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 Table of Contents  
REVIEW ARTICLE
Year : 2014  |  Volume : 1  |  Issue : 1  |  Page : 15-19

Pneumococcal Infection in Nigeria: Preparing for the vaccine


Infectious Diseases Unit, Department of Medicine, Bayero University and Aminu Kano University Hospital, Kano, Nigeria

Date of Submission16-Aug-2013
Date of Acceptance27-Oct-2013
Date of Web Publication24-Mar-2014

Correspondence Address:
Garba Iliyasu
Infectious Disease Unit, Department of Medicine, Bayero University Kano/ Aminu Kano Teaching Hospital, Kano
Nigeria
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  Abstract 

Background: The Pneumococcus is the most common cause of community-acquired pneumonia (CAP), sporadic bacterial meningitis, and bacteremia worldwide. It is an important public health concern throughout the world with global burden in causing disease and deaths comparable to that of human immunodeficiency virus (HIV), malaria, and tuberculosis. Nigeria accounts for 5% of the total global burden. Many of these morbidity and mortality could be averted with the use of pneumococcal vaccine, which is shown to be highly effective. This review is set out to highlight the burden of pneumococcal infection (PI) in Nigeria, its attendant mortality, antibiotic resistance, and the rational for the need to introduce routine pneumococcal vaccination. Materials and Methods: Relevant literatures were reviewed from medical journals, library search, and internet source. Other relevant websites like Global Alliance for Vaccines and Immunisation (GAVI), WHO were also visited as source for information. The key words employed were: pneumococcal infection, Nigeria, and vaccine. Results: Several studies have shown high burden of PI and high prevalence of antibiotic resistant Pneumococcus in Nigeria. Mortality rate has also been shown to be high and the need for effective implementation of pneumococcal vaccine into routine childhood vaccination program has been underscored. Conclusion: Prevention of pneumococcal disease and death is achievable only if efforts to deliver and implement prevention in regions with the greatest burden of disease are successful. National Primary Healthcare Development Agency (NPHCDA) should introduce either pneumococcal conjugate vaccine (PCV)-13 or PCV-10 through GAVI support to eligible children and at risk adult all over the country. As these new vaccines are introduced, it is imperative that we conduct surveillance to document changes, positive or negative, which occur in disease epidemiology. This entails continuing surveillance pre- and post-vaccine introduction, assessing resistance, changes in invasive PI (IPI), serotypes, and any replacement.

Keywords: Infection, Nigeria, pneumococcus, vaccine


How to cite this article:
Iliyasu G, Habib AG, Borodo MM, Babashani M, Ahmed M. Pneumococcal Infection in Nigeria: Preparing for the vaccine. Sub-Saharan Afr J Med 2014;1:15-9

How to cite this URL:
Iliyasu G, Habib AG, Borodo MM, Babashani M, Ahmed M. Pneumococcal Infection in Nigeria: Preparing for the vaccine. Sub-Saharan Afr J Med [serial online] 2014 [cited 2019 Mar 25];1:15-9. Available from: http://www.ssajm.org/text.asp?2014/1/1/15/129302


  Epidemiology of pneumococcal infection (PI) Top


Streptococcus pneumoniae (the Pneumococcus) has continued to remain an important human pathogen since its initial recognition in the late 1800s. As the leading cause of lower respiratory tract infection, its global burden in causing disease and deaths is comparable to that of human immunodeficiency virus (HIV), malaria, and tuberculosis combined. [1] The 10 countries with the highest burden of PI are in Africa and Asia, and combined together they account for 66% of reported cases worldwide. [2] Nigeria accounts for 5% of the total burden at the third place after India and China. [1] The Pneumococcus is the commonest cause of community-acquired pneumonia (CAP), sporadic meningitis, and bacteremia in children and adults. [3] Worldwide it accounts for 30-70% of CAP cases requiring hospitalization. [4],[5] Studies in Nigeria have shown that PI accounts for 50, 54.5, and 60% of CAP cases in Zaria, Enugu, and Kano, respectively. [6],[7],[8] In a similar report by Ozumba in Enugu, the Pneumococcus has been found to be the single most predominant cause of community-acquired sporadic meningitis. [9] In a recent work in Kano, the pneumococci have been shown to account for 46.4% of CAP, meningitis, and bacteremia. [10]

The World Health Organization (WHO) estimates that 1.6 million people, including up to 1 million children <5 years of age, die of PI annually, [11] with developing countries bearing the greatest burden. [12] Onyemelukwe and Greenwood reported an overall mortality of 39% in the 1980s in Zaria. [13] Previously, a mortality rate of 51 and 48% were reported by Baird and Tugwell in Zaria, respectively. [14],[15] In a recent study by Falade et al., in Ibadan, Nigeria, eight out of the nine cases with culture-proven pneumococcal meningitis died. [16] Prognosis is generally reported to be better for pneumococcal pneumonia, [5] and estimated to be approximately 10% for primary pneumococcal pneumonia, while 10-30% for bacteremic pneumococcal pneumonia. [17]


  Antimicrobial Resistance Top


From the beginning of the antibiotic era to the mid-1970s, the pneumococcus remained uniformly susceptible to all classes of antibiotics that had been active against the organism, with the possible exception of tetracycline. However, in 1977 and 1978 outbreaks of penicillin resistant pneumococci (PRP) were reported in Durban and Johannesburg, South Africa. [18],[19] These organisms appeared to have also acquired genetic material that encoded resistance to other commonly used antibiotics. An alarming increase in infections due to penicillin nonsusceptible pneumococci (PNSP) has been documented in nearly all countries of the world. [20],[21] Benbachir et al., reported that 30.4% of pneumococci as nonsusceptible to penicillin in four African cities (Abidjan, Casablanca, Dakar, and Tunisia). [22] In Kano, Nigeria; 93, 92, 84, 53, and 21% of pneumococci were nonsusceptible to penicillin, cotrimoxazole, tetracycline, and ampicillin, respectively. [23] Penicillin nonsusceptible rates of 18, 29.72, 11.76, and 67% were also reported by different workers in Sokoto, Jos, Lagos, and Maiduguri, respectively. [24],[25],[26],[27] A more recent work by Iliyasu in Kano using E test showed that 28, 8.5, 3.8, 25.8, 96.2, and 18.9% of their pneumococcal isolates to be fully resistance to penicillin (MIC ≥ 2 μg/ml), amoxicillin (MIC ≥ 8 μg/ml), ceftriaxone (MIC ≥ 2 μg/ml), azithromycin (MIC ≥ 16 μg/ml), cotrimoxazole (MIC ≥ 2 μg/ml), and chlorampenicol (MIC ≥ 8 μg/ml), respectively. [10] The rapid emergence of antibiotic resistance is adding to the burden of pneumococcal disease by significantly contributing to the numbers of treatment failures and deaths from this disease.


  Pneumococcal Serotypes Top


Virtually all strains of pneumococci have a polysaccharide capsule, which is the basis for serotyping. [28] Currently, 91 distinct capsular types have been identified, [28] and more than 99% of invasive PIs (IPIs) are caused by these capsulated pneumococci. [29] Globally, about 20 serotypes account for >80% of IPI in all age-groups; 13 serotypes have been implicated in >75% of IPI in children. [11] The dominant serotypes associated with IPI worldwide include 14, 4, 1, 6A, 6B, 3, 8, 7F, 23F, 18C, 19F, and 9V. [30],[31],[32] The predominant serotypes in west Africa are types 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 14, 18, 19, 23, 25, 45, and 46. [33] Serotypes 1 (41%), 3 (22%), 5 (9%), 2 (6%), 18 (6%), 19 (3%), and 41 (4%) were shown to be the predominant serotypes in the 1980's in Zaria and Malumfashi, Nigeria, by Onyemelukwe et al. [13] Recently in Ibadan, Nigeria; serotypes 5, 19F, 4, and 1 predominated out of 11 typed pneumococcal isolates. [16] Different serotypes exhibit differences in attack rates and colonization, case-fatality rates, and clinical expression of disease. [34],[35]

Strategies to combat PIs include adequate antibiotic therapy, and given the emergence of widespread resistance to antibiotics, the use of prophylactic vaccines which are formulated on the basis of the most common capsular serotypes. These are needed urgently in Africa and Asia, which together account for 95% of all pneumococcal deaths. Tetravalent pneumococcal vaccine was first used in 1945; however, it was not widely distributed since its deployment coincided with the discovery of penicillin. The prevailing thought at that time was why worry about a disease so easily controlled by antibiotics? However, the current high prevalence of multidrug resistant strains and the appreciable morbidity and mortality associated with invasive infections make vaccination more attractive, particularly in patients at increased risk. For effective introduction of pneumococcal vaccine in any geographic location, an updated knowledge regarding the prevalence of the serotypes circulating is necessary, to date this adequate data is still lacking in Nigeria. Vaccines representing a subgroup of highly prevalent types have been formulated in most developed countries. However, the distribution of serotypes responsible for pneumococcal disease differs across the world. The pneumococcal polysaccharide vaccine (PPV) which includes 23 purified capsular polysaccharide antigens (serotypes 1, 2, 3, 4, 5, 6B, 7F, 8, 9N, 9V, 10A, 11A, 12F, 14, 15B, 17F, 18C, 19A, 19F, 20, 22F, 23F, and 33F) was introduced in 1983. [36] The pentavalent pneumococcal conjugate vaccine (PVC)7 is a major step forward for vaccination in children under the age of 2 years, since the polysaccharides vaccines are not immunogenic in this high-risk age group. [37] PCV7 contains seven capsular polysaccharides; 4, 9V, 14, 19F, 23F, oligosaccharide of 18C, and 4 μg of 6B, each conjugated to inactivated diphtheria toxin. [38] More recently serotypes 10- and 13-valent vaccine were introduced. In most series, more than 80% of IPIs were due to serotypes encompassed in the 23-valent PPV, and 40-70% were due to serotypes included in the PCV7. [29],[39] In Nigeria, Falade and coworkers found that all the 11 serotyped isolates in their study are contained in the 10- and 13-valent PCV, while serotypes 19F and 4, which constitute about 55% of the isolates being contained in the 7-valent vaccine. [16]

Pneumococcal vaccination has been shown to have an overall protective efficacy against IPI of 54-64%. [40],[41],[42] It is less effective in immunocompromised patients, [43],[44] preventing non-bacteremic pneumonia [40],[45] or noninvasive infections. [46] In Gambia, Cutts et al., reported 77% reduction in vaccine serotype associated IPI with 50% reduction in overall culture-proven IPI and an absolute reduction of 7.4 deaths per 1,000 vaccinated children in a randomized double-blind control trial. [47] Vaccinating children has indirectly protected non-immunized members of the community, including the elderly and non-vaccinated children by reducing pneumococcal transmission. [48]

With the introduction of universal conjugate vaccination in several industrialized countries, the clinical epidemiology of IPI has changed dramatically, and ''replacement'' disease caused by non-vaccine serotypes has caused concern. [49],[50] In a population-based cohort study by Harboe et al., results indicated that serotypes recently identified as potential (re-)emerging serotypes, such as serotype 3 and 19A, are associated with relatively high mortality in individuals aged 5 years and older compared with serotype 1 (the most common serotype) and other serotypes included in PCV7. [51]

Given the multitude of new vaccines available for introduction into national immunization programs, health economic modeling of various immunization plans is becoming increasingly important in informing decisions on health policy. It is estimated that in the 72 Global Alliance for Vaccines and Immunisation (GAVI)-eligible countries, without pneumococcal vaccination, there would be 3.79 million deaths of children aged 3-29 months yearly. Pneumococcal vaccination was projected to prevent 262,000 of these deaths (7%) and avert 8.34 million disability-adjusted life years (DALYs) annually if delivered at coverage rates similar to those for diphtheria-tetanus-pertussis (DTP3). In India, Pakistan, Ethiopia, Tanzania, and Nigeria; 139,000 deaths could be averted, accounting for 53% of all deaths that could be averted in all GAVI-eligible countries. [52] At a vaccine cost of $5/dose it was projected to be highly cost-effective in 68 of 72 countries (including Nigeria). [52]

Prevention of pneumococcal disease and death is achievable only if efforts to deliver and implement prevention in regions with the greatest burden of disease are successful. Currently, PV is not a component of routine immunization in Nigeria. However, with regards to feasibility and planning for PCV introduction in Nigeria, we suggest that National Primary Healthcare Development Agency (NPHCDA) should introduce either PCV-13 or PCV-10 through GAVI to support eligible children all over the country. Furthermore, it might be started across the six health zones in a scalable manner; potentially up to 1 million children in each of the six health zones may be targeted. Vaccinating high risk adults with certain background diseases (chronic liver disease, chronic bronchopulmonary disease, diabetes, renal disease, HIV/acquired immunodeficiency syndrome (AIDS), alcoholism, sickle cell disease, pneumoconioses, etc.) with PPV should also be strengthened.

As these new vaccines are introduced, it is imperative that we conduct surveillance to document changes, positive or negative, which occur in disease epidemiology. This entails continuing surveillance pre- and post-vaccine introduction, assessing resistance states, changes in IPI incidences, responsible serotypes, and any replacement. It should commence with a baseline survey covering the whole country with subsequent periodic serotype and antimicrobial resistance surveillance. Prevention of pneumococcal disease will greatly accelerate progress towards Millennium Development Goal (MDG) [4],[37],[38] which aims to reduce mortality in children younger than 5 years by two-thirds by 2015.

 
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