June 24, 2015
In a previous web article we explored how improvements in immunization rates over the past three decades have plateaued, leaving substantial gaps in coverage.
Four diseases—diphtheria, measles, pertussis (whooping cough), and tetanus—were responsible for an estimated 218,400 deaths worldwide in 2013, yet just two combination vaccines, DTP and MCV, can protect children from these diseases.
Global coverage for both vaccinations has hovered around 84 percent for the past five years. And national rates tell only part of the story. In 2013, more than 70 percent of countries failed to achieve 80 percent DTP3 coverage in every district or equivalent administrative unit.
The Global Vaccine Action Plan (GVAP), developed by key stakeholders including UNICEF and the World Health Organization (WHO), sets out two key measures of success for immunization by 2020:
Goals in the United States are similar to the GVAP goals. The U.S. Healthy People 2020 plan sets a target of 90 percent coverage among children ages 19 to 35 months for four doses of DTP and at least one dose of MCV.1
Gaps and disparities in immunization coverage remain for many reasons, ranging from cost to parents’ confidence in the vaccines. Challenges persist on both the supply and the demand side. A comprehensive strategy should address both.
On the vaccine supply side, inaccurate forecasting and management of vaccine stocks can mean that an adequate supply of vaccines may not always be available.
Effective delivery of vaccines remains a problem in many parts of the world, particularly in remote, impoverished, or strife-torn areas that are difficult to reach due to geography, weak or nonexistent health systems, or other structural barriers (nomadic populations, language, or literacy gaps). Global immunization efforts were able to completely eradicate smallpox, and it was hoped that polio would be the next vaccine-preventable disease to be wiped out. Unfortunately barriers to vaccination coverage have prevented polio eradication.
Most vaccines require a “cold chain,” a process which ensures they are kept within an optimal temperature range (approximately 2 C to 8 C) from the time they are produced to when they are used. When exposed to temperatures outside this range, vaccines can lose their potency or even become ineffective. In many places, particularly in hot climates with distant, hard to reach areas, this “cold chain” is inadequate for effective transport, storage, and handling of all needed vaccines.
In addition, despite discounted prices, the cost of vaccines can still pose a barrier to coverage. Given resource constraints and competing priorities, needed vaccines still remain out of reach for many low income countries.
Immunization policies linked to school enrollment can also affect vaccination coverage. For example in the United States, all states have immunization requirements for public school enrollment, though they allow religious exemptions and medical exemptions due to illness or allergy.2 Several states also make allowances beyond these two exemptions. These broad vaccination exemption policies make it easier for parents to skip some or all vaccinations for their children, even without a documented medical or religious reason. Parental misunderstanding of vaccine safety and efficacy, mistrust of the government, and lack of awareness of the risks posed by infectious diseases are common reasons for seeking exemptions.3
Parental knowledge and concerns about the safety and effectiveness of vaccinations are also not uncommon outside the United States. Recent studies in Nigeria and Pakistan, where a large majority of unvaccinated children live, found that low education levels, lack of knowledge, and negative attitudes toward immunization among parents pose important barriers.4
Beyond vaccination-specific knowledge or beliefs, one study in Pakistan revealed that vaccination rates were lower among children whose mothers did not use health services such as antenatal care or delivery.5 Perhaps because they had limited interaction with the health system, mothers did not receive messages about immunization, or a general lack of trust in the health system may have prevented them from using services in the first place.
GVAP lays out a roadmap for achieving immunization goals. The plan follows six guiding principles: country ownership, shared responsibility and partnership, equity, integration, sustainability, and innovation.
On the supply side, GVAP recommends that countries prioritize immunization by setting ambitious targets and ensuring that the appropriate infrastructure and human resources are in place for implementation and monitoring.
In addition, it will be crucial to maintain adequate funding and to ensure that high-quality vaccines remain affordable over the long term. Moreover, strong immunization programs should be integrated within a broader well-functioning health system. This effort will require health systems strengthening, building the capacity of frontline health care workers, improving monitoring and surveillance, and coordinating the delivery of services.
Many other infectious diseases threaten public health. Illnesses such as malaria and HIV have serious health consequences, yet no vaccine exists today to protect against those diseases. To address this gap, targeted and innovative research is needed to develop effective new vaccines and to accelerate their licensing, delivery, and use.
In the United States, school-enrollment immunization laws have been successful in increasing immunization coverage rates, although exemption policies weaken the effect. Because exemption policies increase the risk that infectious diseases will spread, the American Medical Association announced recently they “will seek more stringent state immunization requirements to allow exemptions only for medical reasons.”6
Moving forward, it will be important to increase confidence in and demand for immunization. Broad-based communication and advocacy efforts can achieve this aim by ensuring that individuals and communities understand the benefits and risks of immunization and view it as both their right and responsibility.
Demand-side programs can be quite effective. One study in Pakistan found that a simple community-based health education program for a low-literate population improved DTP3/Hepatitis B vaccine completion rates by 39 percent.7 Another study in the same country, found a two to threefold increase in the likelihood of DTP and measles vaccination use in communities that received an intervention involving a fact-based discussion of vaccination costs and benefits.8 In addition, simple interventions like reminder systems can have a strong positive effect on demand for vaccinations and thus, improvements in vaccination coverage.9