Health care-associated measles outbreak in the United States after an importation: challenges and economic impact

BACKGROUND

On 12 February 2008, an infected Swiss traveler visited hospital A in Tucson, Arizona, and initiated a predominantly health care-associated measles outbreak involving 14 cases. We investigated risk factors that might have contributed to health care-associated transmission and assessed outbreak-associated hospital costs.

METHODS

Epidemiologic data were obtained by case interviews and review of medical records. Health care personnel (HCP) immunization records were reviewed to identify non-measles-immune HCP. Outbreak-associated costs were estimated from 2 hospitals.

RESULTS

Of 14 patients with confirmed cases, 7 (50%) were aged ≥ 18 years, 4 (29%) were hospitalized, 7 (50%) acquired measles in health care settings, and all (100%) were unvaccinated or had unknown vaccination status. Of the 11 patients (79%) who had accessed health care services while infectious, 1 (9%) was masked and isolated promptly after rash onset. HCP measles immunity data from 2 hospitals confirmed that 1776 (25%) of 7195 HCP lacked evidence of measles immunity. Among these HCPs, 139 (9%) of 1583 tested seronegative for measles immunoglobulin G, including 1 person who acquired measles. The 2 hospitals spent US$799,136 responding to and containing 7 cases in these facilities.

CONCLUSIONS

Suspecting measles as a diagnosis, instituting immediate airborne isolation, and ensuring rapidly retrievable measles immunity records for HCPs are paramount in preventing health care-associated spread and in minimizing hospital outbreak-response costs.

Guidance for isolation precautions for mumps in the United States: a review of the scientific basis for policy change

The 2006 mumps resurgence in the United States raised questions about the appropriate isolation period for people with mumps. To determine the scientific basis for isolation recommendations, we conducted a literature review and considered isolation of virus and virus load in saliva and respiratory secretions as factors that were related to mumps transmission risk. Although mumps virus has been isolated from 7 days before through 8 days after parotitis onset, the highest percentage of positive isolations and the highest virus loads occur closest to parotitis onset and decrease rapidly thereafter. Most transmission likely occurs before and within 5 days of parotitis onset. Transmission can occur during the prodromal phase and with subclinical infections. Updated guidance, released in 2007-2008, changed the mumps isolation period from 9 to 5 days. It is now recommended that mumps patients be isolated and standard and droplet precautions be followed for 5 days after parotitis onset.

Use of combination measles, mumps, rubella, and varicella vaccine: recommendations of the Advisory Committee on Immunization Practices (ACIP)

This report presents new recommendations adopted in June 2009 by CDC's Advisory Committee on Immunization Practices (ACIP) regarding use of the combination measles, mumps, rubella, and varicella vaccine (MMRV, ProQuad, Merck & Co., Inc.). MMRV vaccine was licensed in the United States in September 2005 and may be used instead of measles, mumps, rubella vaccine (MMR, M-M-RII, Merck & Co., Inc.) and varicella vaccine (VARIVAX, Merck & Co., Inc.) to implement the recommended 2-dose vaccine schedule for prevention of measles, mumps, rubella, and varicella among children aged 12 months-12 years. At the time of its licensure, use of MMRV vaccine was preferred for both the first and second doses over separate injections of equivalent component vaccines (MMR vaccine and varicella vaccine), which was consistent with ACIP's 2006 general recommendations on use of combination vaccines (CDC. General recommendations on immunization: recommendations of the Advisory Committee on Immunization Practices [ACIP]. MMWR 2006;55;[No. RR-15]). Since July 2007, supplies of MMRV vaccine have been temporarily unavailable as a result of manufacturing constraints unrelated to efficacy or safety. MMRV vaccine is expected to be available again in the United States in May 2010. In February 2008, on the basis of preliminary data from two studies conducted postlicensure that suggested an increased risk for febrile seizures 5-12 days after vaccination among children aged 12-23 months who had received the first dose of MMRV vaccine compared with children the same age who had received the first dose of MMR vaccine and varicella vaccine administered as separate injections at the same visit, ACIP issued updated recommendations regarding MMRV vaccine use (CDC. Update: recommendations from the Advisory Committee on Immunization Practices [ACIP] regarding administration of combination MMRV vaccine. MMWR 2008;57:258-60). These updated recommendations expressed no preference for use of MMRV vaccine over separate injections of equivalent component vaccines for both the first and second doses. The final results of the two postlicensure studies indicated that among children aged 12--23 months, one additional febrile seizure occurred 5-12 days after vaccination per 2,300-2,600 children who had received the first dose of MMRV vaccine compared with children who had received the first dose of MMR vaccine and varicella vaccine administered as separate injections at the same visit. Data from postlicensure studies do not suggest that children aged 4--6 years who received the second dose of MMRV vaccine had an increased risk for febrile seizures after vaccination compared with children the same age who received MMR vaccine and varicella vaccine administered as separate injections at the same visit. In June 2009, after consideration of the postlicensure data and other evidence, ACIP adopted new recommendations regarding use of MMRV vaccine for the first and second doses and identified a personal or family (i.e., sibling or parent) history of seizure as a precaution for use of MMRV vaccine. For the first dose of measles, mumps, rubella, and varicella vaccines at age 12--47 months, either MMR vaccine and varicella vaccine or MMRV vaccine may be used. Providers who are considering administering MMRV vaccine should discuss the benefits and risks of both vaccination options with the parents or caregivers. Unless the parent or caregiver expresses a preference for MMRV vaccine, CDC recommends that MMR vaccine and varicella vaccine should be administered for the first dose in this age group. For the second dose of measles, mumps, rubella, and varicella vaccines at any age (15 months-12 years) and for the first dose at age >or=48 months, use of MMRV vaccine generally is preferred over separate injections of its equivalent component vaccines (i.e., MMR vaccine and varicella vaccine). This recommendation is consistent with ACIP's 2009 provisional general recommendations regarding use of combination vaccines (available at http://www.cdc.gov/vaccines/recs/provisional/downloads/combo-vax-Aug2009-508.pdf), which state that use of a combination vaccine generally is preferred over its equivalent component vaccines.

Laboratory confirmation of measles in elimination settings: experience from the Republic of the Marshall Islands, 2003

OBJECTIVE

To highlight the complications involved in interpreting laboratory tests of measles immunoglobulin M (IgM) for confirmation of infection during a measles outbreak in a highly vaccinated population after conducting a mass immunization campaign as a control measure.

METHODS

This case study was undertaken in the Republic of the Marshall Islands during a measles outbreak in 2003, when response immunization was conducted. A measles case was defined as fever and rash and one or more of cough, coryza or conjunctivitis. Between 13 July and 7 November 2003, serum samples were obtained from suspected measles cases for serologic testing and nasopharyngeal swabs were taken for viral isolation by reverse transcriptase polymerase chain reaction (RT-PCR).

FINDINGS

Specimens were collected from 201 suspected measles cases (19% of total): of the ones that satisfied the clinical case definition, 45% were IgM positive (IgM+) and, of these, 24% had received measles vaccination within the previous 45 days (up to 45 days after vaccination an IgM+ result could be due to either vaccination or wild-type measles infection). The proportion of IgM+ results varied with clinical presentation, the timing of specimen collection and vaccination status. Positive results on RT-PCR occurred in specimens from eight IgM-negative and four IgM+ individuals who had recently been vaccinated.

CONCLUSION

During measles outbreaks, limiting IgM testing to individuals who meet the clinical case definition and have not been recently vaccinated allows for measles to be confirmed while conserving resources.

Mumps epidemiology and immunity: the anatomy of a modern epidemic

The success of the measles, mumps, and rubella 2-dose vaccination program led public health officials in 1998 to set a goal to eliminate endemic transmission of mumps virus by 2010 in the United States. The large outbreak of mumps in the spring of 2006 has led public health officials to re-evaluate this goal and to recognize that the transmission and epidemiology of mumps in highly vaccinated populations may be different than anticipated. During 2006, a total of 6584 confirmed and probable cases of mumps were reported to the Centers for Disease Control and Prevention and most of these, 5865, occurred between January 1 and July 31. The peak of the outbreak was in April and seemed to be focused on college campuses in 9 midwestern states with Iowa having the highest attack rate. College campuses with mumps outbreaks included ones with 77% to 97% of students having had 2 doses of a mumps vaccine. Diagnosing mumps proved to be problematic in vaccinated persons (ie, laboratory tests seemed to be insensitive and some apparent mumps cases had mild nonclassic illness). The outbreak demonstrated that mumps can sometimes transmit efficiently in highly vaccinated populations and the clinical and laboratory diagnosis of mumps in vaccinated persons is more difficult than in naive persons. The reason for this mumps outbreak is not clear but probably results from multiple factors contributing to an overall increase in susceptibility and/or transmission.

Varicella prevention in the United States: a review of successes and challenges

OBJECTIVE

In 1995, the United States was the first country to introduce a universal 1-dose childhood varicella vaccination program. In 2006, the US varicella vaccine policy was changed to a routine 2-dose childhood program, with catchup vaccination for older children. The objective of this review was to summarize the US experience with the 1-dose varicella vaccination program, present the evidence considered for the policy change, and outline future challenges of the program.

METHODS

We conducted a review of publications identified by searching PubMed for the terms "varicella," "varicella vaccine," and "herpes zoster." The search was limited to US publications except for herpes zoster; we reviewed all published literature on herpes zoster incidence.

RESULTS

A single dose of varicella vaccine was 80% to 85% effective in preventing disease of any severity and >95% effective in preventing severe varicella and had an excellent safety profile. The vaccination program reduced disease incidence by 57% to 90%, hospitalizations by 75% to 88%, deaths by >74%, and direct inpatient and outpatient medical expenditures by 74%. The decline of cases plateaued between 2003 and 2006, and outbreaks continued to occur, even among highly vaccinated school populations. Compared with children who received 1 dose, in 1 clinical trial, 2-dose vaccine recipients developed in a larger proportion antibody titers that were more likely to protect against breakthrough disease and had a 3.3-fold lower risk for breakthrough disease and higher vaccine efficacy. Two studies showed no increase in overall herpes zoster incidence, whereas 2 others showed an increase.

CONCLUSIONS

A decade of varicella prevention in the United States has resulted in a dramatic decline in disease; however, even with high vaccination coverage, the effectiveness of 1 dose of vaccine did not generate sufficient population immunity to prevent community transmission. A 2-dose varicella vaccine schedule, therefore, was recommended for children in 2006. Data are inconclusive regarding an effect of the varicella vaccination program on herpes zoster epidemiology.

Prevention of herpes zoster: recommendations of the Advisory Committee on Immunization Practices (ACIP)

These recommendations represent the first statement by the Advisory Committee on Immunization Practices (ACIP) on the use of a live attenuated vaccine for the prevention of herpes zoster (zoster) (i.e., shingles) and its sequelae, which was licensed by the U.S. Food and Drug Administration (FDA) on May 25, 2006. This report summarizes the epidemiology of zoster and its sequelae, describes the zoster vaccine, and provides recommendations for its use among adults aged > or =60 years in the United States. Zoster is a localized, generally painful cutaneous eruption that occurs most frequently among older adults and immunocompromised persons. It is caused by reactivation of latent varicella zoster virus (VZV) decades after initial VZV infection is established. Approximately one in three persons will develop zoster during their lifetime, resulting in an estimated 1 million episodes in the United States annually. A common complication of zoster is postherpetic neuralgia (PHN), a chronic, often debilitating pain condition that can last months or even years. The risk for PHN in patients with zoster is 10%-18%. Another complication of zoster is eye involvement, which occurs in 10%-25% of zoster episodes and can result in prolonged or permanent pain, facial scarring, and loss of vision. Approximately 3% of patients with zoster are hospitalized; many of these episodes involved persons with one or more immunocompromising conditions. Deaths attributable to zoster are uncommon among persons who are not immunocompromised. Prompt treatment with the oral antiviral agents acyclovir, valacyclovir, and famciclovir decreases the severity and duration of acute pain from zoster. Additional pain control can be achieved in certain patients by supplementing antiviral agents with corticosteroids and with analgesics. Established PHN can be managed in certain patients with analgesics, tricyclic antidepressants, and other agents. Licensed zoster vaccine is a lyophilized preparation of a live, attenuated strain of VZV, the same strain used in the varicella vaccines. However, its minimum potency is at least 14-times the potency of single-antigen varicella vaccine. In a large clinical trial, zoster vaccine was partially efficacious at preventing zoster. It also was partially efficacious at reducing the severity and duration of pain and at preventing PHN among those developing zoster. Zoster vaccine is recommended for all persons aged > or =60 years who have no contraindications, including persons who report a previous episode of zoster or who have chronic medical conditions. The vaccine should be offered at the patient's first clinical encounter with his or her health-care provider. It is administered as a single 0.65 mL dose subcutaneously in the deltoid region of the arm. A booster dose is not licensed for the vaccine. Zoster vaccination is not indicated to treat acute zoster, to prevent persons with acute zoster from developing PHN, or to treat ongoing PHN. Before administration of zoster vaccine, patients do not need to be asked about their history of varicella (chickenpox) or to have serologic testing conducted to determine varicella immunity.

The impact of the varicella vaccination program on herpes zoster epidemiology in the United States: a review

Speculation that a universal varicella vaccination program might lead to an increase in herpes zoster (HZ) incidence has been supported by modeling studies that assume that exposure to varicella boosts immunity and protects against reactivation of varicella-zoster virus (VZV) as HZ. Such studies predict an increase in HZ incidence until the adult population becomes predominantly composed of individuals with vaccine-induced immunity who do not harbor wild-type VZV. In the United States, a varicella vaccination program was implemented in 1995. Since then, studies monitoring HZ incidence have shown inconsistent findings: 2 studies have shown no increase in overall incidence, whereas 1 study has shown an increase. Studies from Canada and the United Kingdom have shown increasing rates of HZ incidence in the absence of a varicella vaccination program. Data suggest that heretofore unidentified risk factors for HZ also are changing over time. Further studies are needed to identify these factors, to isolate possible additional effects from a varicella vaccination program. Untangling the contribution of these different factors on HZ epidemiology will be challenging.

Varicella among adults: data from an active surveillance project, 1995-2005

We report detailed population-based data on varicella among adults. In 2 US varicella active surveillance sites with high vaccine coverage among young children, the incidence of varicella among adults declined 74% during 1995-2005. A low proportion (3%) of adults with varicella had been vaccinated, with no improvement over the decade of program implementation, suggesting that the decline was likely secondary to herd-immunity effects. Compared with children, adults had more severe varicella in terms of both clinical presentation and frequency of complications. However, <30% of adults with varicella were treated with acyclovir. Among adolescents, illness severity was intermediate between that in children and adults. Varicella cases are preventable through vaccination. As we enter the second decade of the varicella vaccination program in the United States, we need to ensure that susceptible adolescents and adults are adequately protected from varicella by vaccination and that those who acquire varicella are appropriately treated with effective antiviral treatment.

Varicella disease among vaccinated persons: clinical and epidemiological characteristics, 1997-2005

Approximately 1 in every 5 children who receives 1 dose of varicella vaccine may develop varicella disease, also known as breakthrough disease, if exposed to varicella-zoster virus. Currently, in communities with high vaccination coverage, varicella cases mostly occur in vaccinated individuals. We report on the first population-based description of the clinical and epidemiological characteristics of varicella in populations with increasing vaccine coverage between 1997 and 2005. In vaccinated children 1-14 years of age, varicella was most often mild and modified; the atypical disease presentation may result in diagnostic challenges to health care providers. However, despite the generally mild nature of these cases, approximately 25% caused >50 lesions, and some resulted in serious complications similar to those occurring in unvaccinated individuals. Continued surveillance of the risk and characteristics of breakthrough disease will be needed, to monitor the effect of the new 2-dose vaccine recommendation for children.

Changing varicella epidemiology in active surveillance sites--United States, 1995-2005

Significant reductions in varicella incidence were reported from 1995 to 2000 in the varicella active surveillance sites of Antelope Valley (AV), California, and West Philadelphia (WP), Pennsylvania. We examined incidence rates, median age, and vaccination status of case patients for 1995-2005. Coverage data were from the National Immunization Survey. By 2005, coverage among children 19-35 months of age reached 92% (AV) and 94% (WP); 57% and 64% of case patients in AV and WP, respectively, were vaccinated; and varicella incidence declined by 89.8% in AV and 90.4% in WP. Incidence declined in all age groups, especially among children <10 years of age in both sites and among adolescents 10-14 years of age in WP. In AV, since 2000, the incidence among adolescents 10-14 and 15-19 years of age increased. Implementation of school requirements through 10th grade in WP may explain the differences in the decline in incidence among adolescents. Continued surveillance will be important to monitor the impact that the 2-dose vaccine policy in children has on varicella epidemiology.

Varicella vaccine exposure during pregnancy: data from 10 Years of the pregnancy registry

BACKGROUND

The Pregnancy Registry for Varivax (Merck) was established to monitor for congenital varicella syndrome or other birth defects in the offspring of women who were exposed to varicella vaccine while pregnant.

METHODS

The registry receives voluntary reports from health care providers or consumers about women given the vaccine 3 months before or during pregnancy. Follow-up is conducted to obtain and classify pregnancy outcomes. All reports are evaluated for the presence of birth defects. Outcomes from prospectively reported pregnancy exposures are used to calculate rates and 95% confidence intervals.

RESULTS

From 17 March 1995 through 16 March 2005, 981 women were enrolled. Pregnancy outcomes were available for 629 prospectively enrolled women. Among the 131 live births to varicella-zoster virus-seronegative women, there was no evidence of congenital varicella syndrome (rate, 0% [95% confidence interval [CI], 0%-6.7%]), and major birth defects were observed in 3 infants (rate, 3.7% [95% CI, 0.8%-10.7%]).

CONCLUSIONS

Although the numbers of exposures are not sufficient to rule out a very low risk, data collected in the pregnancy registry to date do not support a relationship between the occurrence of congenital varicella syndrome or other birth defects and varicella vaccine exposure during pregnancy.

Laboratory diagnosis and characteristics of breakthrough varicella in children

The atypical features of varicella in vaccinated persons (breakthrough varicella [BTV]) present diagnostic challenges. We examined varicella-zoster virus (VZV) polymerase chain reaction (PCR) and immunoglobulin (Ig) M and IgG serologic test results for confirming BTV cases. Among 33 vaccinated children with varicella-like rash, we identified wild-type VZV in 58% overall and in 76% of those with adequate tissue specimens; no vaccine-type virus was found. Of the 12 subjects with PCR-confirmed BTV and acute-phase serum samples, 9 had detectable IgM, and all had highly elevated acute-phase IgG titers. Six subjects with negative PCR results had lower IgG titers and negative IgM results. Although PCR is the preferred method for laboratory confirmation of BTV, a positive serum varicella IgM test result should also be considered to be diagnostic in a suspected BTV case; however, a negative IgM test result cannot be used to rule out the diagnosis. The value of highly elevated IgG titers needs further evaluation. Larger studies are needed to confirm these results.

Status of school entry requirements for varicella vaccination and vaccination coverage 11 years after implementation of the varicella vaccination program

We reviewed progress toward adoption of day care and school entry requirements in each state and the District of Columbia (DC) and compared varicella vaccination coverage by state to year of implementation of day care entry requirements. By the start of the 2006-2007 school year, 46 states (92%) and DC had implemented entry requirements for varicella vaccination. Between 1997 and 2005, national varicella vaccination coverage among children 19-35 months of age increased from 25.8% to 87.9%. Implementation of day care entry requirements in 2000 or earlier was associated with higher vaccination coverage (> or =90%; P=.002). Implementation of day care and school entry requirements for varicella vaccination is an important strategy for achieving and maintaining high vaccination coverage among preschool- and school-aged children in the United States. The newly adopted vaccine policy recommendation of 2 doses of varicella vaccine for all school-aged children should be incorporated into the states' school entry requirements.

Safety of varicella vaccine after licensure in the United States: experience from reports to the vaccine adverse event reporting system, 1995-2005

Widespread use of varicella vaccine in the United States could enable detection of rare adverse events not identified previously. We reviewed data from 1995 to 2005 from the Vaccine Adverse Event Reporting System, including data from laboratory analyses, to distinguish adverse events associated with wild-type varicella-zoster virus (VZV) versus those associated with vaccine strain. Almost 48 million doses of varicella vaccine were distributed between 1995 and 2005. There were 25,306 adverse events reported (52.7/100,000 doses distributed); 5.0% were classified as serious (2.6/100,000 doses distributed). Adverse events associated with evidence of vaccine-strain VZV included meningitis in patients with concurrent herpes zoster. Patients with genetic predispositions may rarely have disease triggered by receipt of varicella vaccine. Overall, serious adverse events reported after varicella vaccination continue to be rare and must be considered relative to the substantial benefits of varicella vaccination. Ongoing safety surveillance and further studies may shed light on some of the hypothesized associations.

An economic analysis of the universal varicella vaccination program in the United States

Frequent varicella outbreaks with sizable impact on the US public health system have continued to occur despite the success of the country's 1-dose varicella vaccination program. The Advisory Committee on Immunization Practices recently recommended adding a routine second dose of varicella vaccine and weighed economic projections as well as public health goals in their deliberations. This decision-tree-based analysis was conducted to evaluate the economic impact of the projected 2-dose varicella vaccination program as well as the existing 1-dose program. The analysis used population-based vaccination coverage and disease incidence data to make projections for a hypothetical US birth cohort of 4,100,000 infants born in 2006. Compared with no vaccination, both the 1-dose program (societal benefit-cost ratio [BCR], 4.37) and 2-dose program (BCR, 2.73) were estimated to be cost saving from the societal perspective. Compared with the 1-dose program, the incremental second dose was not cost saving (societal incremental BCR, 0.56). The incremental cost-effectiveness ratio for the second dose was $343 per case prevented, or approximately $109,000 per quality-adjusted life-year saved, and these results were sensitive to assumptions about vaccine effectiveness and prices.

Varicella vaccine effectiveness in the US vaccination program: a review

Varicella vaccine (Varivax, Merck) has been available in the United States since 1995. We reviewed published results of postlicensure studies of vaccine effectiveness. Among 19 studies, 17 reported on the effectiveness of vaccine received before exposure, and 2 reported on effectiveness after exposure. Studies used retrospective and prospective cohort, case-control, and secondary attack rate (household contact) designs. The majority of estimates assessed protection against clinically diagnosed varicella. One dose of varicella vaccine was 84.5% effective (median; range, 44%-100%) in preventing all varicella and 100% effective (mean and median) in preventing severe varicella. When administered after exposure, varicella vaccine was highly effective in preventing or modifying varicella. Although 1 dose of varicella vaccine has provided excellent protection, a higher degree of effectiveness is needed in order to interrupt transmission and to prevent outbreaks in settings with high contact rates. Monitoring the effectiveness of the newly recommended 2-dose childhood vaccine schedule for varicella vaccine is a priority.

Recent resurgence of mumps in the United States

BACKGROUND

The widespread use of a second dose of mumps vaccine among U.S. schoolchildren beginning in 1990 was followed by historically low reports of mumps cases. A 2010 elimination goal was established, but in 2006 the largest mumps outbreak in two decades occurred in the United States.

METHODS

We examined national data on mumps cases reported during 2006, detailed case data from the most highly affected states, and vaccination-coverage data from three nationwide surveys.

RESULTS

A total of 6584 cases of mumps were reported in 2006, with 76% occurring between March and May. There were 85 hospitalizations, but no deaths were reported; 85% of patients lived in eight contiguous midwestern states. The national incidence of mumps was 2.2 per 100,000, with the highest incidence among persons 18 to 24 years of age (an incidence 3.7 times that of all other age groups combined). In a subgroup analysis, 83% of these patients reported current college attendance. Among patients in eight highly affected states with known vaccination status, 63% overall and 84% between the ages of 18 and 24 years had received two doses of mumps vaccine. For the 12 years preceding the outbreak, national coverage of one-dose mumps vaccination among preschoolers was 89% or more nationwide and 86% or more in highly affected states. In 2006, the national two-dose coverage among adolescents was 87%, the highest in U.S. history.

CONCLUSIONS

Despite a high coverage rate with two doses of mumps-containing vaccine, a large mumps outbreak occurred, characterized by two-dose vaccine failure, particularly among midwestern college-age adults who probably received the second dose as schoolchildren. A more effective mumps vaccine or changes in vaccine policy may be needed to avert future outbreaks and achieve the elimination of mumps.

An evaluation of infant immunization in Africa: is a transformation in progress?

OBJECTIVE

To assess the progress made towards meeting the goals of the African Regional Strategic Plan of the Expanded Programme on Immunization between 2001 and 2005.

METHODS

We reviewed data from national infant immunization programmes in the 46 countries of WHOs African Region, reviewed the literature and analysed existing data sources. We carried out face-to-face and telephone interviews with relevant staff members at regional and subregional levels.

FINDINGS

The African Region fell short of the target for 80% of countries to achieve at least 80% immunization coverage by 2005. However, diphtheria-tetanus-pertussis-3 coverage increased by 15%, from 54% in 2000 to 69% in 2004. As a result, we estimate that the number of nonimmunized children declined from 1.4 million in 2002 to 900,000 in 2004. In 2004, four of seven countries with endemic or re-established wild polio virus had coverage of 50% or less, and some neighbouring countries at high risk of importation did not meet the 80% vaccination target. Reported measles cases dropped from 520,000 in 2000 to 316,000 in 2005, and mortality was reduced by approximately 60% when compared to 1999 baseline levels. A network of measles and yellow fever laboratories had been established in 29 countries by July 2005.

CONCLUSION

Rates of immunization coverage are improving dramatically in the WHO African Region. The huge increases in spending on immunization and the related improvements in programme performance are linked predominantly to increases in donor funding.