This section discusses several vaccines in depth and examines the impact of their development and advancement among populations.
Polio Vaccine
Polio vaccine being administered in Pakistan. Photo from: http://www.theguardian.com/global-development/2013/apr/02/pakistan-militants-polio-north-waziristan
Polio: A viral disease that affects the nerves. In severe cases, paralysis (full or partial) is well know symptom. Polio is transmitted by person-to-person contact or contact with infected mucus or fecal matter.
There are two vaccines for preventing poliomyelitis, both of which are highly effective: the injected polio vaccine (IPV), an inactivated vaccine, and the oral polio vaccine (OPV), a weakened live vaccine. OPV is cheaper and simpler to administer than IPV, confers lifelong immunity, and is the most used vaccine in developing countries. A very rare side effect of OPV is Vaccine Derive Paralytic Polio (VDPP), which occurs in approximately one out of 2.4 million vaccine doses distributed.
After just one dose, 50% of recipients will develop immunity to the 3 serotypes of poliovirus contained in trivalent OPV, and 95% of recipients become immune after 2 doses. IPV provides immunity in 90% of the recipients after 2 doses and 99% after 3 doses (CDC, The Pink Book, 2007). In 2005, the global coverage of infants with three doses of either type of polio vaccine was 78% (WHO, 2007). In 2008, the WHO and UNICEF estimated an 83% global coverage of polio immunization in infants (WHO 2008).
Polio has never been fully eradicated in Nigeria, Pakistan, Afghanistan, or India. Over the past few years, Polio has resurged in parts of Africa and the Middle East. By the spring of 2009, strains of the disease were appearing in Angola, Uganda, Chad, Niger, Sudan, and the Democratic Republic of Congo. Religious opposition to the vaccine is rumored to be among one of the reasons the disease has made a return (New York Times, April 20, 2009). Rumors of a sterilization plot by the West led to the resistance of immunizations by many Muslims from northern Nigeria and northern India. This dangerous myth caused a reversal in the progress made by more than 20 years of eradication efforts in these areas.
Wild Poliovirus (WPV) cases
Total cases | Year-to-date 2014 | Year-to-date 2013 | Total in 2013 |
Globally | 178 | 264 | 416 |
- in endemic countries | 159 | 79 | 160 |
- in non-endemic countries | 19 | 185 | 256 |
To see more about where polio cases are appearing currently, go to:
http://www.polioeradication.org/Dataandmonitoring/Poliothisweek.aspx
Tetanus Vaccine
Tetanus Vaccine being administered in Ghana. Photo from: http://ghanahealthnest.com/2012/09/05/what-is-tetanus-faqs/
Tetanus: The main symptom associated with this disease are spasms. The spasms can be mild or strong enough to tear muscles and fracture bones. Without treatment, one out of four infected people die. The death rate for newborns with untreated tetanus is even higher. With proper treatment, less than 10% of infected patients die ((Ncbi.nlm.nih.gov, 2011).
Tetanus has a very high fatality rate amoung neonates (Reingold, 2001). In 1989, the World Health Assembly declared that it was committed to the global elimination of neonatal tetanus by the year 1995, as worldwide eradication would lead to an estimated 10-25% reduction in infant mortality from all causes. The tetanus toxoid vaccine, routinely adminsitered with Diptheria and Polio (DPT/DPT3), provides protective immunity in the majority of those immunized after the second dose while the third dose induces immunity in almost 100% of those immunized. So far, the disease has been eliminated in over 100 developing countries. The vaccine is safe, provides almost 100% immunity for a 10-year period, and is relatively cheap - costing about US$1.20 to protect both mother and child against tetanus.
The tetanus vaccine is the only immunization routinely recommended by WHO for pregnant women in developing countries. In 1994, 48% of pregnant women had received at least two doses of the tetanus vaccine, but the disease still claims the lives of 200,000 neonates and infants a year in developing countries (WHO Vaccines history, 2005). Today, a two-dose coverage in pregnant women is still relatively low at 57% (WHO, 2007). As of December 2007, there are 47 countries have yet to eliminate maternal and neonatal tetanus (MNT).
Measles Vaccine
Measles: The infection is spread by contact with droplets from the nose, mouth, or throat of an infected person. Sneezing and coughing can put contaminated droplets into the air (Ncbi.nlm.nih.gov,2011b).
According to the WHO, the widespread global use of measles vaccines has resulted in annual reported cases falling from almost 4.5 million in 1982 to approximately 0.5 million in 1998. In 2000, Southern Africa joined the region of the Americas "as the second group of contiguous countries covering a large geographic area to be free from measles deaths” (Grabowsky et al, 2002, 716). Southern Africa implemented an immunization strategy initiated by the Pan American Health Organization (PAHO) that included vaccination through routine services and periodical mass campaigns, surveillance, and improved management of measles cases (Grabowsky et al, 2002).
However, measles continues to be a significant cause of morbidity and mortality worldwide, especially in developing countries, accounting for 26 million Disability Adjusted Life Years (DALYs). These deaths occurred mostly in countries with vaccine coverage of less than 50%. In some cases, measles epidemics have begun to reemerge due to waning vaccine coverage, which is currently at 83% of children receiving the first dose before their first birthday (WHO, 2007). As a next step for measles elimination, public health experts stress the need for routine administration of a single-dose measles vaccine to children as soon as possible after turning one, and the implementation of a two-dose schedule (Suzuki et al, 2002). If public health experts are successful, 95% of children vaccinated at the age of 1 and 98% of children vaccinated at 15 months of age will develop measles antibodies (CDC, The Pink Book, 2007).
In 2009, a dry powder inhalable version of the measles vaccine was developed. This live-attenuated and inhalable vaccine, for which human clinical trials started to develop in India in 2010, would be more practical to distribute in developing countries where needles, clean water, and refrigeration - all are required to properly store and administer the conventional measles vaccine - can be scarce. In tests done in rhesus macaques, the inhalable vaccine was found to be just as effective as the traditional vaccine (ABC News, August 2009).
Hepatitis B Vaccine
Hepatitis B: Is spread through having contact with the blood, semen, vaginal fluids, and other body fluids of an infected individual. Infants can contract it during child birth. Most of the damage from the hepatitis B virus occurs because of the way the body responds to the infection. When the body's immune system detects the infection, it sends out special cells to fight it off. However, these disease-fighting cells can lead to liver inflammation (Ncbi.nlm.nih.gov, 2011a).
About one-third of the world's population is believed to have been infected with Hepatitis B at some time during their life, though 90% of healthy adults clear the virus within six months (WHO, 2008). Hepatitis B accounts for 60-80% of primary liver cancer worldwide, raising health costs and increasing disease burden. The vaccine itself is expensive and had been neglected by many developing countries for years due to its cost - US$150 for all three doses - and the relative invisibility of the disease. The clinical efficacy of this vaccine ranges from 90% in adults to 95% in infants. However, the Vaccine Fund has been making it available over the last several years to some of the poorest countries in the world. By the end of 2001, 142 countries were using Hepatitis B vaccines in routine infant immunization schedules. In 2002, the Vaccine Fund increased its support into 40 more countries. In 2009, 92% of countries had integrated the Hepatitis B vaccine into their routine infant immunization schedules (WHO, 2010).
In 2009, WHO expressed concern over the immunization systems in Western Pacific countries such as Lao People's Democratic Republic, and Papua New Guinea. A larger number of home births in the area make it difficult for immunizations to reach infants. The WHO is calling for more funding and political support from governments in the Western Pacific region (WHO, 2009).
Pneumococcal Vaccine
Pneumococcal disease: The catagory of bacteria that causes Meningitis and pneumonia.
Pneumococcal disease kills one million children under 5 years every year with the global burden of disease being 1.6 million (GAVI, 2009). Licensing and recommendation for the first pneumococcal conjugate vaccine known as PCV7 began in 2000. This vaccine is 60-70% effective in preventing invasive diseases and provides protection against 7 serotypes that are important causes of childhood pneumococcal disease (WHO, 2007). However, it does not include two prevalent disease-causing serotypes, types 1 and 5, which are the most significant for developing countries. According to GAVI, as of 2009, there were two vaccines available: the 7 valent conjugar vaccine, Prevnar and the 23-valent unconjugated polysaccharide vaccine.
On February 24, 2010 a new vaccine, PCV13, was approved by the FDA for use and will replace the PCV7 vaccine as the recommended vaccine for children when it becomes available (NNii, 2010). The continuing effort to improve immunization coverage is a testament to how populations are impacted by ever-changing advancements in the vaccine field.
Bacillus Calmette-Guérin (BCG)
Tuberculosis: Tuberculosis (TB) is a common, and in many cases lethal, infectious disease, which typically attacks the lungs, but is capable of affecting other parts of the body. One third of the world's population is thought to have been infected with tuberculosis, with new infections occurring in about 1% of the population each year. In 2010, there were an estimated 8.8 million new cases and 1.5 million associated deaths, mostly occurring in developing nations. More people in the developing world contract tuberculosis because of compromised immunity, largely due to high rates of HIV/AIDS infection. (WHO,2011)
As of 2011, the only currently available vaccine for Tuberculosis is Bacillus Calmette-Guérin (BCG) which, although effective against disseminated disease in childhood, confers inconsistent protection against contracting pulmonary TB (McShane, 2011). Nevertheless, it is the most widely used vaccine worldwide, with more than 90% of all children receiving the vaccine. However, the immunity it induces decreases after about ten years.(Lawn, 2011)
Pertussis
Pertussis: Also known as Whooping Cough. A highly contagious bacterial disease. Prevention by vaccination is of primary importance given the seriousness of the disease in children. Although treatment is of little direct benefit to the person infected, antibiotics are recommended because they shorten the duration of infectiousness. It is estimated that the disease currently affects 48.5 million people yearly, resulting in nearly 295,000 deaths. (Bettiol et al, 2012)
Pertussis vaccines are effective (Zhang, 2012), routinely recommended by the World Health Organization and the Center for Disease Control and Prevention, and saved over half a million lives in 2002. (WHO, 2011) However, it is important to note that immunization against pertussis does not confer lifelong immunity, as a 2011 study by the CDC indicated that the duration of protection may only last three to six years. This covers childhood, which is the time of greatest exposure and greatest risk of death from pertussis.(Versteegh, 2005)
For children, the immunizations are commonly given in combination with immunizations against tetanus, diphtheria, polio (DPT/DTP3) and haemophilus influenzae type B (Hib) at ages two, four, six, and 15-18 months.(South African Vaccination and Immunisation Center)
Diptheria
Diptheria: An infectious upper respiratory tract illness, spread by direct physical contact or breathing the aerosolized secretions of infected individuals. (Public Health Agency Canada, 2012)
The diphtheria-pertussis-tetanus (DPT) vaccine is recommended for all school-age children and boosters of the vaccine are recommended for adults, since the benefits of the vaccine decrease with age without constant re-exposure; they are particularly recommended for those traveling to areas where the disease has not been eradicated. (WHO, 2012)
Rotavirus
Hib (Haemophilus influenzae (type b)) Vaccine
The year 1987 marked the release of the first Hib conjugate vaccine (NNii, 2010). The introduction of this vaccine dramatically decreased the incidence of Hib in the developed world. But due to high costs of obtaining and administering the vaccines and a lack of information regarding the burden of disease, the developing world did not initially see the same decrease. The Gambia started a study in 1997 by initiating routine immunizations that showed a reduction of incidence rates among under-ones go from 200 cases per 100,000 to no new cases by 2002.
Efficacy of two doses against Hib disease was 94% (Adegbola, 2005). Success in The Gambia, despite interruptions in vaccine supply, has helped initiate routine vaccination programs in other parts of the developing world (GAVI, 2005). For example, the Journal of the American Medical Association (JAMA) published that three years after the introduction of routine Hib vaccinations among infants in Kenya greatly reduced persistent Hib rates by 88% (The Hib Initiative, Online, 2006). As of 2005, 101 countries include the Hib vaccine as part of their national routine immunization schedule (WHO, 2007). However, as reported by the WHO in 2008, only 28% of the global population has received this vaccine (WHO, 2009).
Meningococcal Vaccine