Vaccination levels associated with lack of measles transmission among preschool-aged populations in the United States, 1989-1991

Knowledge of the minimum level of vaccination capable of preventing measles transmission in an age group is helpful for establishing program targets for measles elimination. In 1990, during the measles resurgence in the United States, one-half of cases occurred in children aged <5 years. Although estimated population immunity among persons >or=6 years of age was 93%, immunity was lower and varied widely among preschool-aged children. To examine the association of vaccine coverage at 2 years of age and measles incidence among preschool-aged children, we analyzed ecological studies of measles incidence in Milwaukee (Wisconsin) census tracts, Dallas (Texas) ZIP code areas, and selected cities during the 1989-1991 measles resurgence. In each study area, measles incidence decreased rapidly with increasing measles vaccine coverage and became low or negligible when coverage was >or=80%. Regression analysis also suggested that measles would not be transmitted when vaccine coverage was at least 79%. A minimum vaccine coverage of approximately 80% at the second birthday in census tracts, ZIP code areas, and cities in the United States may be sufficient to prevent measles transmission among preschool-aged children if population immunity is >or=93% among persons >or=6 years of age.     

Measles epidemiology and elimination strategies in Turkey

In Turkey, 15,000-30,000 measles cases have been reported annually since the 1990s. Epidemics occur every 3-4 years, and >/=90% of cases are <15 years old. The high incidence is due to inadequate vaccination coverage (nationally 84% in 2001) and immunity provided by the first dose of vaccine administered at age 9 months. The second dose, which has been recommended for first grade students since 1998, has been insufficient to provide the herd immunity necessary to control measles. The Ministry of Health launched a comprehensive program for 2002-2010 targeting measles elimination. This plan calls for a national vaccination campaign among all children aged 9 months to 14 years and routine two-dose vaccination coverage will be increased to >/=95% or follow-up campaigns will be conducted in areas not achieving high coverage levels. Also, all military recruits in 2002-2009 will be vaccinated and case-based, laboratory supported surveillance will be initiated.     

Progress toward interruption of endemic measles transmission in Tunisia

Measles was the second leading cause of infant mortality in Tunisia prior to introduction of measles vaccination in 1979. The number of reported measles cases has decreased from 3007 in 1981 to 47 cases in 2000 due in part to the high coverage rates achieved after 1992. During 1998, a measles catch-up campaign vaccinated 1,846,657 children (95%) aged 6-16 years, and a follow-up campaign for children aged 9 months to 5 years in 2001 reached 547,766 (94%). During 1999-2001, 1717 cases of rash and fever illness were tested for measles; only 3 (0.2%) were positive for measles. From February to July 2002, an outbreak of measles involving 87 cases occurred in Tunisia in a health care setting and 56 (64%) patients were aged 15-30 years. The low number of laboratory-confirmed measles cases during 1999-2001 suggests endemic measles transmission may have been interrupted.     

Implementation of a mass measles campaign in central Afghanistan,December 2001 to May 2002

In Afghanistan health services have been disrupted by 23 years of conflict and 1 of 4 children die before age 5 years. Measles accounts for an estimated 35,000 deaths annually. Surveillance data show a high proportion of measles cases (38%) among those >/=5 years old. In areas with complex emergencies, measles vaccination is recommended for those aged 6 months to 12-15 years. From December 2001 to May 2002, Afghan authorities and national and international organizations targeted 1,748,829 children aged 6 months to 12 years in five provinces in central Afghanistan for measles vaccinations. Two provinces reported coverage of >90% and two >80%. Coverage in Kabul city was 62%. A subsequent cluster survey in the city found 91% coverage (95% confidence interval [CI], 0.85-0.91) among children 6-59 months and 88% (95% CI, 0.87-0.95) among those 5-12 years old. Thus, this campaign achieved acceptable coverage despite considerable obstacles.     

Impact of nationwide measles vaccination campaign among children aged 9 months to 14 years,Zimbabwe, 1998-2001

Zimbabwe (population 11,365,000) introduced nationwide one-dose measles vaccination in 1981. This strategy reached 70%-80% of infants <1 year of age over the next two decades; in 1998, a nationwide supplemental immunization activity (SIA) targeting all children aged 9 months to 14 years achieved 93% coverage. Surveillance data were examined to determine the impact of these strategies. During 1985-1997, there were 8529-49,812 measles cases annually. After the SIA, laboratory confirmation of the first 5 outbreak cases and all sporadic cases was required. In 1999 and 2000, 1343 (88%) of 1534 suspected cases had adequate specimens submitted and 28 (2%) were measles IgM positive. In 2001, of 529 suspected cases, 513 (97%) had adequate specimens and only 7 (1%) were measles IgM positive. These data suggest that indigenous measles transmission in Zimbabwe has been interrupted and that high prevalence of human immunodeficiency virus seropositivity does not hinder vaccination-induced measles control. High vaccination coverage obtained through the routine health care system supplemented by periodic follow-up SIAs will be required to maintain low transmission levels.     

Impact of alternative approaches to accelerated measles control: experience in the African region, 1996-2002

From 1996 to 2000, several African countries accelerated measles control by providing a second opportunity for measles vaccine through supplemental campaigns. Fifteen countries completed campaigns in children aged 9 months to 14 years. Seven countries completed campaigns in children aged 9-59 months. In almost all countries that conducted campaigns in children aged 9 months to 14 years, measles deaths were reduced to near zero. In six countries, near-zero measles mortality has been maintained for 4-6 years. Supplemental immunization in children <5 years old was only partially effective (range, 0-67%) in reducing mortality. Measles cases decreased by 50% when routine vaccination coverage increased from 50% to 80%. Initial measles campaigns in children aged 9 months to 14 years, follow-up campaigns in those aged 9-59 months every 3-5 years, and increased routine coverage to 80% will be needed to reduce and maintain measles deaths in African countries at near zero.     

Successful control and impending elimination of measles in the Islamic Republic of Iran

Measles is still one of the most common infectious killers of children in the world, especially in developing countries. In Iran, during the prevaccine era, 150,000-500,000 cases of measles were reported annually, with a death rate of 10%-15%. After the establishment of Expanded Program on Immunization program in 1984, vaccination rates for the first and second doses of measles vaccine increased to >90% by the mid-1990s, and the number of measles cases decreased to 2652 in 1996. In response to increased numbers of cases in older age groups during 1996-2002, a nationwide measles-rubella vaccination campaign was conducted in 2003, and 33,100,000 persons (99%) aged 5-25 years were vaccinated. During 2004-2009, 221 laboratory-confirmed measles cases (<1 case per million population) were detected, primarily in rural areas and among migrant groups who traveled to or came from high-incidence countries. High routine immunization coverage, low disease incidence, and surveillance system data suggest that interruption of endemic virus transmission might have already been achieved in Iran, but challenges remain and continued efforts are needed to sustain this accomplishment.     

Closer to the goal: efforts in measles elimination in Germany 2010

Increasing 2-dose vaccination coverage has led to an interruption of endemic measles virus circulation in Germany. However, outbreaks after virus importation still occur and contribute to international transmission chains. Between 2003 and 2009, annual measles incidence ranged between 0.2 and 2.8 per 100,000 population. Immunization gaps have been identified especially in secondary-school students and young adults, which is also reflected by a shift in age distribution of reported measles cases toward older age groups. Stronger political commitment and standardized guidelines for outbreak containment were put in place in Germany in the past years, but the last step toward measles elimination cannot be made until the number of susceptible individuals has been further reduced. In addition to routine childhood vaccination, supplementary immunization activities are needed targeting school students and young adults to close critical immunization gaps. Intensification of public awareness and sound information on vaccinations are necessary to convince skeptics and remind the forgetful.     

Impact of mass measles campaigns among children less than 5 years old in Uganda

In 1999-2001, a national measles control strategy was implemented in Uganda, including routine immunization and mass vaccination campaigns for children aged 6 months to 5 years. This study assesses the impact of the campaigns on measles morbidity and mortality. Measles cases reported from 1992 through 2001 were obtained from the Health Management Information System, and measles admissions and deaths were assessed in six sentinel hospitals. Measles incidence declined by 39%, measles admissions by 60%, and measles deaths by 63% in the year following the campaigns, with impact lasting 15 to 22 months. Overall, 64% of measles cases were among children <5 years of age, and 93% were among children 相似文献   

Evolution of measles elimination strategies in the United States

There have been 3 efforts to eliminate measles from the United States since the introduction of measles vaccine in 1963. To date, 10 major lessons have been learned from elimination efforts. First, elimination requires very high vaccination-coverage levels by age 2 years. Second, school immunization requirements ensure high coverage rates among schoolchildren. Third, a second dose of measles vaccine is needed to achieve satisfactory levels of immunity. Fourth, school immunization requirements can also ensure delivery of a second dose. Fifth, coverage assessment is crucial. Sixth, measles surveillance is critical for developing, evaluating, and refining elimination strategies. Seventh, surveillance requires laboratory backup to confirm a diagnosis. Eighth, tracking measles virus genotypes is critical to determining if an endemic strain is circulating. Ninth, once endemic transmission has been interrupted, internationally imported measles cases will continue and will cause small outbreaks. Tenth, collaborative efforts with other countries are essential to reduce imported measles cases.     

Efficacy of measles and rubella vaccination one year after the nationwide campaign in Shiraz, Iran.

BACKGROUND: The World Health Organization target for measles elimination in the Eastern Mediterranean Region was established in 2010. In Iran, the national measles-rubella campaign, targeting individuals aged 5-25 years, was initiated in December 2003. METHODS: To evaluate the impact of the campaign after one year, 909 serum samples were collected in Shiraz, southern Iran, from a population aged 6-26 years, divided into five groups according to age. IgG antibodies were tested using ELISA for the measles and rubella antibodies, and the plaque reduction neutralization test (PRNT; measles) was used for samples with equivocal results. RESULTS: Measles protective immunity reached 80.6%, 72.7%, 84.9%, and 87.5% and rubella immunity reached 91.0%, 99.6%, 99.6%, and 97.0% for the age groups 6-10, 11-15, 16-20, and 20-26 years, respectively. Seropositivity to the rubella virus in this population was high, especially in women of childbearing age (98.9%), thereby preventing congenital rubella infections. However for measles, it was significantly lower than the rate required to achieve >or=95% coverage for elimination. CONCLUSIONS: These data indicate that an increase in immunization coverage by supplementary administration of a second dose of measles vaccine is needed to interrupt the endemic transmission of the measles virus.     

The unfinished measles immunization agenda

Despite achieving and sustaining global measles vaccination coverage of about 80% over the past decade, worldwide measles remains the fifth leading cause of mortality among children aged <5 years. In May 2002, the United Nations Special Session on Children endorsed the goal of reducing measles deaths by half by 2005. Countries and World Health Organization (WHO) regions that adopted aggressive measles control or elimination strategies have shown excellent results. In 2001, countries in the Americas reported an all time low of 537 confirmed measles cases. Substantial progress in measles control has also been achieved in the WHO Western Pacific Region, in seven southern African countries, and in selected countries in WHO European, Eastern Mediterranean, and Southeast Asian regions. The ongoing measles disease burden and availability of safe and effective measles mortality reduction strategies make a compelling case to complete the unfinished agenda of measles immunization.     

Impact of the implementation of a vaccination strategy on hepatitis B virus infections in China over a 20-year period

Hepatitis B virus (HBV) vaccination has been recommended for all neonates in China since 1992. This article reviews the impact of HBV vaccination throughout the past 20 years in China. Before the introduction of the HBV vaccination program, approximately 9.8% of the general Chinese population tested positive for hepatitis B virus surface antigen (HBsAg). Since 1992, vaccination coverage has increased each year. In 1999, a National Expanded Programme on Immunization (EPI) review showed that the immunization coverage with three doses of HBV vaccine was 70.7%, and reached 99.0% in Beijing. The HBsAg carrier rate in the general population decreased to 7.2% in 2006. In particular, the prevalence of HBsAg decreased to 2.3% among children aged 5-14 years and to 1.0% among children younger than 5 years. In addition, the administration of the HBV vaccine may have reduced the risk of hepatocellular carcinoma among adults. Despite the administration of hepatitis B immunoglobulin and the HBV vaccine to children with HBsAg-positive mothers, the failure rate of HBV immunoprophylaxis was 5-10%. In China, vaccine failure was related to HBV S gene mutation and inadequate administration of HBV vaccine. The prevalence of HBV carriers in China was markedly reduced after the introduction of the universal HBV vaccination program. If we immunize all susceptible individuals with the hepatitis B vaccine (especially children), interrupt transmission, and provide antiviral treatment for existing HBV carriers, the number of new cases may be reduced to close to zero in the future and this may eventually result in the eradication of HBV.     

Measles incidence before and after mass vaccination campaigns in Burkina Faso

Burkina Faso conducted mass measles vaccination campaigns among children aged 9 months to 4 years during December 1998 and December 1999. The 1998 campaign was limited to six cities and towns, while the 1999 campaign was nationwide. The last year of explosive measles activity in Burkina Faso was 1996. Measles surveillance data suggest that the 1998 urban campaigns did not significantly impact measles incidence. After the 1999 national campaign, the total case count decreased during 2000 and 2001. However, 68% of measles cases occurred among children aged 5 years or older who were not included in the mass vaccination strategy. During 2000 and 2001, areas with high measles incidence were characterized by low population density and presence of mobile and poor populations. Measles control strategies in Sahelian Africa must balance incomplete impact on virus circulation with cost of more aggressive strategies that include older age groups.     

The challenge of achieving measles elimination in the eastern Mediterranean region by 2010

In 1997, the Eastern Mediterranean Region (EMR) of the World Health Organization adopted a resolution to eliminate measles by 2010. Of the 23 EMR member countries, 18 are polio-free and are building on this success to eliminate measles. The 5 countries where polio remains endemic are prioritizing polio eradication and working to improve measles control. Measles incidence has been reduced from 193/100,000 in 1981 to 6.8/100,000 in 2001. Supplemental vaccination campaigns for measles have been conducted since 1994 in 14 of the 18 polio-free countries. More than 50 million children have been immunized in these supplemental activities. However, in Afghanistan, Sudan, Somalia, Djibouti, and Pakistan, where 34% of the EMR population live, routine vaccination coverage for measles remains below 60% and measles deaths are estimated at 81,000 annually among children <5 years old. Significant resources must be allocated to these last 5 countries to achieve regional measles elimination by 2010.     

Measles vaccination coverage during poliomyelitis national immunization days in Burkina Faso, 1999

In 1999, Burkina Faso added measles vaccine during the second round of its poliomyelitis national immunization days (NIDs). A cluster survey was conducted in each of the country's 53 health districts to assess vaccination coverage achieved by the campaign. Forty-four percent of children aged 9-59 months had a documented prior measles vaccination, and 88% were vaccinated during NIDs. Eighty-five percent of children not previously vaccinated received measles vaccine during the campaign. Although routine vaccination coverage varied substantially among children from various socioeconomic groups, the campaign appeared to almost equally reach all groups of children surveyed. Poliovirus vaccine coverage was 90% when measles vaccine was added to the campaign, compared with 88% during the first round. In Burkina Faso, the addition of measles vaccine to poliomyelitis NIDs achieved greater equity in measles vaccination coverage according to a number of socioeconomic factors without compromising the coverage of poliovirus vaccination.     

Global measles elimination efforts: the significance of measles elimination in the United States

Lessons learned from the successful end of endemic measles virus transmission (i.e., elimination) in the United States include the critical roles of strong political commitment, a regionwide initiative, adequate funding, and a broad coalition of partners. Implications of measles elimination in the United States for global measles control and regional elimination efforts include demonstration of the high vaccination coverage and, in turn, population immunity needed for elimination; the importance of accurate monitoring of vaccination coverage at local, state, and national levels; a vaccination strategy that includes at least 2 opportunities for measles immunization; and the essential role of integrated epidemiological and laboratory surveillance. The United States, with a population of 288 million, is, to our knowledge, the largest country to have ended endemic measles transmission. This experience provides evidence that sustained interruption of transmission can be achieved in large geographic areas, suggesting the feasibility of global eradication of measles.     

Interruption of indigenous measles transmission in Bolivia since October 2000

Measles incidence in Bolivia declined after the introduction of campaign strategies in the 1980s. From 1990 to 1993, the peak incidence of measles (59 cases/100,000 population) was in 1992. In 1994, after the goal of interruption of measles transmission was adopted, a national vaccination campaign targeting children <15 years old was conducted and achieved 96% coverage. During 1995-1997, cases declined, although routine coverage was <90% in most years. During 1998-2000, a nationwide epidemic occurred among 2567 case-patients, most of whom were unvaccinated. A national vaccination campaign, with strong supervision, was conducted during November and December 1999 and targeted areas with low coverage. Only 122 cases were confirmed in 2000, with the last confirmed case occurring in October. Crucial to the control of the outbreak were sufficient resources and political support, intensive local planning, door-to-door vaccination with strict supervision, and rapid house-to-house coverage monitoring that improved accountability at the local level and timely and thorough outbreak investigations.     

Epidemiology of rubella in Finland

Before rubella vaccination programmes began, rubella infection was prevalent in Finnish children. The disease occurred as epidemics at intervals of a few years. Rubella infection was most often contracted between the ages of 2 and 12 years. Vaccinations specifically aimed at eradicating rubella were begun with monocomponent vaccine in the mid-1970s, and the measles, mumps and rubella (MMR) vaccination programme with two injections got underway in 1982. A clear reduction in rubella cases was evident a few years after the launch of the MMR programme. Owing to a sufficiently high vaccination coverage (>95% since 1987), circulation of the indigenous rubella virus in the Finnish population ceased in the late 1990s. Some rubella cases have been imported to Finland since elimination, but they have not caused any secondary cases. This shows unambiguously that protection against rubella continues to be effective, although our cohort studies imply that the vaccine induced antibody levels do decrease with time. The MMR programme has also eliminated congenital rubella syndrome (CRS) from the country. The last CRS case was recorded in 1986. As a result of the high coverage two dose MMR vaccination programme, rubella was successfully eliminated from Finland. How long the acquired protection will last remains to be seen.     

A 24-year review on the epidemiology and control of measles in Singapore, 1981-2004

The objective of our paper is to review the epidemiology of measles in Singapore and the impact of the measles vaccination program on the control of measles. Our review will form the basis for a critical appraisal of our future measles control program. We analyzed the trend of reported measles cases in relationship to measles vaccination coverage from 1981 to 2004 using routine measles notifications and measles vaccination data submitted to the Ministry of Health and the National Immunization Registry, respectively. We determined the measles vaccine efficacy using data from epidemiological investigations of reported institutional measles outbreaks. The herd immunity of the population against measles was accessed through three seroepidemiological surveys that we conducted in 1989/1990, 1993 and 1998. In addition, we collected blood specimens from every clinically diagnosed case of measles notified to the Ministry in 1998/1999 to for measles-specific IgM antibodies in order to evaluate the proportion of clinically diagnosed cases of measles that were laboratory confirmed. The incidence of measles has decreased significantly since 1981 as a result of increased vaccination coverage of 89-93% following implementation of compulsory measles vaccination in 1985. However, resurgences still occurred in 1992/1993 and 1997. With the implementation of the two-dose measles vaccination schedule, the annual number of laboratory confirmed cases of measles to date has been less than 150. Vaccine efficacy of the trivalent MMR vaccine based on institutional outbreak investigations was consistently above 92%. We also found that the overall seroprevalence of the population to measles has decreased from approximately 91.5% in 1989/1990 to 1993 to 77.9% in 1998 (mainly in children < 4 years old) and that only 7% of clinically notified cases of measles were serologically confirmed to be positive for measles. Achieving a vaccination coverage of more than 95%, tightening our MMR vaccine delivery system and strengthening surveillance of measles are essential components which must be addressed in order to interrupt measles transmission in Singapore.