Immunization

  • Agarwal, S, Bhanot, A, Goindi, G. (2005). Understanding and Addressing Childhood Immunization Coverage in Urban Slums. Indian Pediatrics, 42(7), 653-63.
    • Urban poor, many residing in slums, comprise about a quarter of India’s urban population. Immunization coverage among urban poor children is a dismal 43%. This paper attempts to understand the current scenario and challenges in improving immunization coverage in urban slums in India.  It also discusses possible mechanisms for effectively reaching the often left-out urban poor. Coordinated activities by the multitude of providers, accurate information based outreach, effective monitoring and community enablement to demand quality services are critical for improving utilization of immunization services by a heterogeneous urban poor population.
  • Andrus JK, de Quadros CA, Solórzano CC, et al. (2011). Measles and rubella eradication in the Americas. Vaccine, 29(S4), D91-96.
    • The challenge for regions embarking on measles elimination will be to maintain high population immunity with excellent vaccination coverage and high-quality surveillance. Meeting this challenge will be especially critical for dealing with importations of measles virus that will occur as long as the virus is circulating anywhere in the world. Implementation of measles elimination strategies will uncover the hidden disease burden of rubella and congenital rubella syndrome. As was the experience in countries of Latin America and the Caribbean (LAC), integrating the elimination of measles with the elimination of rubella will greatly enhance the capacity of countries to sustain progress in the reduction of measles mortality. Countries of LAC prioritized the routine national immunization program over short-term successes. While doing so, they have also encountered new opportunities to expand the benefits of disease control and elimination activities to other aspects of public health, most importantly towards improving health care for women and newborns and reducing inequities in health in the region’s poorest communities. Implementation of similar strategies could lead to the global eradication of measles, rubella, and congenital rubella syndrome early this century, while strengthening routine immunization programs, and developing the capacity to introduce new and underutilized vaccines.
  • Assi TM, Brown ST, Kone S, et al. (2013). Removing the regional level from the Niger vaccine supply chain. Vaccine, 31(26), 2828-34.
    • These authors created a detailed simulation model of Niger’s vaccine supply chain and compared the current four-tier structure with a modified three-tier structure to investigate if removing a level could improve efficiency. They conclude that removing the regional level from Niger’s vaccine supply chain could substantially improve vaccine availability as long as certain adjustments to shipping policies and frequencies are implemented.  
  • Burton A, Monasch R, Lautenbach B, et al. (2009). WHO and UNICEF estimates of national infant immunization coverage: methods and processes. Bulletin of the World Health Organization, 87(7), 535-41.
    • WHO recommends that all children receive one dose of bacille Calmette-Guérin vaccine (BCG), three doses of diphtheria–tetanus–pertussis vaccine (DTP), three doses of either oral polio vaccine (OPV) or inactivated polio vaccine (IPV), three doses of hepatitis B vaccine, and one dose of a measles virus-containing vaccine (MVCV), either anti-measles alone or in combination with other antigens. This paper reports on review methodology to ascertain trends in infant immunization coverage.
  • Centers for Disease Control and Prevention (CDC). (2007). Elimination of measles–South Korea, 2001-2006. Morbidity and Mortality Weekly Report, 56(13), 304-07.
    • From 2000-01, South Korea experienced a measles epidemic that affected tens of thousands of children. In response, in 2001, South Korea announced a 5-year National Measles Elimination Plan. This report describes the activities and summarizes the results of that plan, which enabled South Korea to announce in late 2006 that interruption of indigenous measles transmission had been achieved, making South Korea the first country in the World Health Organization’s Western Pacific Region declare measles eliminated.
  • Dabbagh A, Patel MK, Dumolard L, et al. (2017). Progress Toward Regional Measles Elimination — Worldwide, 2000–2016. Morbidity and Mortality Weekly Report. 66(42), 1148.
    • This report updates a previous report (Patel et al., 2016) and describes progress toward global measles control milestones and regional measles elimination goals during 2000–2016. During this period, annual reported measles incidence decreased 87%, from 145 to 19 cases per million persons, and annual estimated measles deaths decreased 84%, from 550,100 to 89,780. Measles vaccination prevented an estimated 20.4 million deaths. However, the 2015 milestones have not yet been met and only one WHO region has been verified as having eliminated measles. Improved implementation of elimination strategies by countries and their partners is needed, with focus on increasing vaccination coverage through substantial and sustained additional investments in health systems, strengthening surveillance systems, using surveillance data to drive programmatic actions, securing political commitment, and raising the visibility of measles elimination goals.
  • Datta SS, O’Connor PM, Jankovic D, et al. (2018). Progress and challenges in measles and rubella elimination in the WHO European Region. Vaccine, 36(36), 5408-15.
    • Despite the availability of safe and cost-effective vaccines to prevent it, measles remains a significant cause of death among children under five years of age globally. The World Health Organization European Region has witnessed a drastic decline in measles and rubella cases in recent years. However, programmatic challenges exist in disease surveillance, vaccination service delivery and communication in endemic countries and should be addressed through periodic evaluation of the strategies by all stakeholders and exploring additional opportunities to accelerate the ongoing elimination activities. 
  • Duclos P, Okwo-Bele JM, Gacic-Dobo M, et al. (2009). Global immunization: status, progress, challenges and future. BMC International Health and Human Rights, 9(S1), 2-13.
    • Vaccines have made a major contribution to public health, including the eradication of one deadly disease, smallpox, and the near eradication of another, poliomyelitis. Through the introduction of new vaccines, such as those against rotavirus and pneumococcal diseases, and with further improvements in coverage, vaccination can significantly contribute to the achievement of the health-related United Nations Millennium Development Goals. The Global Immunization Vision and Strategy (GIVS) was developed by WHO and UNICEF as a framework for strengthening national immunization programmes and protect as many people as possible against more diseases by expanding the reach of immunization, including new vaccines, to every eligible person. This paper briefly reviews global progress and challenges with respect to public vaccination programmes.
  • Durrheim DN, Crowcroft NS, Strebel PM. (2014). Measles – The epidemiology of elimination. Vaccine, 32(51), 6880-83.
    • The Global Vaccine Action Plan has targeted measles elimination in at least five of the six World Health Organisation Regions by 2020. This is an ambitious goal, as measles control requires the highest immunization coverage of any vaccine-preventable disease. Importations can also result in local transmission and outbreaks in areas that have interrupted local endemic measles circulation. One of the lines of evidence that countries and Regions must address to confirm measles elimination is a detailed description of measles epidemiology over an extended period. This information is incredibly valuable as predictable epidemiological patterns emerge as measles elimination is approached and achieved. These patterns are discussed with illustrative examples from the Region of the Americas, which eliminated measles in 2002, and the Western Pacific Region, which has established a Regional Verification Commission to review progress towards elimination in all member countries.
  • Hinman AR, Hutchins SS, et al. (2004). Elimination of Measles and of Disparities in Measles Childhood Vaccine Coverage among Racial and Ethnic Minority Populations in the United States. Journal of Infectious Diseases,189(S1), 146-52.
    • The gap in measles vaccine coverage between white and nonwhite children was as large as 18% in 1970. During the measles epidemic of 1989–1991, attack rates among nonwhite children <5 years of age were 4–7 fold higher than rates among white children. Because of the epidemic and of the known disparity in vaccine coverage and risk of disease, a dual strategy to eliminate measles in the United States was implemented: universal interventions likely to reach the majority of children and targeted interventions more likely to reach nonwhite children. By 1992, the gap in coverage between white and nonwhite children was reduced to 6% and the risk of disease among nonwhite children was narrowed. During the 1990s, further implementation of the dual strategy resulted in narrowing the gap in vaccine coverage to 2% and elimination of endemic disease in all racial and ethnic populations. This dual strategy deserves close scrutiny by health professionals and policy makers in devising programs to meet future health objectives.
  • Hinman AR, Orenstein WA, Papania MJ. (2004). Evolution of Measles Elimination Strategies in the United States. Journal of Infectious Diseases, 189(S1), 17-22.
    • There have been 3 efforts to eliminate measles from the United States since the introduction of measles vaccine in 1963. This article discusses 10 major lessons to be learned from these elimination efforts. 
  • Haji A, Lowther S, Ngan’ga Z, et al. (2016). Reducing routine vaccination dropout rates: evaluating two interventions in three Kenyan districts, 2014. BMC Public Health, 16, 152.
    • Globally, vaccine-preventable diseases are responsible for nearly 20% of deaths annually among children younger than 5 years old. Worldwide, many children drop out from vaccination programs, are vaccinated late, or incompletely vaccinated. Here, Haji and colleagues evaluated the impact of text messaging and sticker reminders to reduce dropouts from the vaccination program. They found that text message reminders reduced vaccination dropout rates in Kenya and recommend the extended implementation of text message reminders in routine vaccination services.
  • Humpreys G. (2011). Vaccination: rattling the supply chain. Bulletin of the World Health Organization, 89(5), 324-25.
    • The introduction of new vaccines, combined with a push to expand immunization globally to reach every child, is straining vaccine supply chains to the limit. This article advocates for new thinking regarding the way vaccines are delivered.
  • Janusz CB, Castañeda-Orjuela C, Molina Aguilera IB, et al. (2015). Examining the cost of delivering routine immunization in Honduras. Vaccine, 33(S1), A53-59.
    • Many countries have introduced new vaccines and expanded their immunization programs to protect additional risk groups, thus raising the cost of routine immunization delivery. Honduras recently adopted two new vaccines, and the country continues to broaden the reach of its program to adolescents and adults. In this article, the authors estimate and examine the economic cost of the Honduran routine immunization program for the year 2011.
  • Kamadjeu R, Assegid K, Naouri B, et al. (2011). Measles Control and Elimination in Somalia: The Good, the Bad, and the Ugly. Journal of Infectious Diseases, 204(S1), 312-17.
    • Despite enormous challenges, Somalia has been successfully implementing accelerated measles control activities. Through innovative strategies and with the support of local and international partners, the country has shown potentials of implementing measles mortality reduction activities in complex emergencies. However, the near collapse of the health care system and the ongoing insecurity continue to hamper the implementation of recommended measles control and elimination strategies in some parts of the country, making these achievements fragile.
  • Kartoglu U, Milstien J. (2014). Tools and approaches to ensure quality of vaccines throughout the cold chain. Expert Review of Vaccines, 13(7), 843-54.
    • Cold chains have been developed for the transport and storage of heat liable vaccines and established in all countries, despite limited access to resources and electricity in the poorest areas. However, cold chain issues occur in all countries. Recent changes to vaccines and vaccine handling include the development and introduction of new vaccines with a wide range of characteristics, improvement of heat stability of several basic vaccines, observation of vaccine freezing as a real threat, development of regulatory pathways for both vaccine development and the supply chain, and emergence of new temperature monitoring devices that can pinpoint and avoid problems. With such tools, public health groups have now encouraged the development of vaccines labeled for use in flexible cold chains and these tools should be considered for future systems.
  • Kaufmann JR, Miller R, Cheyne J. (2011). Vaccine Supply Chains Need To Be Better Funded And Strengthened, Or Lives Will Be At Risk. Health Affairs, 30(6), 1113-21.
    • In the next decade, at least twelve additional vaccines that target such diseases as typhoid, malaria, and dengue will become available to lower- and middle-income countries. These vaccines must travel along what are called supply chains, which include all personnel, systems, equipment, and activities involved in ensuring that vaccines are effectively delivered from the point of production to the people who need them. But for various reasons, supply chains are already strained in many developing countries, and the potential inability to distribute new vaccines will place lives at risk. Among the many steps needed to strengthen the global vaccine supply chain, we suggest that the international community pursue improved coordination between organizations that donate and ship vaccines and the host-country officials who receive and distribute the vaccines, as well as better training for supply-chain managers.
  • Kieny MP, Costa A, Hombach J, et al. (2006). A global pandemic influenza vaccine action plan. Vaccine, 24(40-41), 6367-70.
    • In case of an influenza pandemic, the world will be in a situation where potential vaccine supply will fall short by several billion doses from global needs. In 2006, the World Health Organization convened a consultation of stakeholders in influenza vaccines and immunization to identify practical solutions to fill this gap. The consultation resulted in a global action plan outlining promising specific strategies to increase influenza vaccine production and surge-capacity before and during an influenza pandemic.
  • Kumru OS, Joshi SB, Smith DE, et al. (2014). Vaccine instability in the cold chain: Mechanisms, analysis and formulation strategies. Biologicals, 42(5), 237-59.
    • Instability of vaccines often emerges as a key challenge during clinical development (lab to clinic) as well as commercial distribution (factory to patient). To yield stable, efficacious vaccine dosage forms for human use, successful formulation strategies must address a combination of interrelated topics including stabilization of antigens, selection of appropriate adjuvants, and development of stability-indicating analytical methods. This review covers key concepts in understanding the causes and mechanisms of vaccine instability. Several illustrative case studies are described regarding mechanisms of vaccine instability along with formulation approaches for stabilization within the vaccine cold chain. 
  • Muscat M, Bang H, Wohlfahrt J, et al. (2009). Measles in Europe: an epidemiological assessment. Lancet, 373(9661), 383-89.
    • Measles persists in Europe despite the incorporation of the measles vaccine into routine childhood vaccination programmes more than 20 years ago. The aim of this study was to review the epidemiology of measles in relation to the goal of elimination of measles by 2010.
  • Orenstein WA. (2006). The Role of Measles Elimination in Development of a National Immunization Program. The Pediatric Infectious Disease Journal, 25(12), 1093-101.
    • 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. This article summarizes key lessons from these efforts.
  • Orenstein WA, Hinman AR. (1999). The immunization system in the United States — The role of school immunization laws. Vaccine. 17(S3), 19-24.
    • School immunization laws have had a remarkable impact on vaccine-preventable diseases in the United States, particularly in school-aged populations. Enforcement of laws through the exclusion of unvaccinated children from school is a critical factor in assuring success. All laws have exemptions for medical contraindications, 47 states have exemptions for persons with strong religious beliefs against vaccination and 15 states have exemptions for persons philosophically opposed to vaccination. Although school immunization laws establish a safety net to assure high levels of coverage, they cannot replace efforts to assure age-appropriate immunization in the first two years of life.
  • Orenstein WA, Cairns L, Hinman A, et al. (2018). Measles and Rubella Global Strategic Plan 2012–2020 midterm review report: Background and summary. Vaccine, 36(S1),  A35-42.
    • The eradication of both measles and rubella is considered to be feasible, beneficial, and more cost-effective than high-level control. The Measles and Rubella Initiative published a Global Measles and Rubella Strategic Plan, 2012–2020, which aimed to achieve measles and rubella elimination in at least five WHO regions by end-2020. This article presents results from document reviews and stakeholder interviews regarding progress toward this goal. The team concluded that, although significant progress in measles elimination had been made, progress had slowed. Detailed recommendations for strategies, governance, and resource mobilization are also outlined.
  • Orenstein WA, Papania MJ, Wharton ME. (2004). Measles Elimination in the United States. Journal of Infectious Diseases, 189(S1), 1-3.
    • In this article, Orenstein and colleagues cover in detail the history of measles elimination efforts in the United States starting in 1962 with the licensure of the first measles vaccines. They discuss lessons learned from major efforts and their implications for future efforts.
  • Patel MK. (2016). Progress Toward Regional Measles Elimination — Worldwide, 2000–2015. Morbidity and Mortality Weekly Report, 65(44), 1228-33.
    • This report describes progress toward global measles control milestones and regional measles elimination goals during 2000–2015. During this time, an estimated 20.3 million deaths were prevented by measles vaccination, and measles incidence decreased 75%, from 146 to 36 cases per 1 million population. The number of countries providing the second dose of measles-containing vaccine (MCV2) nationally through routine immunization services increased to 160 (82%) in 2015, and global MCV2 coverage was 61%. In 2015, a total of 184 million persons were vaccinated against measles during supplementary immunization activities. Although measles vaccination has saved millions of lives since 2000, data indicate that the progress toward elimination goals has slowed since 2010.
  • PATH, World Health Organization. (2011). An Assessment of Vaccine Supply Chain and Logistics Systems in Thailand. Seattle: PATH.
    • Improper storage and transportation can put vaccine products at risk of degradation. Therefore, an effective vaccine supply chain and logistics system is essential to ensure product quality. In 2009, the government of Thailand launched a pilot project to outsource vaccine supply management and distribution to the Government Pharmaceutical Organization (GPO), which in turn introduced and managed a vendor-managed inventory system (VMI) and subcontracted with a private logistics company to distribute vaccine products. The system gradually expanded nationwide by late 2010. Given the lack of empirical evidence to support the benefits of VMI or the benefits of outsourcing vaccine distribution to the GPO, this report sought to better understand the vaccine supply chain system in Thailand and the challenges of implementing the VMI system.
  • Peltola H, Heinonen OP, Valle M, et al. (1994). The Elimination of Indigenous Measles, Mumps, and Rubella from Finland by a 12-Year, Two-Dose Vaccination Program. New England Journal of Medicine, 331(21), 1397-402.
    • In the 1970s measles, mumps, and rubella were rampant in Finland, and rates of immunization were inadequate. In 1982 a comprehensive national vaccination program began in which two doses of a combined live-virus vaccine were used. This report details metrics of interest including rates of vaccination, adverse reactions, the incidence of disease, and other epidemiologic variables during the course of the program
  • Results for Development. (2017). Immunization Financing: A Resource Guide for Advocates, Policymakers, and Program Managers. Washington: Results for Development.
    • This resource guide collects 26 brief documents on topics related to the cost and financing of national immunization programs in low- and middle-income countries. Some of the briefs explore possible financing sources. Others examine the components and drivers of immunization costs, planning and decision-making processes related to immunization programs and budgets, and the relationship between immunization and broader health system financing. The guide concludes with a set of country case studies that illustrate particular approaches or important challenges.
  • Spika JS, Wassilak S, Pebody R, et al. (2003). Measles and Rubella in the World Health Organization European Region: Diversity Creates Challenges. Journal of Infectious Diseases 187(S1), 191-97.
    • Since 1984, the World Health Organization European Region has had targets for reducing the burden of a number of communicable diseases. The cultural and economic diversity of the region presents several challenges that must be overcome before regional targets are met. This piece discusses how diversity, including social factors, political will, economic costs, and communication can create benefits and risks associated with immunization. 
  • Thompson KM, Duintjer Tebbens RJ. (2016). Framework for Optimal Global Vaccine Stockpile Design for Vaccine-Preventable Diseases: Application to Measles and Cholera Vaccines as Contrasting Examples. Risk Analysis, 36(7), 1487-509.
    • Managing the dynamics of vaccine supply and demand represents a significant challenge with very high stakes. Insufficient vaccine supplies can necessitate rationing, lead to preventable adverse health outcomes, delay the achievements of elimination or eradication goals, and/or pose reputation risks for public health authorities and/or manufacturers. This article explores the dynamics of global vaccine supply and demand to consider the opportunities to develop and maintain optimal global vaccine stockpiles for universal vaccines, characterized by large global demand, and nonuniversal vaccines. 
  • UNICEF. (2016). Immunization Supply Chain Management. New York: UNICEF
    • Developed jointly by UNICEF and WHO, this resource is an advanced e-course that provides training in areas deemed vital to the advancement of the Global Vaccine Action Plan and its vision that everyone lives a life free from vaccine-preventable disease.
  • Wallace AS, Bohara R, Stewart S, et al. (2017). Impact of an Intervention to Use a Measles, Rubella, and Polio Mass Vaccination Campaign to Strengthen Routine Immunization Services in Nepal. Journal of Infectious Diseases. 216(S1), 280-86.
    • The potential to strengthen routine immunization services through supplementary immunization activities is an important benefit of global measles and rubella elimination and polio eradication strategies. However, little evidence exists on how best to use supplementary immunization activities to strengthen routine immunization. As part the 2012 Nepal measles-rubella and polio supplementary immunization activities, these authors developed an intervention package designed to improve routine immunization processes and evaluated its effect on specific routine immunization process measures.
  • Weldegebriel GG, Gasasira A, Harvey P, et al. (2011). Measles Resurgence Following a Nationwide Measles Vaccination Campaign in Nigeria, 2005–2008. Journal of Infectious Diseases, 204(S1), 226-31.
    • From 1990 through 2008, routine immunization coverage of measles vaccine in Nigeria ranged from 35% to 70%. Nigeria conducted a nationwide measles vaccination campaign in 2 phases during 2005–2006 that targeted children aged 9 months to 14 years; in 2008, a nationwide follow-up campaign that targeted children aged 9 months to 4 years was conducted in 2 phases. Despite these efforts, measles cases continued to occur. This descriptive study reviewed the measles immunization coverage data from administrative, World Health Organization, United Nations Children’s Fund, survey, and supplemental immunization activities data. 
  • Woodle D. (2000). Vaccine procurement and self-sufficiency in developing countries. Health Policy and Planning, 15(2), 121-29.
    • This paper discusses the movement toward self-sufficiency in vaccine supply in developing countries and explains special supply concerns about vaccines as a product class. It also provides information about a vaccine procurement manual being developed by the United States Agency for International Development (USAID) and the World Health Organization (WHO) for use in this environment. Two brief case studies are included to illustrate the spectrum of existing capabilities and different approaches to technical assistance aimed at developing or improving vaccine procurement capability. In conclusion, the paper discusses the special nature of vaccine and issues surrounding potential integration and decentralization of vaccine supply systems as part of health sector reform.
  • World Health Organization. (2014). Immunization Supply Chain and Logistics: A neglected but essential system for national immunization programmes. Geneva: WHO.
    • Immunization Supply Chain and Logistics (ISCL) systems have supported the achievement of acceptable vaccination coverage, using coping mechanisms to overcome enduring challenges in vaccine storage, distribution and management. However, the growth in complexity of immunization programs has resulted in opportunities for improvement. This report outlines recommendations for national-level programs and for the global community of partners to improve the performance of ISCL systems. 
  • World Health Organization. (2012). Global Measles and Rubella: Strategic Plan (2012-2020). Geneva: WHO
    • This strategic plan explains how countries, working together with the MR Initiative and its partners, will achieve a world without measles, rubella and congenital rubella syndrome (CRS). The Plan builds on the experience and successes of a decade of accelerated measles control efforts that resulted in a large reduction in measles deaths globally between 2000 and 2010. It integrates the newest 2011 World Health Organization (WHO) policy on rubella vaccination which recommends combining measles and rubella control strategies and planning efforts, given the shared surveillance and widespread use of combined measles-rubella vaccine formulations. The Plan presents clear strategies that country immunization managers, working with domestic and international partners, can use as a blueprint to achieve the 2015 and 2020 measles and rubella control and elimination goals.
  • World Health Organization. (2011). Global Immunization Vision and Strategy. Geneva: WHO.
    • In response to challenges in global immunization, WHO and UNICEF developed the Global Immunization Vision and Strategy (GIVS). Launched in 2006, GIVS is a ten-year Framework aimed at controlling morbidity and mortality from vaccine-preventable diseases and helping countries to immunize more people, from infants to seniors, with a greater range of vaccines. GIVS provides over two dozen strategies from which countries can choose for implementation according to their specific needs.
  • World Health Organization. (2011). Global Vaccine Action Plan. Geneva: WHO.

    • The Global Vaccine Action Plan (GVAP) – endorsed at the 2012 World Health Assembly – is a framework to prevent millions of deaths by 2020 through more equitable access to existing vaccines for people in all communities.

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  • World Health Organization. (2003). WHO-recommended standards for surveillance of selected vaccine-preventable diseases. Geneva: WHO.
    • The purpose of this document is to provide WHO recommendations on surveillance standards for selected vaccine-preventable diseases. The recommendations should be carefully adapted to meet national needs in accordance with each country’s disease control priorities, objectives, and strategies.
  • Zaffran M, Vandelaer J, Kristensen D, et al. (2013). The imperative for stronger vaccine supply and logistics systems. Vaccine, 31(S2), B73-80.
    • With the introduction of new vaccines, developing countries are facing serious challenges in their vaccine supply and logistics systems. Storage capacity bottlenecks occur at national, regional, and district levels and system inefficiencies threaten vaccine access, availability, and quality. As countries adopt newer and more expensive vaccines and attempt to reach people at different ages and in new settings, their logistics systems must be strengthened and optimized.
  • Zell ER, Ezzati-Rice TM, Battaglia, MP, et al. (2000). National Immunization Survey: the methodology of a vaccination surveillance system. Public Health Reports, 115(1), 65-77.
    • The National Immunization Survey (NIS) was designed to measure vaccination coverage estimates for the US, the 50 states, and selected urban areas for children ages 19-35 months. The NIS includes a random-digit-dialed telephone survey and a provider record check study. Data are weighted to account for the sample design and to reduce nonresponse and non-coverage biases in order to improve vaccination coverage estimates. Adjustments are made for biases resulting from nonresponse and non-telephone households, and estimation procedures are used to reduce measurement bias. The NIS coverage estimates represent all US children, not just children living in households with telephones. NIS estimates are highly comparable to vaccination estimates derived from the National Health Interview Survey. The NIS allows comparisons between states and urban areas over time and is used to evaluate current and new vaccination strategies.