Literature Review of Polio Vaccines

2010d). Immunization is a proven tool for controlling life-threatening diseases and is estimated to forestall over 2 million deaths annually (WHO, 2010d). Smith et al (2004) stressed that immunizations have averted vaccine-preventable diseases effectively and have reduced their fear in many societies. Greenwood et al (2007) further affirmed that immunization is a major means by which infections may be controlled and in some cases, eradicated. Due to its importance, Sutter & Cochi (2008) stated that immunizations are a critical part of public health practice.

Furthermore, Greenwood et al (2007) stated that the main rationale behind immunization is to produce a degree of resistance sufficient to prevent a clinical attack of the natural infection to the recipients without any harm and to prevent the spread of infection to susceptible individuals in a community.

Economically, immunization is the most cost-effective health intervention with proven strategies that makes it accessible to vulnerable and hard-to-reach populations of a society (i.e. populations with the lowest health status) (WHO, 2010d). Furthermore, it has clearly defined target groups and it can be achieved through outreach activities (Smith et al, 2004). In addition, there is both a personal gain from being immunized and a public health benefit to the population, for instance through the achievement of herd immunity in a community (Greenwood et al, 2007). Herd immunity on the other hand was explained by Mackett & Williamson (1995) as the level in which natural transmission of a particular infection that spreads from person-to-person is inhibited because most people in a community are immune. However, Greenwood et al, (2007) pointed out that herd immunity operates only for infections that spread from person-to-person.

Immunization can be attained through various techniques, most commonly vaccination (Miller, 2002). Vaccination on the other hand is the administration of antigenic materials (vaccines) to produce immunity against a disease and vaccines can ameliorate the effects of infection by pathogens and there is strong evidence for the efficacy of influenza, measles-mumps-rubella (MMR), polio, smallpox and chickenpox vaccines among others (Fiore et al, 2009; Chang et al, 2009).

The word vaccination was first used by Edward Jenner in 1976 (Dunn, 1996) and Louis Pasteur (a French chemist and microbiologist) who furthered the concept through a pioneering work in microbiology by developing a rabies vaccine now termed an antitoxin, which lead to a wide acceptance of vaccines and passage of compulsory vaccination laws in many countries in the 19th century (Stern and Markel, 2005).

Stern and Markel (2005) further pointed out that the 20th century marked the introduction of several effective vaccines which include; diphtheria, MMR, and polio vaccines. However, in terms of effectiveness, Grammatikos et al (2009) argued that vaccines do not guarantee complete protection from a disease and stated some of the reasons to be failure of the host’s immune system to respond adequately to the vaccine due to compromised immunity from either age, HIV infection, diabetes, steroid use or other factors alike or even lack of β-cells in the immune system. (A β-cell is defined by Albert et al (2002) as a cell capable of generating antibodies to antigens). However, Greenwood et al (2007) counter-argued that although the degree of resistance conferred may not protect against an overwhelming challenge, the exposure may help boost the recipient’s immunity.

There are several types of vaccines currently in use ranging from inactivated (killed) vaccines (for example influenza vaccine, Hepatitis A vaccine, rabies vaccine, and polio vaccine); live attenuated vaccines (example MMR, Bacillus Calmette-Guѐrin [BCG] for tuberculosis, and oral polio vaccine); toxoids (for example tetanus and diphtheria vaccines); subunit vaccines (for example Haemophilus influenzae type B vaccine); to experimental vaccines such as that of valley fever, stomatitis, and atopic dermatitis (Cates, 2000).

In relation to this, polio vaccine (which is the basis of this research) will be described in more detail in the subsequent heading.


Polio vaccine is described by Monsoon & Schoenstadt (2010) as a remedy that is administered to prevent polio which is highly effective in producing immunity to polio virus and protection from paralytic poliomyelitis, because approximately 90% or more recipients of the vaccine develop protective antibodies to all three poliovirus types after two doses and at least 99% become immune after three doses. The Global Polio Eradication Initiative (G.P.E.I) (2010a) reiterated that the development of polio vaccines was one of the foremost medical discoveries of the 20th century.

Two types of polio vaccines are available which include; a live attenuated or weakened oral polio vaccine (OPV) commonly called the Sabin vaccine which is administered orally, and an inactivated (killed) polio vaccine (IPV) commonly called the Salk vaccine which is administered via injection by a trained health worker (Sutter & Cochi, 2008; G.P.E.I, 2010a).

It is imperative to understand the individual types of polio vaccines and how they work alongside their merits and demerits.

2.1.1 Oral Polio Vaccine (OPV)

The efficacy of the OPV is bilateral in that it produces antibodies in the blood referred to as humoral or serum immunity to all the three types of polioviruses and it also elicits local immune response in the mucous membrane of the intestines (G.P.E.I, 2010a). Torok et al (2009) described the mucous membrane of the intestines as the primary site of poliovirus infection. G.P.E.I (2010a) reiterated that the disruption of person-to-person transmission is probably the main reason why OPV is opted for mass immunization campaigns.

Advantages of OPV include the following; it is administered orally, it can be given by volunteers – not necessarily health workers, it doesn’t require sterile injection equipments which is contrary to most vaccines, it is cost-effective because it is relatively inexpensive and at the time of writing it costs 8 US cents equivalent to 5 pence a dose (G.P.E.I, 2010a) (cost-effectiveness, considerations of need, efficacy, safety and ease of administration are major factors that influence governments to purchase large quantities of vaccines during National Immunization Days {Greenwood et al, 2007}). The above mentioned advantages make OPV the vaccine of choice for polio eradication which would not be feasible with IPV. (G.P.E.I, 2010a)

The disadvantage of OPV on the other hand was argued by Cono & Alexander (2002) that although OPV is safe and effective, it induces vaccine associated polio paralysis (VAPP) in either the vaccinated child or close contact in rare cases. G.P.E.I (2010b) further explained VAPP to be caused as a result of live attenuated poliovirus strains contained in the OPV while Cono & Alexander (2002) mentioned immune deficiency of the recipients to be among the causes. G.P.E.I (2010b) stressed that VAPP is familiar and accepted by most public health programmes across the globe but alleged that without OPV hundreds of thousands of children would be crippled annually. WHO (1998) stated that the emergence of VAPP led to combined immunization schedules using both OPV and IPV in many countries where the risk of wild poliovirus cases were low.

G.P.E.I (2010b) added further on the disadvantages of OPV by stating that in rare cases a strain of poliovirus in OPV may genetically change and circulate within a population leading to a vaccine-derived poliovirus (VDPV). Brooks et al (2007) defined vaccine-derived poliovirus (VDPV) as live, attenuated (weakened) strains of the virus contained in OPV which have been modified and reverted (i.e. reacquired original features) to a form that can cause paralysis in humans with the capacity for sustained circulation. VDPV are of three types: circulating vaccine-derived polioviruses (cVDPV), which are associated with person-to-person transmission and considered to be circulated in the environment; immunodeficiency related vaccine-derived polioviruses (iVDPV), which are isolated from immune-compromised patients who had prolonged infections after exposure to OPV, and ambiguous vaccine-derived polioviruses (aVDPV) which are isolated from a single immune-competent paralytic poliomyelitis patient with or without additional isolates from close contacts, healthy individuals, or the environment in the absence of paralytic cases. (G.P.E.I 2010b)

Sutter & Cochi (2008) further outlined that cVDPV have caused outbreaks in Indonesia (2005), China (2004), Egypt (1988-1993), Hispaniola (2000-2001), Madagascar (2002), and the Philippines (2001) but maintained however that extensive control efforts relying on massive use of OPV have controlled these outbreaks.

2.1.2 Inactivated Polio Vaccine (IPV)

IPV is administered via injection and it provides immunity by producing antibodies in the blood (humoral or serum immunity). This form of immunity prevents the spread of poliovirus to the central nervous system (G.P.E.I, 2010a). However, it induces only very low levels of immunity to poliovirus locally inside the gut. As a result, it provides individual protection against polio paralysis but, unlike OPV, it cannot prevent the spread of wild poliovirus. (Nester et al, 2009)

Advantages of IPV include; IPV is not a live vaccine – the poliovirus is inactivated and immunization with IPV carries no risk of vaccine associated polio paralysis (Nester et al, 2009). Immunization with IPV triggers an excellent response of the immune system in most IPV recipients (Cono & Alexander, 2002).

On the other hand, the disadvantages of IPV as stated by G.P.E.I (2010a) is that unlike OPV, IPV confers only very little immunity in the intestinal tract. Cono & Alexander (2002) affirmed that when a person immunized with IPV is infected with wild poliovirus, the viruses can still multiply inside the intestines and be shed in stools risking continued circulation. For this reason, OPV is the vaccine of choice wherever a polio outbreak needs to be contained even in countries which rely exclusively on IPV for their routine immunization (G.P.E.I, 2010a).

Other disadvantages of IPV include the price (over five times that of OPV), the cost of the syringe, and the need for trained health workers to administer the vaccine using sterile injection procedures also adds up to the expenses. (Pearce, 2004)

Having outlined the types of polio vaccines, alongside their merits and demerits, both vaccines are effective towards interrupting the disease both in the developed and developing countries. Furthermore, the developed countries are capable of using inactivated polio vaccine due to its high cost and low risk of vaccine associated polio paralysis or circulating vaccine derived poliovirus infections. However, oral polio vaccine is still the vaccine of choice in controlling outbreaks and in polio endemic countries such as Nigeria; therefore there is need for a research towards improving oral polio vaccine.


In this section, the author seeks to explore briefly immunization practice in developed countries but with restriction to the UK and emphasis on polio immunization. Reason for this is to present to the reader the inequalities that exist between the developed and the developing countries with respect to polio immunization uptake hence determining why some parts of the world will be certified polio-free and some regions still suffering the burden of the disease. Pencheon et al (2001) stressed that reducing inequalities and promoting social justice is a foundation of all public health activities around the world.

In the UK, the Department of Health (DoH), Welsh Office, Scottish Home and Health Department, and Department of Health, Social Services, and Public Safety (Northern Ireland) recommend the following primary immunizations in childhood – a course of three doses of diphtheria, tetanus, pertussis, poliomyelitis and Heamophilus influenza type b (Hib) in the first year of life and one dose of MMR vaccine in the second year (Salisbury et al, 2006). As there are no legal powers to force uptake or immunization requirements for entry to school or other communal groups, parents are free to accept or reject immunization for their children. (Bedford &Kendall, 1998)

Immunization uptake rates in the UK are at an all-time high: in March 1996 it was documented that the average uptake among 2-year olds of diphtheria, tetanus and polio vaccines was 96%, of pertussis (whooping cough) 94%, and that of Hib 95%, while 91% of 2-year olds had received MMR vaccine (Communicable Disease Surveillance Center, 1996). However, some areas remain where coverage is lower and the range in uptake between districts is 84-100% for third diphtheria and pertussis, and 75-96% for MMR (Bedford &Kendall, 1998)

Furthermore, Bedford & Kendall (1998) affirmed that these rates have been accompanied by an overall reduction in the incidence of infectious diseases, demonstrating the effectiveness of a successful immunization programme.

Noah (2006) noted that from a public health point of view, maintaining high coverage rates are important in preventing future outbreak of diseases. Notable examples of a decline in vaccine coverage resulting in outbreak of diseases include: whooping cough in the late 1970s and early 1980s in England and Wales (Communicable Disease Surveillance Center, 1995), diphtheria in the former USSR (Miller et al, 1993), and polio among unvaccinated children in the Netherlands (Oostvoegel et al, 1994).

Egan et al (1992) stated that factors which determine whether a child will be immunized are well established and have been reviewed and these factors fall into three interrelated categories: the enthusiasm and knowledge of health professionals and particularly their knowledge of contraindications to immunization; the organization of the immunization service itself , including factors at the practice level such as accessibility at district level, use of computer databases for evaluating uptake and generating invitations for immunizations; parental factors, including social and family issues and attitudes to severity of disease and safety of vaccines.

Bedford & Kendall (1998) further stressed that these determinants of immunization uptake have been identified largely through quantitative studies and research using qualitative methods has enabled more detailed exploration of these factors. The authors further commented that the qualitative research methods provide insights into parents’ attitudes, belief and experiences of immunization and the constraints placed particularly on mothers and how these affect acceptance of immunization.

With respect to poliomyelitis, during the early 1950s, there were epidemics of the infection with as many as 8000 annual notifications of paralytic poliomyelitis in the UK (Salisbury et al, 2006). Routine vaccination for polio began in the UK in 1956 using injected inactivated poliomyelitis vaccine (IPV), and this was replaced in 1962 with oral, live attenuated polio vaccine (OPV) (Mayon-White & Moreton, 1997). Notifications of paralytic poliomyelitis however dropped from nearly 4000 in 1955 to 257 in 1960, between 1974 and 1978 35 cases were reported, and since then there have been an average of three cases per year, two of which are vaccine associated cases (Salisbury et al, 2006).

Mayon-White & Moreton (1997) observed that a few cases of poliomyelitis in the UK are due to infection acquired abroad; and overseas travel to countries which are polio endemic has been an indication for the necessity of a booster dose. For instance, Salisbury et al (2006) stressed that following a resurgence of polio in Nigeria, poliomyelitis was reported during 2005 and 2006 from several countries that have been polio-free. In these countries, intensive efforts to interrupt transmission and to establish control are being undertaken, and the risk of importation to the UK is still considered low.

The recommended national immunization schedule in the UK is categorized into: primary immunization, secondary immunization, and tertiary immunization. (Salisbury et al, 2006)

The primary immunization is further explained by Greenwood et al (2007) to be comprised of the following stages. At birth, the Hepatitis B vaccine is for children born to women who are carriers of the Hepatitis B virus, and if the mother is carrying the Hepatitis B ‘e’ antigen, the baby should have an additional single dose of Hepatitis B immunoglobulin, which should be given in the opposite thigh at birth. Two more doses of the vaccine are required at 1 and 6 months of age; Bacillus Calmette-Guѐrin (BCG) vaccine for some babies of immigrant families, and those in house-hold contact with tuberculosis; Polio, DTP and Hib vaccine at 2 months, 3 months, and 4 months; and measles, mumps and rubella (MMR) at 12-15 months.

The secondary immunization schedule is usually a booster dose of polio, tetanus and diphtheria, and MMR at 4-5 years and is termed preschool immunization. In addition, it provides the chance to catch up primary immunization to any child who has missed out on earlier vaccinations. (Greenwood et al, 2007)

The tertiary immunization is by administering BCG at 10-14 years of age and polio, tetanus and diphtheria at 13-18 years of age (Greenwood et al, 2007). In addition, the authors highlighted that all children should be immunized even if they are outside the recommended ages and that no opportunity to immunize should be missed as there is no upper age limit for immunization, and children attending for their school-leaving immunizations should have their immunization status checked, and be offered MMR if appropriate.

From the UK immunization schedule explained above, it can be noted that polio vaccine is administered at 1, 4-5, and 13-18 years of age. This could be due to the nature of the poliovirus and fear of wearing away of the immunity as the recipients are ageing. Burns (2007) affirmed that a high rate of immunization is necessary and antibody levels need to be maintained because evidence has shown that the outcome of exposure to poliovirus is directly related to the level of antibody at the time of exposure in children. The repeated administration of the polio vaccine, parental awareness, and knowledge on the safety of vaccines could be among the factors that induce immunization uptake and possible eradication of polio in the UK. For reference, the UK immunization schedule (Salisbury et al, 2006) is summarized in appendix i.


Nigeria is among the ten countries in the world with vaccine coverage rates below 50% (Hersh, 2005). The country also has the highest prevalence of circulating wild poliovirus in the world (WHO, 2005; Schimmer & Ihekweazu, 2006).

Due to the difficulty faced by some countries in containing polio outbreaks, the World Health Organization (WHO) in 1988 launched the Global Polio Eradication Initiative (G.P.E.I) with the goal of eradicating the disease by the year 2000 (WHO, 1998). In 1989, the World Health Assembly approved a global plan of action for eradicating polio and the WHO Regional Committee for Africa adopted the resolution (Letore, 1998). The polio eradication strategies of WHO Regional Committee for Africa were intensified in 1996 by the establishment of “Kick Polio out of Africa” campaign. This campaign was launched by Nelson Mandela, and aimed to vaccinate 50 million children in 1996 alone. (WHO-Regional Committee for Africa, 1995)

Mass immunization campaigns were boosted by National Immunization Days, improved surveillance, training of local community health workers, and door-to-door campaigns (Organisation of African Unity, 1996; Centers for Disease Control, 2004). The Kick Polio Out of Africa campaign assured functional cold chain systems and continuing education of communities about the importance of routine immunization (WHO-Regional Committee for Africa, 1995). In order to create more awareness on the disease, prominent African football players have been participating in public awareness campaigns since 1997 by distributing posters, conducting radio interviews, and holding public autograph sessions through an alliance with the African Football Confederation (Letore, 1998).

In mid-October 2003, the GPEI launched what was hoped to be the final attack on polio, with a plan to immunize more than 15 million children in west and central Africa. The GPEI had particular concerns about the high prevalence of polio in Nigeria, which accounted for 45% of polio cases worldwide and 80% of cases reported from the African region in 2003 and this high prevalence was attributed to poor vaccine coverage during the previous control campaigns (UNICEF, 2005).

Nigeria’s routine immunization schedule on the other hand requires that infants should be vaccinated with the following vaccines: a dose of Bacillus Calmette-Guerin (BCG) vaccine at birth (or as soon as possible); three doses of Diphtheria, Pertussis and Tetanus (DPT) vaccine at 6, 10 and 14 weeks of age; at least three doses of oral Polio vaccine (OPV) – at birth, and at 6, 10 and 14 weeks of age; and one dose of Measles vaccine at 9 months of age. (UNICEF, 2005)

However, the country’s immunization programmes have been characterized by intermittent failures and successes since the initial introduction in 1956. Immunization programmes were again re-introduced as the Expanded Programme on Immunization (EPI) in 1979 to provide immunization services to children aged 23 months and younger. Following repeated and limited initial success, the immunization programme was re-launched in 1984. (UNICEF, 2005)

The immunization schedule of Nigeria (National Population Commission, 2004) is summarized in appendix ii.

From the above explanation, it can be observed that oral polio vaccine is the vaccine of choice in Nigeria and it is administered in less than one year of age from birth as opposed to the UK where polio vaccine is administered at 1, 4-5, and 13-18 years of age to assure a prolonged immunity to polio. Therefore, it can be stated that there is a wide margin in the administration of polio vaccines in the developing and developed world with Nigeria and the UK as examples and such inequalities have to be addressed for polio to be eradicated in all parts of the world like the once pandemic smallpox disease that was successfully eradicated by immunization.


A theoretical framework helps researchers to organize knowledge and interpret factors and events. It also helps to describe the at-risk and intervention groups, possible determinants, health-promoting behaviors, environmental conditions, and identification of the methods to promote changes in these factors (Bartholomew et al, 2006). Furthermore, Paterson et al (2001) agreed that theoretical framework helps researchers to highlight the scope and define relevant concepts in literature reviews. Hence, the use of a theoretical framework in a literature review cannot be overemphasized.

The theoretical model of behavior change chosen for this research is the health belief model (HBM). HBM was first described by Rosenstock in 1966 and modified by Becker in 1974 and it is one of the widely accepted models in health promotion to explain behavior change (example why people choose to use or not to use health services) (Rosenstock, 1966; Gorin & Arnold, 2006).

For an illustration of the HBM refer to appendix iii, the constituents of the model include:

  • Perceived susceptibility to disease: a person’s subjective perception of the risk of contracting a particular condition or illness
  • Perceived severity: a person’s feelings concerning the seriousness of contracting an illness
  • Perceived benefits: a person’s belief regarding the effectiveness of various actions available to reduce the threat of a disease
  • Perceived barriers: potentially negative aspects of a particular health action
  • Cues to action: these are factors facilitating one to take preventive action (Glanz et al, 2002)

The model has been used in predicting health behaviors such as immunization uptake, delay in seeking medication, mammography and cervical screening, adherence to medication, safe-sex behaviors, and many other health behaviors (Rutter & Quine, 2002). Rosenstock (1974) further stated that HBM’s fundamental principle relies on cognitive expectation which states that human behavior depends mainly on the value that an individual places on a particular goal and on the individual’s estimate of the likelihood that a given action will achieve that goal. In simple terms, people want to avoid illness or recover from an illness and will like to believe that a specific behavior will prevent or enable recovery from an illness.

McKenzie & Smeltzer (2001) affirmed that HBM centers on the hypothesis of three simultaneous occurring factors which are: existence of enough motivation to make health relevant, belief that a person is vulnerable to a serious health threat, and belief that following a particular health recommendation will be beneficial in reducing the perceived threat.

However, one of the main weaknesses of HBM is that it assumes a high degree of rationality (subjecting people to be weighing the good and bad sides of their activities and then modifying their behaviour accordingly) (Katz et al, 2000). Furthermore, Rutter & Quine (2002) added that the model did not specify how different beliefs influence one another or how the explanatory variables combine to influence behavior.

In comparison to other models such as the health action model (HAM) (Tones, 1988), which takes into account some strong motivating forces such as pleasure or pain in investigating why people behave in certain ways, the HBM is also concerned with the psychological determinants of behaviour change (Katz et al, 2000).

In contrast, the stages of change model (SCM) (Prochaska & DiClemente, 1984) premise is that behaviour change takes a series of stages to occur, hence people tend to progress through different stages. However, Bunton et al (1999) argued that the model is mainly descriptive and cannot ascertain how or why people move from one stage to another because change fluctuates and is unpredictable.

In the context of polio immunization uptake, it is unlikely for parents to have their children immunized; when parents feel that vaccines are ineffective, seen as unnecessary or dangerous for infants or children who are not experiencing any health problem or when parents perceive no fear of death by not complying to immunization which in turn enable them lack cues to action. A classical example by Renne (1996) is that of a Rotary Club immunization project in Zaria City, northern Nigeria in March 1995 that was abandoned after the second visit because parents refused to bring their children out for immunization. However, parents are likely to accept their children being immunized if there is the belief that vaccines are effective and perceived benefit outweighs the barriers that inhibit immunization uptake. The uptake behavior in such cases is enhanced by cues to action such as symptoms, mass media campaigns or physician’s advice.


Porta (2008) defined a health determinant as any factor that can cause a change in a health condition and this factor could be physical, biological, social, cultural, economic or behavioral. Dahlgren and Whitehead (1991) further stated that several factors influence health either positively or negatively and these factors include age, sex, hereditary factors, social and community influences, living and working conditions, general socio-economic, cultural and environmental conditions. However, Kavanagh and Bentley (2008) advised that the Dahlgreen and Whitehead model should be treated with caution because the model presentins an exaggerated deterministic, unchanging or constant conception of the factors that influence health. Below are the perceived health determinants of polio eradication in Nigeria.

2.5.1 Political commitment

The Late President of Nigeria, His Excellency Umaru Musa Yar’adua personally committed to ensure that polio was eradicated from Nigeria and in February 2009, the governors of the 36 states collectively signed ‘Abuja commitments to polio eradication’, publicly committing to provide the necessary leadership to eradicate polio. As a result of these efforts, marked improvements in several previously high-risk northern states have been noted (G. P. E. I., 2009b).

WHO (2009c) affirmed the political commitment of Nigerian government by stating that as of 11th November 2009, 1337 cases caused by wild poliovirus (WPV) had been reported to WHO from 23 countries, compared with 1473 cases reported from 16 countries during the same period in 2008 and that the 10% overall decline in cases is primarily the result of a significant drop in the number of cases reported from Nigeria. The WHO (2009c) further stressed that the decline was as a result of progress that has been made in engaging political and traditional leaders, resulting in improvements in reaching children during immunization campaigns and a rapid decline in transmission of all poliovirus types.

However, Last (2005) argued that although the government of Nigeria is committed to eradicating polio, accountability and equity are not ensured by the government because as a country the health infrastructure of the north is not as good as that of the south, hence, the reason why the disease is more prevalent in the northern part of the country than the south and Odutola (2004) highlighted that the divide in health infrastructure could be a limiting factor in the eradication of the disease in the country.

2.5.2 Accessibility and Poor vaccine coverage

Jegede (2007) stated that 50-60% of Nigerians live in the rural areas and poor transportation hinders the coverage of immunizations during mass campaigns. Sutter & Cochi (2008) agree that poor road networks are a problem in Nigeria and therefore pockets of unvaccinated children are left out during mass immunization campaigns. Furthermore, Last (2005) affirmed that much is not done to ensure all children in rural areas are reached during immunization days in the country.

In addition, Mohammed et al (2009) accentuate that some health-workers or vaccination personnel arrive to their designated centers late or with difficulties, hence, disrupting the cold chain of the vaccines and not vaccinating enough individuals.

On the other hand, Obadare (2005) argues that efficient road networks enable mass coverage of immunization in most cities particularly in the South, but Mohammed et al (2009) maintained that most parents experience difficulties in reaching the immunization centers due to poor accessibility. Jegede (2007) supported this fact and emphasized that some individuals have to cross rivers before reaching their designated immunization centers and made reference to Bayelsa State- a riverine area situated in the South-south geo-political zone of Nigeria.

However, Odutola (2004) pointed out that there is a wide divide in terms of immunization uptake in Nigeria and attributed the divide to be not only due to poor accessibility but also to literacy level. The authors acknowledge that for polio to be eradicated in Nigeria, accessibility and education have to be given equal treatment in all geo-political zones of the country.

2.5.3 Literacy level and Education

Two additional goals of the Millennium Development Goals (MDGs) are to directly target the education of women (Todaro & Smith, 2005). Case et al

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