization Activities (SIAs), targeting children aged 8 months to 14 years during 1999-2003 and 8 months to 10 years during 2004-2007. Approximately 2 million doses of measles vaccines were administrated each year during SIAs. Estimated from the National Notifiable Diseases Surveillance System, with a reliable internal consistency over years, the average annual incidences of measles before SIAs (1993-1998), during the first phase (1999-2003), and during the second phase (2004-2007) were 16.05, 9.10, and 2.46 cases per 100,000, respectively. The overall provincewide annual incidence decreased by 84.67%, from 12.12 cases per 100,000 in 2000 to 2.10 cases per 100,000 in 2007. The percentage of counties with annual incidence ≥10 cases per 100,000 decreased from 55% in 1993 to <1% in 2007. Compared with the pre-SIA period, the greatest decrease in annual incidence was 83.93% for the 10-14.9-year-old group and the smallest decrease was 46.16% for children <1 year old. The multiple-year SIAs targeting children in selected high-risk counties were effective in controlling measles in mountainous, impoverished, and multiethnic measles-endemic areas.

Further efforts needed to achieve measles elimination in Germany: results of an outbreak investigation

OBJECTIVE

To determine morbidity and costs related to a large measles outbreak in Germany and to identify ways to improve the country's national measles elimination strategy.

METHODS

We investigated a large outbreak of measles in the federal state of North Rhine-Westphalia (NRW) that occurred in 2006 after 2 years of low measles incidence (< 1 case per 100,000). WHO's clinical case definition was used, and surveillance data from 2006 and 2001 were compared. All cases notified in Duisburg, the most severely affected city, were contacted and interviewed or sent a questionnaire. Health-care provider costs were calculated using information on complications, hospitalization and physician consultations.

FINDINGS

In NRW, 1749 cases were notified over a 48-week period. Compared with 2001, the distribution of cases shifted to older age groups (especially the 10-14 year group). Most cases (n = 614) occurred in Duisburg. Of these, 81% were interviewed; 15% were hospitalized and two died. Of the 464 for whom information was available, 80% were reported as unvaccinated. Common reasons for non-vaccination were parents either forgetting (36%) or rejecting (28%) vaccination. The average cost per measles case was estimated at 373 euros.

CONCLUSION

An accumulation of non-immune individuals led to this outbreak. The shift in age distribution has implications for the effectiveness of measles control and the elimination strategy in place. Immediate nationwide school-based catch-up vaccination campaigns targeting older age groups are needed to close critical immunity gaps. Otherwise, the elimination of measles in Germany and thus in Europe by 2010 will not be feasible.

Seroprevalence of measles antibody in the US population, 1999-2004

BACKGROUND

Endemic measles transmission was declared eliminated in the United States in 2000. To ensure that elimination can be maintained, high population immunity must be sustained and monitored. Testing for measles antibody was included in the National Health and Nutrition Examination Survey (NHANES), a nationally representative survey, conducted during 1999-2004.

METHODS

A measles-specific immunoassay was used to measure the seroprevalence of measles antibody in NHANES participants 6-49 years of age. For analysis, participants were grouped by birth cohort.

RESULTS

During 1999-2004, the rate of measles seropositivity in the population overall was 95.9% (95% confidence interval [CI], 95.1%-96.5%). The highest seroprevalence of measles antibody was in non-Hispanic blacks (98.6% [95% CI, 98.0%-99.1%]). Those born during 1967-1976 had significantly lower levels of measles antibody (92.4% [95% CI, 90.8%-93.9%]) than did the other birth cohorts. Independent predictors of measles seropositivity in the 1967-1976 birth cohort were non-Hispanic/black race/ethnicity, more than a high school education, having health insurance, and birth outside the United States.

CONCLUSIONS

Measles seropositivity was uniformly high in the US population during 1999-2004. Nearly all population subgroups had evidence of measles seropositivity levels greater than the estimated threshold necessary to sustain measles elimination. Non-Hispanic whites and Mexican Americans born during 1967-1976 had the lowest measles seropositivity levels and represent populations that might be at increased risk for measles disease if the virus were reintroduced into the United States.

The role of measles elimination in development of a national immunization program

The U.S. Immunization Program has been one of the most successful efforts in preventive medicine. Since its beginning with passage of the Vaccination Assistance Act in 1962, polio, measles and rubella have been eliminated and many other vaccine-preventable diseases are at record or near record lows. In 1966, 3 years after licensure of the first measles vaccines, the Centers for Disease Control and Prevention began an effort to eliminate measles within the United States, an on-and-off effort that was to last more than 30 years. With measles elimination as the primary driver, fundamental components of today's immunization program were built that affected not only measles, but all of the vaccines and vaccine-preventable diseases of childhood. Some of the major contributions were the enactment and enforcement of immunization requirements for school attendance in all 50 states, enactment of an entitlement program for vaccine purchase, the Vaccines for Children Program, support for health services research to determine reasons for nonimmunization and interventions to improve coverage, development of standards for immunization practices and the measurement system for immunization coverage in all 50 states and 28 major urban areas. Key lessons have been: (1) the program must rest on a sound base of vaccine science and health services science; (2) having a limited number of measurable goals allows program focus, but consider strategies that have crosscutting impact; (3) accountability is critical to program performance at all levels-state, local and individual practice; and (4) establishing and maintaining political support is essential.

Efforts at Rubella Elimination in the United States: The Impact of Hemispheric Rubella Control

We examined rubella vaccination trends, rubella surveillance, and disease patterns for the Americas, Mexico, and the United States, to evaluate the impact of hemispheric rubella control on rubella elimination in the United States during 1997-2004. In 1997, 130,375 rubella cases were reported in the Americas, with 38,042 reported in Mexico. Over the next 7 years, a rubella control initiative resulted in the administration of approximately 110 million rubella-containing vaccine doses in Latin America, with 77.7 million doses administered within Mexico. By 2004, the number of reported rubella cases had declined to 3103 in the Americas and 698 in Mexico. Concurrently, the number of rubella cases in the United States fell from 817 during 1997-1999 to <25 cases/year from 2001 onward, with loss of seasonality and geographic clustering, despite no change in vaccination rates. Implementation of rubella control strategies in the Americas, particularly in Mexico, appears to have facilitated rubella elimination in the United States.

Has the United States Population Been Adequately Vaccinated to Achieve Rubella Elimination?

Mathematical models indicate that elimination of rubella virus transmission requires maintenance of approximately 90% rubella immunity among children. To evaluate whether rubella vaccination coverage among US preschool and school-age children is at levels consistent with rubella elimination, we reviewed data from 3 sources: (1) the Biologics Surveillance, which documents the net number of vaccine doses sold (1970-2004); (2) state immunization surveys of school entrants 5-6 years of age (1980-2005); and (3) the National Immunization Survey of children 19-35 months of age (1995-2004). Vaccine biologics data show that the net number of rubella vaccine doses sold was at least equivalent to the number of children born each year during 1970-2004. The average coverage for school-entrant surveys among reporting states was >95% for 1980-2004. National coverage among children 19-35 months of age was > or =90% overall for each year during 1995-2004. Three independent surveys suggest that childhood coverage with rubella-containing vaccine has been at sufficiently high levels to achieve elimination of rubella virus transmission.

Improving immunization rates in practice settings

Many pediatricians do not know the immunization rate of patients in their practice. Evidence-based standards of practice have been established, leading to improved rates. Quality improvement efforts aimed at immunization are effective and may lead to improvement in other preventive health services. By providing more vaccines in the medical home, communities can decrease the need for higher cost case management and outreach services targeting patients with delayed immunizations.

A limited measles outbreak in a highly vaccinated US boarding school

OBJECTIVES

We investigated a measles outbreak that began in March 2003 in a Pennsylvania boarding school with >600 students to identify all cases, including the source; implement outbreak control measures; and evaluate vaccine effectiveness.

METHODS

Measles was suspected in any person at the school with a generalized rash and fever during March 21 to May 28, 2003 and investigated with serologic testing. We reviewed vaccination history from school records and conducted a survey to determine country of measles vaccination. Vaccine effectiveness was calculated using the cohort method.

RESULTS

We identified 9 laboratory-confirmed cases at the school: 8 students and 1 staff member. Among them, 2 had never received any doses of measles-containing vaccine (MCV), 1 received 1 dose of MCV, and 6 received 2 doses of MCV. Three of the 6 who received 2 doses of MCV received both doses outside the United States. The source case had been infected in Lebanon. Two laboratory-confirmed spread cases were identified in New York City. Measles virus of genotype D4 was isolated in cases from the school and New York City. Of the 663 students in the school, 8 (1.2%) had never received any doses of MCV, 26 (3.9%) had received 1 dose, and 629 (94.9%) had received 2 doses before the outbreak. Vaccine effectiveness among students who had received 2 doses of MCV was 98.6%. However, students who received both doses outside the United States had a higher attack rate (3 of 75) than those who received both doses in the United States (3 of 509; rate ratio: 6.8; 95% confidence interval: 1.4-33.0).

CONCLUSIONS

This is the largest measles outbreak to occur in a school in the United States since 1998, but it was limited to only 9 cases in a boarding school with >600 students. The limited extent of this outbreak highlights the high level of population immunity achieved in the United States through widespread implementation of a 2-dose measles-mumps-rubella vaccination strategy in school-aged children. States and schools should continue to enforce strictly the 2-dose measles-mumps-rubella vaccination requirement and, in an outbreak setting, consider revaccinating students who received measles vaccine outside of the United States. Continued vigilance by health care providers is needed to recognize measles cases.

Population Immunity to Measles in the United States, 1999

To estimate population immunity, we examined measles immunity among residents of the United States in 1999 from serological and vaccine coverage surveys. For persons aged >or=20 years, serological data from the third National Health and Nutrition Examination Survey (1988-1994) were used. For persons <20 years of age, immunity was estimated from results of the National Immunization Survey (1994-1998), state surveys of school entrants (1990-2000), and vaccine coverage surveys of adolescents (1997). To estimate immunity from vaccine coverage data, 95% vaccine efficacy was used for recipients of a single dose at >or=12 years of age and 99% vaccine efficacy was used for those with failure of a first dose who were revaccinated. Overall, calculated population immunity was found to be 93%. Although there was not much variation in immunity by region and state, in some large urban centers immunity among preschool-aged children was as low as 86%. Overall, geographic- and age-specific estimates of a high population immunity support the epidemiological evidence that measles disease is no longer endemic in the United States.