Global Immunization: Controlling the Spread of Disease
Because no country in the world exists in complete isolation, control of diseases must be collaborative. While communication between countries and regions must be open and disease tracking coordinated, public health approaches and vaccine schedules may vary depending upon disease rates, population susceptibility and public health resources.
Tracking disease and measuring vaccine success
Types of vaccination programs
Goals for vaccination programs
Variation among vaccine schedules
Tracking disease and measuring vaccine success
The World Health Organization (WHO) leads and coordinates issues pertaining to international health. WHO consists of 193 member countries and is organized into six regions:
- African Region
- Region of the Americas
- Eastern Mediterranean Region
- European Region
- South-East Asia Region
- Western Pacific Region
The work of the WHO is carried out by experts working with health officials in regional and local offices of countries in which they are employed, and by an extensive network of laboratories around the globe. These offices and labs confirm cases of disease, track changes to viruses and bacteria, track movement of diseases throughout the world, coordinate disease control efforts and monitor the success of interventions, such as vaccine programs.
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Types of vaccine programs
There are different types of vaccine programs. The best method varies depending on geography, disease prevalence, and culture. Vaccine coverage for a population can be accomplished by:
- Public sector immunization programs – Vaccines are provided by the government for the entire population. The U.K. has this type of program.
- Public and private sector immunization programs – Vaccines are distributed by both private healthcare providers and government programs. The U.S. has this type of program.
- Mass campaign – A limited time effort (e.g., one day) in which an entire portion of the population (e.g., all children less than 5 years old) is immunized regardless of previous immunization status. These types of campaigns may take place in a certain region or throughout an entire country. Polio eradication efforts have employed mass campaigns in many developing countries.
- Health centers or health posts – Established health centers in a country may provide immunizations on an ongoing basis or specially scheduled days. The Ministry of Health, a non-governmental organization, or a private provider may operate these centers.
- Mobile teams – Immunizations are distributed by teams that travel to villages or remote areas that may not have regular access to healthcare. Nepal and India are places in which these types of efforts have been employed.
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Goals for vaccine programs
The measure of success for different vaccine programs may vary, depending on the disease, geographic location and maturity of the vaccine program:
- Disease control is meant to decrease the occurrence of disease in a specific geographic area to an acceptable level.
- Elimination is meant to stop transmission of disease in a given geographic region. Polio has been eliminated from most, but not all areas of the world.
- Eradication is meant to reduce disease to zero worldwide. Smallpox is the only disease that has ever been successfully eradicated. A disease can be eradicated only if it has certain characteristics:
- Only be found in humans (not animals)
- Has an easily recognizable illness
- Not lead to long-term or chronic infection
- Has an effective intervention, such as a vaccine that provides long-lasting immunity
Successful meningitis vaccine program in Africa
There is significant excitement and hope surrounding a new vaccine that prevents a common type of meningitis in Africa. Meningitis A epidemics occur every 7-14 years in a region of sub-Saharan Africa known as the “meningitis belt.” During these epidemics, thousands die within a day or two of becoming ill. Of those who survive, about 15 of every 100 are left with permanent disabilities, including brain damage, hearing loss, or learning disabilities.
In 2001, the World Health Organization (WHO) and PATH, an international nonprofit dedicated to breaking the cycle of poor health, formed a partnership known as the Meningitis Vaccine Project. With support from the Bill and Melinda Gates Foundation, the partnership worked with African governments and various partners to develop a vaccine that would be effective and affordable in this region of the world.
After clinical trials showed the vaccine to be safe and effective, the vaccine known as MenAfriVac™ was made available. During December 2010, the country of Burkina Faso conducted a large-scale immunization program. Vaccine was made available for everyone in the country younger than 30 years old. The president attended kick-off celebrations, and families stood in lines to have their children immunized against the dreaded disease. Public health officials immunized about 11 million people in less than two weeks. Early disease surveillance results have excited public health officials. With the 100 millionth person vaccinated with MenAfriVac™ during the week of December 3, 2012, the Meningitis Vaccine Program is on track to accomplish its goal of immunizing 300 million people with the vaccine by 2015.
Learn more and watch videos about the project by visiting the Meningitis Vaccine Project website.
Update on polio eradication efforts
Administration of the polio vaccine has led to a tremendous decrease in the number of cases that occur throughout the world each year. During 2011, slightly more than 700 cases of polio occurred throughout the world, which was less than half the total number of cases that occurred the previous year.
There are three countries where polio transmission has never been successfully stopped. These include the African nation of Nigeria and the Asian countries of Afghanistan and Pakistan. In January 2012, India celebrated the first year in history in which no child was paralyzed by polio. Only one case was reported in that country over the one-year period.
While polio eradication efforts continue, there are different reasons for these strongholds of disease.
Nigeria - efforts in this region have suffered from vaccine safety concerns and political instability and corruption. A few years ago some people in the region refused vaccine out of unfounded concerns of contamination. Recent efforts have been hampered by a lack of government infrastructure and support as well as corruption. In 2008, Nigerian cases accounted for almost half of the worldwide total.
Afghanistan and Pakistan - the conflicts in this region have made optimal vaccine coverage difficult to achieve. In regions of both countries vaccine operations are not allowed. Similarly, even in regions where vaccine program agreements have been forged, there has been violence. In 2012, nine humanitarians working for a polio vaccination campaign in Pakistan were killed. In addition to compromising vaccine coverage, these unstable conditions have led to difficulties in monitoring disease spread.
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Variation among vaccine schedules
Vaccine schedules vary from country to country and sometimes even within countries. These differences can include which vaccines are recommended, who should get them, when they are given, and how many doses are needed. There are several reasons for this variation:
Why are different vaccines recommended?
- Economics – Because some countries cannot afford to give all vaccines to their at-risk populations, they must choose which diseases are most important to prevent through immunizations.
- Rates of disease – Because a disease may be an imminent threat in one place, but a minor threat elsewhere, different vaccines may be used routinely in different places. For example, because Japanese encephalitis virus (JEV) is not common in the U.S., it is not a routinely recommended vaccine. However, travelers who may be at risk of infection with JEV while traveling may be recommended to get the vaccine.
Why are different people recommended to get vaccines?
- Risks of disease - Some people are at a higher risk of developing a disease than others, so they are recommended to get particular vaccines. Increased risks may result from where they live, medical conditions that they have, their age or race, or their social habits. Globally, immunization programs are typically aimed at infants and young children, who usually are at greatest risk of complication or death if infected.
- Risk of adverse events - Some people should not get specific vaccines because they are at an increased risk of having an adverse reaction. These risks may include medical conditions or allergies.
Why are vaccines given at different ages?
- Age of exposure – Social circumstances, such as crowding and nutrition, as well as the amount of disease circulating in a community determine when a child is most likely to be exposed to a potentially deadly infectious disease. As a result, advisory bodies must study these data to determine when it is best to give a particular vaccine in their country or area.
- Risk of complications or lack of immune response – Advisory bodies must also consider whether there is a potential risk of experiencing adverse events from or non-response to the vaccine due to age. This is balanced against the potential for exposure to determine the best time to give a vaccine.
- Feasibility – New vaccines may be given at a time when other vaccines are already recommended to reduce the number of visits needed and to streamline the administrative system. A vaccine that is going to be given with other vaccines must be tested with those vaccines to be sure there is no cross-reactivity or loss of effectiveness among them; these studies are called concomitant use studies.
Why are there differences in the number of doses given?
- Disease presence in the community – When a vaccine is first offered, there is typically a large quantity of the virus or bacteria causing disease in the community. As people are exposed to these circulating agents, their protection against the disease is naturally boosted; it is like getting another dose of the vaccine, except you don't know that it has happened.
Once the vaccine has been used for several years, there is likely to be less disease and, therefore, less chance for people to come into contact with it. In some cases, this leads to the need for another dose of the vaccine, so that a person can stay protected.
- Vaccine differences – Vaccines are not the same worldwide. A vaccine against one disease may be made by several different companies and, therefore, be different products, consisting of different types, parts or forms of the same bacteria or virus or having different stabilizing or immune-enhancing agents.
- Supply and demand – When a vaccine is first given in a country, some governments require that a certain percentage of the population get the first dose of the vaccine before any additional doses can be given to individuals. This tends to happen in places where there are limited resources.
The World Health Organization recommends the following vaccines for all infants and young children: pneumococcal, rotavirus, rubella, tuberculosis, polio, diphtheria, tetanus, pertussis, hepatitis B and measles. Yellow Fever and Haemophilus influenzae type b vaccines are recommended for some populations.
The WHO offers a useful tool for vaccine schedules around the world. You can view information based upon country or region, vaccine (referred to as "antigen") or both.
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Updated: January 2013