Beyond vertical and horizontal programs: a diagonal approach to building national immunization programs through measles elimination

KEYWORDS:

• measles
• diagonal programming
• surveillance
• immunization infrastructure
• health systems strengthening

Plans for reducing and eventually eradicating measles globally include achieving and maintaining high vaccination coverage with two doses of measles containing vaccines (via routine and mass vaccination), monitoring disease, responding to outbreaks, building good communications, and implementing research and development to improve overall programs (e.g. health systems strengthening) [1]. Global progress on measles vaccination has saved millions of lives – an estimated 17.1 million between 2000 and 2014 – and has the potential to save many more, especially if countries begin using measles elimination to build up their overall national immunization programs [2].

Going beyond vertical and horizontal – diagonal programs

Horizontal programs are those in which health services are integrated (e.g. where all immunizations and other health interventions are available and implemented as appropriate) and are the typical approach in most resource-rich areas. However, in developing countries, disease control and prevention programs are often implemented vertically via disease-specific interventions implemented on a massive scale, usually with restricted funding (government and/or private) and varying degrees of country ownership. For example, the polio eradication program has relied heavily on mass campaigns to deliver oral polio vaccines (OPV) alone or with a limited number of additional services, such as insecticide-treated bed nets to prevent malaria, and vitamin A supplements. These campaigns are needed where routine immunization systems miss children, leading to failure to achieve the coverage levels required to interrupt polio transmission. Vertical programs are increasingly scrutinized because they miss opportunities to deliver other health-care services in favor of a narrow focus on achieving one goal, and staff and other resources may be diverted from the horizontal program to the vertical program, potentially decreasing the delivery of overall health-care services. Many fledgling programs in resource-poor settings lack the infrastructure to deliver comprehensive health care and rely on vertical programs. Some countries have attempted to use the resources provided for a vertical program to enhance their platforms for delivering comprehensive preventive and therapeutic care. The term ‘diagonal approach’ has been used to describe this approach by Sepulveda, Frenk, and others [3–6]. In Mexico, multiple ‘vertical’ interventions were integrated into the health system over a period of 25 years (1980–2005) and had a clear impact on reducing mortality in children [3,4]. Examples of leveraging the platform provided by vertical programs to deliver other services include targeting HIV control programs in sub-Saharan Africa to integrate breast and cervical cancer prevention services and building up a comprehensive HIV treatment program in Haiti, resulting in a revitalized health-care structure in 2003 [5–8].

Measles elimination as a case study for a diagonal approach

Political systems tend to respond better to real problems than theoretical ones. For instance, low vaccination coverage may lead to outbreaks of disease. But prior to the outbreak, high levels of susceptibility is a theoretical problem – not a real problem like increased morbidity and mortality – just the potential for an outbreak that would result in high numbers of cases of disease, disability, and death. Low vaccination and theoretical outbreaks can seem to laypersons or policy makers like meaningless numbers, since they are often confronted by ongoing real problems of poor health and other crises. Many politicians may be confronted by multiple persons advocating that their ‘disease’ or problem is the ‘big one’. On the other hand, illness and death from vaccine-preventable diseases especially during outbreaks are real problems that present narratives that, once measured and their stories told, can be used to compel government and public health entities to respond either by creating vertical programs or by using political momentum to build an overall system to address multiple programs.

Measles has two key qualities that uniquely render it a useful overall program indicator: contagiousness and presentation. The higher the R₀ of an infectious disease (a measure of contagiousness), the higher the immunity level in the population needed to prevent an outbreak. R₀ is the basic reproductive number, i.e. expected number of secondary cases produced by a single (typical) infection in a fully susceptible population. Thus, when evaluating immunization programs, the first disease likely to occur, when immunization coverage is less than optimal, is a disease with a high R₀, showing where in your system you have programmatic gaps. Measles has a very high R₀ of 12–18, meaning on average of 92–94% of the population must be immune to prevent spread of the disease [9]. Moreover, virtually every case of measles is clinically apparent with rash and fever with a limited differential diagnosis facilitating identification and obtaining specimens for laboratory confirmation. Further, measles is a cyclical disease. After an outbreak, susceptibility is reduced and remaining levels of disease are low, setting a new ‘social norm’ for acceptable levels of disease. However, in the absence of a good routine immunization program, susceptibles begin accumulating. After a period of years, there are enough susceptibles to fuel a large outbreak. Even if that outbreak is smaller than the previous one, it exceeds the social norm and hence the outbreak is considered unacceptable and can trigger interventions. These characteristics make measles control/elimination programs an ideal foundation on which to start building and unifying overall immunization programs with delivery of other health services.

For example, in the United States, measles elimination goals played a key role in the development of the National Immunization Program [10,11]. First licensed in the United States in 1963, measles vaccines were first provided through a new Federal Immunization Program in 1965, called the 317 program, the first new vaccine introduced since the program began. A goal was announced in 1966 to eliminate measles from the United States. Marked progress was made with a reduction in the annual incidence of measles from over 500,000 reported cases to approximately 22,000 cases in 1968. Instead of maintaining the effort, Federal funds were diverted to another new vaccine, introduced in 1969, rubella. Within 5 years, enough susceptibles to measles had accumulated to fuel the next outbreak and in 1971, a resurgence occurred. Some Federal funding was restored but was reduced after the peak of that outbreak and subsequent reduction in disease incidence. This set up the conditions that led to yet another resurgence in 1977. This time older school-aged children were the focus of transmission which triggered the enactment and enforcement of school immunization mandates, which not only included measles but other vaccines as well demonstrating how measles drove improved coverage for all vaccines. But the problem with measles was not over. Another resurgence in 1989–1991, primarily affected young, unvaccinated preschool children. During that resurgence, there were over 55,000 cases reported, more than 11,000 hospitalizations, and 123 deaths. This measles outbreak provided the political support for a presidential initiative on immunization focusing on improving the delivery infrastructure for all routine immunizations. Major legislation was enacted to finance immunizations for poor children, empowering the National Immunization Technical Advisory Group in the United States (Advisory Committee on Immunization Practices) to see its recommendations automatically financed. A vital strategy of the elimination program was targeting the detection of cases (vs. relying on vaccine coverage), which helped build a surveillance program allowing us to determine which cases were due to vaccine failure versus failure to vaccinate. Cases with vaccine failure led to recommendations for a two-dose schedule. Cases who should have been vaccinated but were not led to improvements in vaccine delivery. Focusing on surveillance as the primary outcome measure was a driving force. Surveillance delivered data that highlighted weaknesses in the immunization system and stories showing the consequences – actual measles outbreaks, captivating the attention of policy makers. The momentum we gained working to eliminate measles allowed us to develop several elements of what we now know makes a strong immunization program.

Similarly in China, efforts in the early 2000s to accelerate measles elimination and strengthen routine immunization in one province (Guizhou Province) provided a model for achieving these goals nationally [12]. The strategies outlined were strengthening routine vaccination, enforcement of school requirements, supplementary immunization activities, and strengthening measles surveillance. Case-based surveillance helped identify pockets of underimmunized children, helping the program target resources to prevent further spread. These approaches helped the government focus on emphasizing financing and accountability and facilitated the development of an internet-based registry system to improve accuracy of immunization records and further identify poor-performance areas all of which are applicable both to broader geographical areas as well as other disease control programs.

Approved by the World Health Assembly in 2012 to achieve the Decade of Vaccines vision by delivering universal access to immunization, the Global Vaccine Action Plan (GVAP) identified gaps and unmet needs in global immunization. The GVAP explicitly called for programs that are focused on one disease (like measles or polio) to build routine immunization strengthening into their plans and integrate into national programs rather than continue to operate independently [13,14]. The GVAP proposes that strengthening routine immunizations systems will improve global vaccination coverage. We support and champion these efforts and conversely, we propose that improving efforts to eliminate measles, if used appropriately, can provide immunization program managers a base for advocating for improvements in their overall national disease prevention and control programs.

Declaration of interests

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.