The past, present, and future of immunization in the Americas

The Pan American Journal of Public Health recognizes with appreciation the contributions of the members of the Editorial Committee, and authors of the Overview article. Their contributions and dedication to this issue on immunization in the Region of the Americas were extraordinary and helped make the manuscripts more interesting, more accurate, and more useful to our readers and all others who work to improve the health of the peoples of the Americas. The Journal would like to give special thanks to the General Coordination of the National Immunization Program, Department of Transmissible Disease Surveillance, Health Surveillance Secretariat, Ministry of Health, Brazil, whose financial and programmatic contributions were essential to the publication of this special issue.

Expansion of Vaccination Services and Strengthening Vaccine-Preventable Diseases Surveillance in Haiti, 2010-2016.

Following the 2010 earthquake, Haiti was at heightened risk for vaccine-preventable diseases (VPDs) outbreaks due to the exacerbation of long-standing gaps in the vaccination program and subsequent risk of VPD importation from other countries. Therefore, partners supported the Haitian Ministry of Health and Population to improve vaccination services and VPD surveillance. During 2010-2016, three polio, measles, and rubella vaccination campaigns were implemented, achieving a coverage > 90% among children and maintaining Haiti free of those VPDs. Furthermore, Haiti is on course to eliminate maternal and neonatal tetanus, with 70% of communes achieving tetanus vaccine two-dose coverage > 80% among women of childbearing age. In addition, the vaccine cold chain storage capacity increased by 91% at the central level and 285% at the department level, enabling the introduction of three new vaccines (pentavalent, rotavirus, and pneumococcal conjugate vaccines) that could prevent an estimated 5,227 deaths annually. Haiti moved from the fourth worst performing country in the Americas in 2012 to the sixth best performing country in 2015 for adequate investigation of suspected measles/rubella cases. Sentinel surveillance sites for rotavirus diarrhea and meningococcal meningitis were established to estimate baseline rates of those diseases prior to vaccine introduction and to evaluate the impact of vaccination in the future. In conclusion, Haiti significantly improved vaccination services and VPD surveillance. However, high dependence on external funding and competing vaccination program priorities are potential threats to sustaining the improvements achieved thus far. Political commitment and favorable economic and legal environments are needed to maintain these gains.

Polio Endgame: Lessons Learned From the Immunization Systems Management Group.

The Immunization Systems Management Group (IMG) was established to coordinate and oversee objective 2 of the Polio Eradication and Endgame Strategic Plan 2013-2018, namely, (1) introduction of ≥1 dose of inactivated poliovirus vaccine in all 126 countries using oral poliovirus vaccine (OPV) only as of 2012, (2) full withdrawal of OPV, starting with the withdrawal of its type 2 component, and (3) using polio assets to strengthen immunization systems in 10 priority countries. The IMG's inclusive, transparent, and partnership-focused approach proved an effective means of leveraging the comparative and complementary strengths of each IMG member agency. This article outlines 10 key factors behind the IMG's success, providing a potential set of guiding principles for the establishment and implementation of other interagency collaborations and initiatives beyond the polio sphere.

Root Causes of Poor Immunisation Data Quality and Proven Interventions: A Systematic Literature Review.

Introduction: Effective allocation of resources and investments heavily rely on good quality data. As global investments in vaccines increases, particularly by organisations such as Gavi, The Vaccine Alliance, Switzerland, the demand for data which is accurate and representative is urgent. Understanding what causes poor immunisation data and how to address these problems are therefore key in maximizing investments, improving coverage and reducing risks of outbreaks. Objective: Identify the root causes of poor immunisation data quality and proven solutions for guiding future data quality interventions. Methods and Results: Qualitative systematic review of both scientific and grey literature using key words on immunisation and health information systems. Once screened, articles were classified either as identifying root causes of poor data quality or as an intervention to improve data quality. A total of 8,646 articles were initially identified which were screened and reduced to 26. Results were heterogeneous in methodology, settings and conclusions with a variation of outcomes. Key themes were underperformance in health facilities and limited Human Resource (HR) capacity at the peripheral level leading to data of poor quality. Repeated reference to a "culture" of poor data collection, reporting and use in low-income countries was found implying that it is the attitudes and subsequent behaviour of staff that prevents good quality data. Documented interventions mainly involved implementing Information Communication Technology (ICT) at the district level. However, without changes in HR capacity the skills and practices of staff remain a key impediment to reaching its full impact. Discussion: There was a clear incompatibility between identified root causes, mainly being behavioural and organizational factors, and interventions introducing predominantly technical factors. More emphasis should be placed on interventions that build on current practices and skills in a gradual process in order to be more readily adopted by health workers. Major gaps in the literature exist mainly in the lack of assessment at central and intermediate levels and association between inaccurate target setting from outdated census data and poor data quality as well as limited documentation of interventions that target behaviour change and policy change. This prevents the ability to make informed decisions on best methodology for improving data quality.

Vaccination Coverage Among Children Aged 19-35 Months - United States, 2015.

Sustained high coverage with recommended vaccinations among children has kept many vaccine-preventable diseases at low levels in the United States (1). To assess coverage with vaccinations recommended for children by age 2 years in the United States (2), CDC analyzed data collected by the 2015 National Immunization Survey (NIS) for children aged 19-35 months (born January 2012-May 2014). Overall, coverage did not change during 2014-2015. Coverage in 2015 was highest for ≥3 doses of poliovirus vaccine (93.7%), ≥3 doses of hepatitis B vaccine (HepB) (92.6%), ≥1 dose of measles, mumps, and rubella vaccine (MMR) (91.9%), and ≥1 dose of varicella vaccine (91.8%). The data were also examined for potential vaccination coverage differences by race/ethnicity, poverty status, and urbanicity. Although disparities were noted for each of these factors, the most striking differences were seen for poverty status. Children living below the federal poverty level* had lower coverage with most of the vaccinations assessed compared with children living at or above the poverty level; the largest disparities were for rotavirus vaccine (66.8% versus 76.8%), ≥4 doses of pneumococcal conjugate vaccine (PCV) (78.9% versus 87.2%), the full series of Haemophilus influenzae type b vaccine (Hib) (78.1% versus 85.5%), and ≥4 doses of diphtheria, tetanus, and acellular pertussis vaccine (DTaP) (80.2% versus 87.1%). Although coverage was high in some groups, opportunities exist to continue to address disparities. Implementation of evidence-based interventions, including strategies to enhance access to vaccination services and systems strategies that can reduce missed opportunities, has the potential to increase vaccination coverage for children living below the poverty level and in rural areas (3).

Vaccination Coverage Among Children in Kindergarten - United States, 2015-16 School Year.

State-mandated vaccination requirements for school entry protect children and communities against vaccine-preventable diseases (1). Each school year, federally funded immunization programs (e.g., states, territories, jurisdictions) collect and report kindergarten vaccination data to CDC. This report describes vaccination coverage estimates in all 50 states and the District of Columbia (DC), and the estimated number of kindergartners with at least one vaccine exemption in 47 states and DC, during the 2015-16 school year. Median vaccination coverage* was 94.6% for 2 doses of measles, mumps and rubella vaccine (MMR); 94.2% for diphtheria, tetanus, and acellular pertussis vaccine (DTaP); and 94.3% for 2 doses of varicella vaccine. MMR coverage increased in 32 states during the last year, and 22 states reported coverage ≥95% (2). A total of 45 states and DC had either a grace period allowing students to attend school before providing documentation of vaccination or provisional enrollment that allows undervaccinated students to attend school while completing a catch-up schedule. Among the 23 states that were able to voluntarily report state-level data on grace period or provisional enrollment to CDC, a median of 2.0% of kindergartners were not documented as completely vaccinated and were attending school within a grace period or were provisionally enrolled. The median percentage of kindergartners with an exemption from one or more vaccinations† was 1.9%. State and local immunization programs, in cooperation with schools, can improve vaccination coverage by ensuring that all kindergartners are vaccinated during the grace period or provisional enrollment.

Assessing strategies for increasing urban routine immunization coverage of childhood vaccines in low and middle-income countries: A systematic review of peer-reviewed literature.

INTRODUCTION: Immunization programs in developing countries increasingly face challenges to ensure equitable delivery of services within cities where rapid urban growth can result in informal settlements, poor living conditions, and heterogeneous populations. A number of strategies have been utilized in developing countries to ensure high community demand and equitable availability of urban immunization services; however, a synthesis of the literature on these strategies has not previously been undertaken. METHODS: We reviewed articles published in English in peer-reviewed journals between 1990 and 2013 that assessed interventions for improving routine immunization coverage in urban areas in low- and middle-income countries. We categorized the intervention in each study into one of three groups: (1) interventions aiming to increase utilization of immunization services; (2) interventions aiming to improve availability of immunization services by healthcare providers, or (3) combined availability and utilization interventions. We summarized the main quantitative outcomes from each study and effective practices from each intervention category. RESULTS: Fifteen studies were identified; 87% from the African, Eastern Mediterranean and Southeast Asian regions of the World Health Organization (WHO). Six studies were randomized controlled trials, eight were pre- and post-intervention evaluations, and one was a cross-sectional study. Four described interventions designed to improve availability of routine immunization services, six studies described interventions that aimed to increase utilization, and five studies aiming to improve both availability and utilization of services. All studies reported positive change in their primary outcome indicator, although seven different primary outcomes indicators were used across studies. Studies varied considerably with respect to the type of intervention assessed, study design, and length of intervention assessment. CONCLUSION: Few studies have assessed interventions designed explicitly for the unique challenges facing immunization programs in urban areas. Further research on sustainability, scalability, and cost-effectiveness of interventions is needed to fill this gap.

Knowledge, Attitudes, and Practices regarding Diarrhea and Cholera following an Oral Cholera Vaccination Campaign in the Solomon Islands.

BACKGROUND: In response to a 2011 cholera outbreak in Papua New Guinea, the Government of the Solomon Islands initiated a cholera prevention program which included cholera disease prevention and treatment messaging, community meetings, and a pre-emptive cholera vaccination campaign targeting 11,000 children aged 1-15 years in selected communities in Choiseul and Western Provinces. METHODOLOGY AND PRINCIPAL FINDINGS: We conducted a post-vaccination campaign, household-level survey about knowledge, attitudes, and practices regarding diarrhea and cholera in areas targeted and not targeted for cholera vaccination. Respondents in vaccinated areas were more likely to have received cholera education in the previous 6 months (33% v. 9%; p = 0.04), to know signs and symptoms (64% vs. 22%; p = 0.02) and treatment (96% vs. 50%; p = 0.02) of cholera, and to be aware of cholera vaccine (48% vs. 14%; p = 0.02). There were no differences in water, sanitation, and hygiene practices. CONCLUSIONS: This pre-emptive OCV campaign in a cholera-naïve community provided a unique opportunity to assess household-level knowledge, attitudes, and practices regarding diarrhea, cholera, and water, sanitation, and hygiene (WASH). Our findings suggest that education provided during the vaccination campaign may have reinforced earlier mass messaging about cholera and diarrheal disease in vaccinated communities.

Vaccination Coverage Among Children in Kindergarten - United States, 2014-15 School Year.

State and local jurisdictions require children to be vaccinated before starting school to maintain high vaccination coverage and protect schoolchildren from vaccine-preventable diseases. State vaccination requirements, which include school vaccination and exemption laws and health department regulations, permit medical exemptions for students with a medical contraindication to receiving a vaccine or vaccine component and may allow nonmedical exemptions for religious reasons or philosophic beliefs. To monitor state and national vaccination coverage and exemption levels among children attending kindergarten, CDC analyzes school vaccination data collected by federally funded state, local, and territorial immunization programs. This report describes vaccination coverage estimates in 49 states and the District of Columbia (DC) and vaccination exemption estimates in 46 states and DC that reported the number of children with at least one exemption among kindergartners during the 2014-15 school year. Median vaccination coverage* was 94.0% for 2 doses of measles, mumps, and rubella (MMR) vaccine; 94.2% for the local requirements for diphtheria, tetanus, and acellular pertussis vaccine (DTaP); and 93.6% for 2 doses of varicella vaccine among the 39 states and DC with a 2-dose requirement. The median percentage of any exemptions† was 1.7%. Although statewide vaccination coverage among kindergartners was high during the 2014-15 school year, geographic pockets of low vaccination coverage and high exemption levels can place children at risk for vaccine-preventable diseases. Appropriate school vaccination coverage assessments can help immunization programs identify clusters of low coverage and develop partnerships with schools and communities to ensure that children are protected from vaccine-preventable diseases.

Lessons learned from the development of a new methodology to assess missed opportunities for vaccination in Latin America and the Caribbean.

The Pan American Health Organization recently developed a practical guide for evaluating missed opportunities for vaccination among children aged <5 years. A missed opportunity occurs when an individual eligible for vaccination has contact with a health facility and does not receive a needed vaccine, despite having no contraindications. In this article, we discuss the strengths and limitations of this new methodology and present lessons learned from recent studies on undervaccination in Latin America. Our findings should be useful to countries embarking on assessing the magnitude and the causes of missed opportunities for vaccination children experience at health facilities.

The development of global vaccine stockpiles.

Global vaccine stockpiles, in which vaccines are reserved for use when needed for emergencies or supply shortages, have effectively provided countries with the capacity for rapid response to emergency situations, such as outbreaks of yellow fever and meningococcal meningitis. The high cost and insufficient supply of many vaccines, including oral cholera vaccine and pandemic influenza vaccine, have prompted discussion on expansion of the use of vaccine stockpiles to address a wider range of emerging and re-emerging diseases. However, the decision to establish and maintain a vaccine stockpile is complex and must take account of disease and vaccine characteristics, stockpile management, funding, and ethical concerns, such as equity. Past experience with global vaccine stockpiles provide valuable information about the processes for their establishment and maintenance. In this Review we explored existing literature and stockpile data to discuss the lessons learned and to inform the development of future vaccine stockpiles.

Expansion of syndromic vaccine preventable disease surveillance to include bacterial meningitis and Japanese encephalitis: evaluation of adapting polio and measles laboratory networks in Bangladesh, China and India, 2007-2008.

BACKGROUND: Surveillance for acute flaccid paralysis with laboratory confirmation has been a key strategy in the global polio eradication initiative, and the laboratory platform established for polio testing has been expanded in many countries to include surveillance for cases of febrile rash illness to identify measles and rubella cases. Vaccine-preventable disease surveillance is essential to detect outbreaks, define disease burden, guide vaccination strategies and assess immunization impact. Vaccines now exist to prevent Japanese encephalitis (JE) and some etiologies of bacterial meningitis. METHODS: We evaluated the feasibility of expanding polio-measles surveillance and laboratory networks to detect bacterial meningitis and JE, using surveillance for acute meningitis-encephalitis syndrome in Bangladesh and China and acute encephalitis syndrome in India. We developed nine syndromic surveillance performance indicators based on international surveillance guidelines and calculated scores using supervisory visit reports, annual reports, and case-based surveillance data. RESULTS: Scores, variable by country and targeted disease, were highest for the presence of national guidelines, sustainability, training, availability of JE laboratory resources, and effectiveness of using polio-measles networks for JE surveillance. Scores for effectiveness of building on polio-measles networks for bacterial meningitis surveillance and specimen referral were the lowest, because of differences in specimens and techniques. CONCLUSIONS: Polio-measles surveillance and laboratory networks provided useful infrastructure for establishing syndromic surveillance and building capacity for JE diagnosis, but were less applicable for bacterial meningitis. Laboratory-supported surveillance for vaccine-preventable bacterial diseases will require substantial technical and financial support to enhance local diagnostic capacity.

Strengthening the partnership between routine immunization and the global polio eradication initiative to achieve eradication and assure sustainability.

Since the launch of the Global Polio Eradication Initiative (GPEI) in 1988, the number of polio endemic countries has declined from 125 to 3 in 2013. Despite this remarkable achievement, ongoing circulation of wild poliovirus in polio-endemic countries and the increase in the number of circulating vaccine-derived poliovirus cases, especially those caused by type 2, is a cause for concern. The Polio Eradication and Endgame Strategic Plan 2013-2018 (PEESP) was developed and includes 4 objectives: detection and interruption of poliovirus transmission, containment and certification, legacy planning, and a renewed emphasis on strengthening routine immunization (RI) programs. This is critical for the phased withdrawal of oral poliovirus vaccine, beginning with the type 2 component, and the introduction of a single dose of inactivated polio vaccine into RI programs. This objective has inspired renewed consideration of how the GPEI and RI programs can mutually benefit one another, how the infrastructure from the GPEI can be used to strengthen RI, and how a strengthened RI can facilitate polio eradication. The PEESP is the first GPEI strategic plan that places strong and clear emphasis on the necessity of improving RI to achieve and sustain global polio eradication.

Overview of global, regional, and national routine vaccination coverage trends and growth patterns from 1980 to 2009: implications for vaccine-preventable disease eradication and elimination initiatives.

BACKGROUND: Review of the historical growth in annual vaccination coverage across countries and regions can better inform decision makers' development of future goals and strategies to improve routine vaccination services. METHODS: Using the World Health Organization (WHO) and the United Nations Children's Fund estimates of annual national third dose of diphtheria-tetanus-pertussis-containing vaccine (DTP3) and third dose of polio vaccine (POL3) coverage for 1980-2009, we calculated the mean absolute annual rate of change in national DTP3 coverage among all countries (globally) and among countries within each WHO region, as well as the number of years taken by each region to reach specific regional coverage levels. Last, we assessed differences in mean absolute annual rate of change in DTP3 coverage, stratified by baseline level of DTP3 coverage. RESULTS: During the 1980s, global DTP3 coverage increased a mean of 5.3 percentage points/year. Annual rate of change decreased to 0.5 percentage points/year in the 1990s and then increased to 0.9 percentage points/year during the 2000s. Mean annual rate of change in coverage across all countries was highest (9.2 percentage points) when national coverage levels were 26%-30% and lowest (-0.9 percentage points) when national coverage levels were 96%-100%. Regional differences existed as both WHO South-East Asia Region and WHO African Region countries experienced mean negative DTP3 coverage growth at lower coverage levels (81%-85%) than other regions. The regions that have achieved 95% DTP3 coverage (Americas, Western Pacific, and European) took 25-29 years to reach that level from a level of 50% DTP3 coverage. POL3 coverage change trends were similar to described DTP3 coverage change trends. CONCLUSIONS: Mean national coverage growth patterns across all regions are nonlinear as coverage levels increase. Saturation points of mean 0 percentage-point growth in annual coverage varies by region and require further investigation. The achievement of >90% routine coverage is observed to take decades, which has implications for disease eradication and elimination initiatives.

Issues and considerations in the use of serologic biomarkers for classifying vaccination history in household surveys.

Accurate estimates of vaccination coverage are crucial for assessing routine immunization program performance. Community based household surveys are frequently used to assess coverage within a country. In household surveys to assess routine immunization coverage, a child's vaccination history is classified on the basis of observation of the immunization card, parental recall of receipt of vaccination, or both; each of these methods has been shown to commonly be inaccurate. The use of serologic data as a biomarker of vaccination history is a potential additional approach to improve accuracy in classifying vaccination history. However, potential challenges, including the accuracy of serologic methods in classifying vaccination history, varying vaccine types and dosing schedules, and logistical and financial implications must be considered. We provide historic and scientific context for the potential use of serologic data to assess vaccination history and discuss in detail key areas of importance for consideration in the context of using serologic data for classifying vaccination history in household surveys. Further studies are needed to directly evaluate the performance of serologic data compared with use of immunization cards or parental recall for classification of vaccination history in household surveys, as well assess the impact of age at the time of sample collection on serologic titers, the predictive value of serology to identify a fully vaccinated child for multi-dose vaccines, and the cost impact and logistical issues on outcomes associated with different types of biological samples for serologic testing.

Vaccine preventable diseases: time to re-examine global surveillance data?

While data driven estimates of the global burden of disease for some vaccine preventable diseases (VPDs) are limited, aggregate case numbers of VPDs are reported annually by country in the Joint Reporting Form (JRF). We examined pertussis surveillance data in the JRF, and vaccine coverage estimates, in comparison to measles, which is a priority disease for elimination and eradication efforts and is supported by the WHO Global Measles and Rubella Laboratory Network. In 2012, highest pertussis case numbers and incidence were reported from high income countries with high vaccine coverage, discordant with countries that had low vaccine coverage. Use of laboratory diagnostics for pertussis cases varied among countries. In contrast, highest reported numbers of measles cases and incidences tended to occur in low income countries. These observations imply poor quality global surveillance data for some VPDs, limiting capacity for monitoring global epidemiology or making vaccination policy decisions. Efforts are needed to improve the availability of quality surveillance data for all VPDs.

Critical issues in implementing a national integrated all-vaccine preventable disease surveillance system.

In 2007, the World Health Organization published the Global Framework for Immunization Monitoring and Surveillance (GFIMS) outlining measures to enhance national surveillance for vaccine preventable diseases (VPDs). The GFIMS emphasized that VPD surveillance should be integrated and placed in a 'unified framework' building upon the strengths of existing surveillance systems to prevent duplication of activities common to all surveillance systems and to minimize human resource and supply expenditures. Unfortunately, there was little experience in actually developing integrated VPD surveillance. We describe the process of developing operational guidance for ministries of health to implement such an integrated surveillance system for multiple VPDs.

Validity of vaccination cards and parental recall to estimate vaccination coverage: a systematic review of the literature.

Immunization programs frequently rely on household vaccination cards, parental recall, or both to calculate vaccination coverage. This information is used at both the global and national level for planning and allocating performance-based funds. However, the validity of household-derived coverage sources has not yet been widely assessed or discussed. To advance knowledge on the validity of different sources of immunization coverage, we undertook a global review of literature. We assessed concordance, sensitivity, specificity, positive and negative predictive value, and coverage percentage point difference when subtracting household vaccination source from a medical provider source. Median coverage difference per paper ranged from -61 to +1 percentage points between card versus provider sources and -58 to +45 percentage points between recall versus provider source. When card and recall sources were combined, median coverage difference ranged from -40 to +56 percentage points. Overall, concordance, sensitivity, specificity, positive and negative predictive value showed poor agreement, providing evidence that household vaccination information may not be reliable, and should be interpreted with care. While only 5 papers (11%) included in this review were from low-middle income countries, low-middle income countries often rely more heavily on household vaccination information for decision making. Recommended actions include strengthening quality of child-level data and increasing investments to improve vaccination card availability and card marking. There is also an urgent need for additional validation studies of vaccine coverage in low and middle income countries.