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American Journal of Public Health Research
DOI: 10.12691/ajphr-1-1-3

The Implementation of a Tele-Homecare System with Service Oriented Architecture and HL7 Message Transmission Standard
Ching-Sung Wang

American Journal of Medical and Biological Research
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The Influence of Ethanol on Pyruvate Kinases Activity in Vivo, in Vitro, in Silico
Lelevich Sergey Vladimirovich, Khrustalev Vladislav Victorovich, Barkovsky Eugene Victorovich, Shedogubova Tatyana Aleksandrovna

American Journal of Medical Sciences and Medicine
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Clinical and Histological Features in Wegener Granulomatosis
Li Cavoli Gioacchino, Passantino Rita, Bono Luisa, Tortorici Calogera, Ferrantelli Angelo, Giammarresi Carlo, Rotolo Ugo

American Journal of Infectious Diseases and Microbiology
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The Curse of Lymphatic Filariasis: Would the Continual Use of Diethylcarbamazine Eliminate this Scourge in Papua New Guinea?
Anne Lanham, Lillian Mwanri

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Dear Label_Name,

Greetings! I hope you are well.

I am writing on behalf of an international publishing house, Science and Education Publishing, USA (http://www.sciepub.com).

Science and Education Publishing (SciEP) is a multidisciplinary open access publisher of Journals covering the fields of Science, Technology and Medicine. All SciEP publications are subject to high-quality peer review, editorial and production processes and are freely available online.

Welcome to the April, 2013 edition of SciEP newsletter, providing monthly summaries of articles on science & education related topics of interest to scientist and professionals. The mission of our journals is to provide an open access forum for publishing new findings on issues pertinent to scientific and academic field. We also invite you to submit original research papers, review articles, short reports, or case studies are considered for publication in our Multidisciplinary Journals.

American Journal of Public Health Research
DOI: 10.12691/ajphr-1-1-3

The Implementation of a Tele-Homecare System with Service Oriented Architecture and HL7 Message Transmission Standard
Ching-Sung Wang

American Journal of Medical and Biological Research
DOI: 10.12691/ajmbr-1-1-2

The Influence of Ethanol on Pyruvate Kinases Activity in Vivo, in Vitro, in Silico
Lelevich Sergey Vladimirovich, Khrustalev Vladislav Victorovich, Barkovsky Eugene Victorovich, Shedogubova Tatyana Aleksandrovna

American Journal of Medical Sciences and Medicine
DOI: 10.12691/ajmsm-1-1-1

Clinical and Histological Features in Wegener Granulomatosis
Li Cavoli Gioacchino, Passantino Rita, Bono Luisa, Tortorici Calogera, Ferrantelli Angelo, Giammarresi Carlo, Rotolo Ugo

American Journal of Infectious Diseases and Microbiology
DOI: 10.12691/ajidm-1-1-2

The Curse of Lymphatic Filariasis: Would the Continual Use of Diethylcarbamazine Eliminate this Scourge in Papua New Guinea?
Anne Lanham, Lillian Mwanri

We have released issues of some journals on February 2013.
American Journal of Public Health Research
American Journal of Medical Sciences and Medicine
American Journal of Medical and Biological Research
American Journal of Pharmacological Sciences
American Journal of Clinical Medicine Research
American Journal of Nursing Research
American Journal of Cancer Prevention
American Journal of Medicine Studies
American Journal of Infectious Diseases and Microbiology
American Journal of Cardiovascular Disease Research
American Journal of Biomedical Research
American Journal of Mechanical Engineering
American Journal of Microbiological Research
Journal of Preventive Medicine
American Journal of Food and Nutrition
American Journal of Hypertension Research
American Journal of Sports Science and Medicine
Journal of Cancer Research and Treatment
American Journal of Zoological Research
Journal of Biomedical Engineering and Technology
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Biomedical Science and Engineering

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Vaccination Coverage, Discrepancies and Trends in Measles Epidemics in the North West Region of Cameroon

Wasu Chrispus Nchandone, Ginette Claude Mireille Kalla, Njamnshi Alfred Nkongnyu, Same Ekobo Albert, Assob Jules Clement Nguedia*

Faculty of Medicine and Pharmaceutical Sciences, University of Douala Cameroon

Abstract: Background: Measles, because of its burden of morbidity and mortality, is one of the most important diseases targeted by immunization. Caused by a virus, it is very contagious and therefore requires vaccination during the first year to avoid serious complications. Global death toll was over 140,000 persons in 2018. In recent years, measles cases have increased and outbreaks recorded due to declining vaccination coverage worldwide. Thus, countries that were previously declared measles-free and preparing to eliminate measles are still recording cases. This increase in measles incidence has also been observed in the North West region of Cameroon and outbreak surveys have indicated low vaccination coverage. Objective: Determine vaccination coverage and gaps for BCG, Pentavalent and Measles vaccines; as well as measles epidemic trends in the North West region of Cameroon. Methods: This was a cross-sectional, descriptive study with retrospective collection of routine vaccination records and measles epidemic census reports that were carried out at the Regional Delegation of Public Health from 2009 to 2015. The data collected using a structured form were: data from immunization coverage records; age groups and time periods of measles cases reported during measles outbreaks. Results: Overall vaccination coverage for BCG, Pentavalent and measles was low, ranging from 55.5% to 74.7%; with a high dropout rate of more than 15.4% between the third dose of the pentavalent vaccine and the measles vaccine in 2010. The measles vaccine recorded its highest vaccination coverage of 67.9% in 2011. Measles outbreaks have been noted to mainly affect children between the ages of 5 and 15 and occur from January to March with a peak in February. Conclusion: Overall immunization coverage is low with high dropout rates between vaccines. The highest immunization coverage for the measles vaccine was 67.9%; with variations over time. Measles epidemics in the North-West region occur from January to March, with peaks in February and mainly concern children aged between 5 and 15 years.

Keywords: measles, vaccine, coverage, discrepancies, epidemics and trends

Received June 10, 2022; Revised July 14, 2022; Accepted July 24, 2022

Citation: Wasu Chrispus Nchandone, Ginette Claude Mireille Kalla, Njamnshi Alfred Nkongnyu, Same Ekobo Albert, Assob Jules Clement Nguedia, Vaccination Coverage, Discrepancies and Trends in Measles Epidemics in the North West Region of Cameroon. American Journal of Epidemiology and Infectious Disease, 10 (2). 59-67. January 2022. doi:10.12691/ajeid-10-2-3

1. Introduction

Measles is the most important disease among the ones targeted by the Expanded Programme on Immunization (EPI), and requires immunization during the first year of age to avoid complications [1,2,3,4]. Measles is caused by a virus of the myxoviruses group and is highly contagious and associated with high morbidity and mortality [1,5]. Measles remain a global public health problem with over 20 million cases occurring annually [6,7], and involves substantial health care cost for the society [8,9]. According to the World Health Organization (WHO) and the Centers for Disease Control and prevention (CDC), the global death toll for measles stood at 140,000 people in 2018, most of which were children under 5 years of age [10]. Measles is highly preventable and prevention is ensured by the use of vaccination [1,11], which is administered alongside other vaccines of the EPI programme that started in 1976 in Cameroon [12], following the EPI launch by the WHO in 1974 [13,14]. Measles vaccine is equally effective in preventing its spread even during an outbreak response [15]. In recent years, measles cases have increased, especially during epidemics, due to declining vaccination coverage worldwide. As a result, countries that were previously declared measles-free, preparing for measles elimination, have seen new cases [1,16]. For the same reason, despite the availability of an effective and safe vaccine, provided free of charge, measles epidemics continue to occur even in the North West Region of Cameroon [17]. A measles epidemic is confirmed with 3 or more measles IgM positive cases in a health facility or district in one month [18]. Following this definition, measles epidemics were declared in the North West Region in 2012, 2013, 2014 and 2015. A situation which could have been averted by the achievement of a population-based herd immunity with a vaccination coverage of 92-95% of children [19]. Therefore, vaccination coverage below this rate could have favored the onset of the measles epidemic in the North-West region, despite the efforts to reduce the incidence of measles recorded in the region [20]. A study conducted in the Far North Region of Cameroon, more precisely in Maroua, blamed a long lasting measles epidemic on low vaccination coverage [21]. In the same light, an outbreak investigation following the occurrence of a measles epidemic in Benakuma Health District of the NWR, still pointed to low vaccination coverage [17]. Hence our work entitled: “Vaccination Coverage, Discrepancies and Trends in Measles Epidemics in the North West Region of Cameroon”.

2. Materials and Methods

2.1. The Expanded Program Immunization (EPI) in Cameroon

In Cameroon, the EPI program started in 1976 as a pilot project coordinated by the Organization for the Coordination of the Control of Endemic Diseases in Central Africa (OCEAC), and later became scaled up and went operational in all regions of the country in 1982. This program then later became an integral part of the minimum package of activity (MPA) for health services, following the Declaration of the Reorientation of Primary Health Care (PHC). The program started off with four vaccines, targeting Tuberculosis; Poliomyelitis; Diphtheria, Tetanus and Pertussis; and Measles. This program progressively witnessed the addition of new vaccines, targeting vaccine preventable diseases such as: Yellow fever in 1988 (given with measles vaccine); Hepatitis B in 1992; Haemophilus influenza type b in 1998. Up to 2015, the EPI program in Cameroon covered all 189 health districts and all the health areas in the national territory including the 10 health districts and health areas targeted by this study. The program up to this date was delivering the following vaccines for childhood immunization: BCG, Poliomyelitis, Rotaviruses, Pentavalent, Pneumococcal conjugate vaccine, Injectable Poliomyelitis vaccine, Tetanus toxoid, Measles and Yellow fever vaccines. Vaccines are delivered at fixed vaccination centers in health facilities and covers the population within a radius of 5 km; Outreach posts within a distance of 5 to 10 km from the health facility and at mobile strategy covering the population within a distance of over 10 to 15 km from the health facility. The mobile strategy would require staff to travel and work the following day at these sites. The administration of vaccines at fixed vaccination centers take place on daily basis (with available refrigerators), while at the outreach posts occurs on a once monthly basis, same as for the mobile strategy. The vaccination strategies of outreach and mobile strategies requires extra positive cold chain equipment (capable of maintaining temperatures between +2 to +8 degree centigrade), such as vaccine carriers and cold boxes as well as transportation equipment like vehicles, motor cycles, boats and horses. It requires extra finances as well as personnel for the administration of vaccines to the population following their prior notification of the schedules dates and time. The number of vaccination sites and types of vaccination strategy of a given health area would depend on the geographic accessibility of the population and the population density, to ensure an effective population coverage with vaccination services. It is a mandatory responsibility of every health area head to ensure the necessary vaccination centers are created and rendered functional, under the supervision of the health district medical officer, who ensured all were in place as needed and functional.

Up till 2015, measles vaccine in Cameroon was administered as a single dose at the age of 9 months in routine immunization. In the situation of a measles outbreak, children at the age of 6 months were vaccinated to limit the propagation of the virus in the population and the vaccine is repeated at the age of 9 months. The measles vaccine given at the age of 6 months is feared of being rendered ineffective due to interaction with maternal antibodies transplacentally transmitted to the child. This explains why the vaccine is repeated at the age of 9 months, to ensure effective immunization. Other opportunities for measles vaccination comes up during Supplementary Immunization Activities (SIA), which offers another opportunity for children missed out during routine vaccination activities or those vaccinated but who failed to develop immunity against the measles virus.

2.2. Measles Cases, Diagnosis and Reporting System

Measles cases were reported to the health system in routine measles case-based surveillance system, which entails suspecting, investigating (collection of biological samples) and reporting of measles cases for confirmation by the WHO certified laboratory of Centre Pasteur du Cameroon in Yaounde (CPC). Here, a suspected measles case was considered to be any person with generalized maculo-papular rash and fever plus one of either cough or coryza (runny nose) or conjunctivitis (red eyes); Or any person in whom a clinician suspects measles. A confirmed measles case on the other hand is a suspected case with positive IgM antibody on laboratory investigation or who was epidemiologically linked to a confirmed case in an outbreak. The case definition of a suspected case of measles is made simple at the community level to encourage more notification from the community and is “any person with rash and fever”, should be referred to a health facility. Therefore, the health personnel and community members’ responsibility here was mainly to suspect a measles cases while confirmation of measles was the responsibility of the WHO certified laboratory (CPC). The reporting of these measles cases were done on weekly basis by reporting in the weekly epidemiological form and summarized at the end of the month in the monthly epidemiological form and routine EPI monthly reporting form. On the other hand, reporting of measles cases during an epidemic was done through line listing reports of the cases as they come up on daily basis, during the epidemic. The reporting chain consisted forwarding this data from the community level to the health facility, then, to the Districts health services, to the Regional delegation and finally to the Central level (Ministry of Public Health), who then, shares the data with the International partner organizations like the WHO and the United Nations International Children’s Emergency Fund – UNICEF.

2.3. Operational Definitions

Measles epidemic: A measles epidemic is confirmed in a health district when 3 cases of positive IgM antibodies are confirmed within 28 days or one month.

Trends: This refers to the general direction in the occurrence of measles, in terms of age group and seasonality.

2.4. Study Design

The study design was quantitative, cross-sectional with retrospective collection.

2.5. Study Setting

This study was conducted at the RDPH for the North West Region. The RDPH is the intermediary level in the health system where health policies are elaborated for implementation at the District level. It is also here that health data are submitted from the health districts for onward transmission to the Central level and also shared with health partners at the international level. This review was done at the RDPH for the North West Region, at the EPI data manager’s office, where data are archived.

2.6. Study Duration and Period

The duration of the study was two months from March to April 2020, and the study covered the period from 2009 to 2015 (7 years).

2.7. Target Population

This involved the EPI population of 0-5 years reported in routine vaccination reports, and every other person reported for measles in routine measles surveillance reports and Line listing reports for measles epidemics. Here, a particular number was not calculated as a target since we did not know the number of children reported in the vaccination, surveillance and line listing reports, as this study was a record review. Therefore, every individual reported in the study area during the study period was included in the data collected. In calculating the vaccination coverage, the population estimates for children 0 to 5 years provide at beginning of the year, was used as reported in the monthly vaccination reports of each study area.

2.8. Vaccination Coverage and Dropout Rates

The vaccination coverage rate is calculated as follows:

Vaccination coverage rate (for a particular vaccine) = number receiving all doses ÷ number in the target population x 100%, where:

• Number receiving all doses is the number of surviving infants under one year of age receiving all the required doses during the previous 12 months for the selected vaccine.

• Target population is the total number of eligible infants under one year of age (or total number of surviving infants) at the start of that reporting period [22].

Dropout rate = [(coverage of initial vaccine dose – coverage of ending vaccine dose) ÷ (coverage of initial vaccine dose) × 100], for example (BCG-Measles)/ (BCG) x100.

The dropout rate is the percentage difference in coverage between two different doses in sequence. This therefore, explains why Pentavalent 3 vaccine, which ends the first set of EPI vaccines at the age of 14 weeks, and measles vaccine which ends the EPI vaccines at the age of 9 months were used to calculate the dropout rates. The dropout rate is found by comparing the number of infants who start the immunization schedule with the number who complete it. For example,

The Pentavalent 1 to Pentavalent 3 dropout rate is calculated using the following equation:

Penta 1 to Penta 3 dropout rate = (Penta1 – Penta3) ÷ Penta1 x 100%, where:

• Penta1 is the number (or percentage) receiving the first pentavalent vaccine dose

• Penta3 is the number (or percentage) receiving the third dose.

The Pentavalent 1 to measles vaccine dropout rate is calculated using the following equation:

• Penta1 to measles vaccine dropout rate = (Penta1 – measles) ÷ Penta1 x 100%, where:

• Penta1 is the number (or percentage) of infants receiving the first Pentavalent 1 dose

Measles is the number (or percentage) of infants receiving the measles vaccine [23].

2.9. Sampling Method

A Systematic Random Sampling method was used to select ten from a list of 16 health districts that experienced at least one measles epidemic during the study period according to measles surveillance reports. Firstly, out of the 19 health districts of the North West Region, 16 were selected because they experienced at least a measles epidemic within the study period 2009 to 2015. Secondly, a simple random sampling method was used to select 10 out of the 16 health districts. A health district was include if it had at least 90% completed data for the entire period of study. These health districts were: Bafut, Bali, Bamenda, Benakoma, Fundong, Kumbo West, Mbengwi, Nkambe, Santa, and Tubah Health Districts. Children from aged 0 to 5 years registered in routine immunization activities and all persons reported in measles outbreak listing reports were included. Sampling was consecutive.

2.10. Inclusion Criteria

All cases of persons from age 0 and above, reported in the weekly and monthly reports for routine immunization, routine measles surveillance and line listing reports of measles epidemics were included in the review. A health district must have experienced at least one measles epidemic during the study period, to be included in the study since previous findings from epidemic investigations in the region had pointed to low vaccination coverage, therefore, this would verify the previous findings.

2.11. Exclusion Criteria

This will include cases of measles reported out of routine reporting system and a health district that has not witnessed a measles epidemic during the study period.

2.12. Data Collection Tool

Data was collected using a pre-tested structured form. This form was used to collect data on the number of children vaccinated for BCG, Pentavalent vaccine first, second and third doses, measles vaccine and on measles cases reported following measles epidemics. The Pentavalent vaccine first dose is used to indicate recruitment of children into the EPI programme while the measles vaccine indicates completion of routine EPI vaccines.

2.13. Data Collection Procedure

Data extraction was carried out manually in the office of the data manager for the EPI Programme where data archives for routine immunization and disease surveillance are kept. These data were mainly in hard copy.

2.14. Data Collection Procedure

This involved the number of children recorded (recruited) for vaccination (Pentavalent vaccine 1 coverage); number of children that completed their vaccination calendar (received measles vaccine); and target population per year. The vaccine discrepancies and trends in vaccination coverage per year for the North-West Region were established for BCG; Pentavalent first, second and third doses and the measles vaccine. This was to demonstrate vaccine discrepancies (dropout rates) between these vaccines and then presented alongside the following:

i. The vaccination coverage for the different vaccines BCG, Pentavalent vaccine 1, 2 and 3 and measles vaccine over the years, and

ii. The different years in which measles epidemics were reported in the North West Region alongside the measles vaccination coverage for the concerned year, the age groups affected and period of the year.

2.15. Ethical Consideration

Ethical clearance was obtained prior to administrative authorization, from the University Ethical Committee (The Institutional Review Board of the Faculty of Health Sciences of the University of Buea). This Ethical clearance from the University was validated by the Regional Ethical Committee for the North-West Region and an authorization issued before data collection started. This was to ensure that the protocol was validated and the rights over and security of the data was ensured.

2.16. Data Management

Data collected on daily basis were filed according to districts and date of collection and kept in a designated cupboard at the EPI data manager’s office till extraction was completed. During weekends, the data was entered into an excel spread sheet and stored with a password in the researcher’s laptop.

2.17. Data Analysis

The numerical variables were expressed by their means (± standard deviations). Categorical variables were presented as proportions and percentages.

3. Results

Overall, 1200 monthly District synthesis reports were reviewed for the study period. Out of this number, 1040 reports met the selection criteria and were retained, while 160 reports did not meet the selection criteria and were rejected for the review. The results are presented in Table 1.

Table 1. Annual Vaccination coverage in percentage for BCG; Pentavalent vaccine first, second and third doses; and Measles vaccine in the North West Region

From Table 1 above, the vaccination coverage for BCG vaccine was 56.6% in 2009, 74.5% in 2012 and then dropped to 66.1% in 2014 and rising to 67.4% in 2015. That for Pentavalent vaccine was 60.2% in 2009, 76.8% in 2012, dropped to 67.6% in 2014 before rising to 69.1% by 2015. This same trend was noticed for Pentavalent vaccines second doses rising from 59.3% in 2009 to 74.3% in 2011, dropped to 65.7% in 2014 and then rising to 68.2% in 2015. The vaccination coverage for Pentavalent vaccine third dose was 64.3% in 2009, 75.3% in 2012, dropped to 66.6% in 2014 and increased to 68.5% in 2015. Measles vaccination coverage was 56.2% in 2009, 67.3% in 2012 then dropped to 62.3% in 2014 and then rising to 65.8% in 2015. For all the vaccines, there was a rise in vaccination coverage from 2009 till 2012, then a drop till 2014 and again rising from 2015. Also, the vaccination coverage for all the vaccines were generally low, ranging from about 54.9% to about 76.8%.

It can be seen from Table 1 above that measles vaccination coverage is clearly the lowest among the vaccines considered, and ranged from 54.9% to about 67.9%. It is equally one with an irregular vaccination coverage trend, characterized by “rise and falls”. The Pentavalent vaccine coverage for the first dose was the highest ranging from 60.2% to about 76.8%.

The vaccination coverage for the different vaccines were compared in order to show the discrepancies between these vaccines and presented in Table 2 below.

Table 2. Dropout rates in vaccination coverage between the various vaccines over the years

From Table 2, a majority of the dropout rates (proportion of children who failed receiving the next vaccine as per schedule) for the different vaccines from BCG vaccine administered at birth, through to Pentavalent vaccine third dose (Penta 3), administered at age 14 weeks noticed a negative dropout rates across the years 2009 to 2015. There was a remarkable positive dropout rates across the years from Penta 3 vaccine administered at age 14 weeks to measles vaccine administered at age 9 months. This covers a period of about 22 weeks. This dropout adds to the low vaccination coverage registered for the different vaccines and measles vaccine in particular. A negative dropout indicates that children are admitted into the vaccination programme from elsewhere alone the line at different ages whereas, a positive dropout indicates that children are leaving the programme along the line without completing their vaccination schedule.

Available data for measles epidemics at the RDPH were for 4 consecutive years – 2012, 2013, 2014 and 2015 for the North West Region. This results are presented on the frequency table below, distributed according to age group.

From Table 3, measles epidemics were declared in 2012, 2013, 2014 and 2015; with the number of measles cases being 6, 19, 65 and 300 respectively. This presents 2012 with a small scale of epidemic whereas, 2015 saw a larger scale of measles epidemic in the region. The age groups mostly affected during these epidemics were the 5 to 14 years old 29.0% (113 cases out of 390 cases), followed by the 25 to 59 months age group 21.5% (84 cases out of 390 cases) and then 13 to 24 months old age group 19.0% (74 cases out of 390 cases).

Table 3. Number of measles cases reported per age group during measles epidemics that occurred during the period 2009 to 2015

At a glance, Table 3 above clearly indicates that, the age groups 25 – 59 months and 5 – 14 years were the most affected and then followed by 13 – 24 months and 7 – 12 months. This shows that Measles epidemics trends covered a wide range in age group of children, ranging from as young as 7 months to about 14 years old.

The number of measles cases reported were then grouped according to the month January to December in which they occurred, in order to get the trends in occurrence over the year. The results are presented on the bar chart below.

Figure 1. Bar chart showing the Trends of these epidemics during the months, over the years

According to Figure 1 above, the peaks of measles epidemics are noticed from January to March in the North West Region. This period saw the occurrence of 349 out of the total 390 measles cases line listed during the measles epidemics, making a total of 89.5% (January 37.2%; February 42.8% and March 9.5%) of all measles cases. Measles epidemics were again observed in the month of September in 2013 and 2015.

From the Table 3 above for measles line listed cases, it is seen that the trends in measles epidemics in the North West Region covers children from age 7 months to 14 years and measles epidemics had its peaks covering the month of January to March of the concerned years.

The measles cases line listed during these epidemics also had their vaccination status for measles vaccine documented. From these reports, over 79.0% of the cases were not vaccinated against measles especially for the 2015 measles epidemic. This results is presented on the bar chart below.

Figure 2. Vaccination status of measles cases reported during measles epidemics

Figure 2 above indicates that a majority of persons reported for measles during these measles epidemics were not vaccinated against measles. This phenomenon held same for all the years during which measles epidemics were reported in the NWR of Cameroon.

4. Discussion

Reports for routine EPI vaccination activities, conducted for the target population of children 0 to 5 years old and those for measles outbreaks submitted to the RDPH for the North West Region were reviewed from 2009 to 2015. The vaccines considered were BCG, Pentavalent and Measles vaccines. This was done to establish the vaccination coverage, the discrepancies between the 3 vaccines, their trends and the trend of measles epidemics in the North-West Region.

Measles has been described as an ultrasensitive and merciless marker of low vaccination coverage [7] and would tend to occur in epidemics when the vaccination coverage falls below 80% [1,16], a situation our study observed with a 67.9% in the North West Region. Overall, this study showed low vaccination coverage for BCG, Pentavalent and measles vaccine, ranging from 55.5 – 74.5% for BCG; 60.2 – 76.8% for Penta 1; 59.3 to 74.3% for Penta 2; 64.3 – 75.3% for Penta 3 and 54.1 – 67.9% for measles vaccine. A low Penta 3 vaccination coverage indicating a low EPI coverage (not all target children in the community are admitted into the programme) and a low measles vaccination coverage indicating a low EPI completion rate (only a proportion of children admitted end up receiving all vaccines). Measles vaccination coverage was the lowest (67.9%) recorded and there was as well a high dropout rate of children between Penta 3 and measles vaccine. These findings are similar to those of Luquero et al [21], who found that low measles vaccination coverage (71.1%) was responsible for a long lasting measles epidemics in Maroua, Cameroon while Lo Vecchio et al. [24], found this (74.1%) was responsible for measles being endemic in Southern Italy. The high dropout rates from 2009 to 2015, ranging from 9 to 15.4% implied that not all the children who started with the earlier vaccines completed their vaccination calendar or received measles vaccine. Lo Vecchio et al. reported false contraindications as the reason behind children not completing their routine vaccination. This dropout therefore, increases the proportion of unprotected children in the community as they add to those left out due to the low vaccination coverage. The unprotected children would in turn, favour the occurrence of a measles epidemic when the proportion reaches a critical level of 40% [1]. This is line with findings by Nujum and Varghese who reported that a high dropout rate (15.8%) was responsible for an outbreak in Kerala, India, which would have been averted with an increased measles vaccination coverage [25]. Measles incidence is inversely proportional to routine vaccination coverage, with high incidence associated with low vaccination coverage (71.1%) as reported by Luquerro et al. Therefore, the low measles vaccination coverage of less than 68% could have been responsible for the measles epidemics in the North-West Region from 2012 to 2015. Low measles vaccination coverage in a single dose measles vaccination schedule (as was the case in Cameroon) presents with even a higher level of vulnerability to measles epidemics as evidence shows that populations with high vaccination coverage with a single dose of measles vaccine still experience measles epidemics [26]. According to the WHO one dose of measles vaccine cannot adequately protect a child from contracting measles and so, since 2001, prescribed the administration of 2 measles vaccine doses to each target child [18]. Until April 2020, the EPI programme in Cameroon was issuing one dose of routine measles vaccination to targeted children than the recommended 2 doses by the WHO. Children in Cameroon before 2020 had an opportunity for a second dose of measles vaccine only during supplementary activity (SIA). This finding supports our hypothesis that low measles vaccination coverage favoured the occurrence of measles epidemics in the North-West Region of Cameroon. This finding with low vaccinated coverage is equally in line with that reported by the WHO in Central African Republic (60%) as responsible for a prolong measles epidemic from January 2019 to February 2020 [27].

4.1. Trends in Terms of Age Groups

This study revealed that the age group mostly affected during the measles epidemics was the age group of 5 – 14 years, with 113 (29%) measles cases of the 390 cases for the study period. This results are similar to those of Kouadio et al. that reported a 51.0% of cases being older than 5 years of age [28]. This findings contradicted those of Majawla et al. 2018 in eastern Eastern Uganda which reported children less than 5 years old as the most affected age group during a measles epidemic [29]. This age group was followed by the 25 to 59 months age group, with a total of 84 (22%) of the 390 measles cases. The third hit age group was the 13 to 24 months old with 74 (19%) of the 390 measles cases. Following the analysis, measles epidemics covered a wide range of age groups from as low as 7 months to about 14 years. This findings are similar to those of Umeh and Ahaneke - 2013 in Abba state Nigeria, Thar et al. 2020 in Myanmar [30] and Nimpa et al. 2020 in Madagascar [31].

4.2. Trends in Terms of Period

Epidemics mostly occurred during the months of January, February and March. This three months’ period registered 349 measles cases (89.5%) of the 390 measles cases studied. These findings are in line with that of Fouda et al. 2012 [32], following an epidemic in Nylon Health District, Douala (January to April), but contradicts that of Njim et al. 2016 [17], which reported June to September in the Benakuma Health District of the North West Region. It was also noticed that the peak of measles epidemics occurred in February, which alone registered 167 measles cases (47.9%) of the 349 cases registered from January to March. These findings conforms with that of Delaporte et al in Geneva, Switzerland [33].

A majority of the cases during measles epidemics (79.0%) were unvaccinated and therefore, supported our hypothesis that measles epidemics in the North West Region occurred as a result of low measles vaccination coverage. This result is consistent with that of Jean Baptiste et al. in Nigeria which found 70.8% of unvaccinated cases [34] and that of Girmay and Dadi, who reported even higher rates (83.0%) of unvaccinated measles cases during an epidemic in Ethiopia [35]. Bullo et al. during and outbreak investigation found similar results but with a lower percentage of 64.0% following an outbreak investigation in Parkistan [36].

5. Conclusion

There was a low measles vaccination coverage (67.9%) with an oscillating trend all along the years, and a record of high dropout rates of about15.4 % between Pentavalent third dose vaccine and measles vaccine. Measles epidemics in the North West Region occur due to a low measles vaccination coverage, with a characteristic high dropout rate of children between the Pentavalent vaccine third dose and measles vaccine administered at 9 months of age. These epidemics following reviewed data, would likely occur in the months of January to March, with peaks in February. Measles epidemics would mostly affect children from 5 to 14 years old but at the same time, covers a wide range of children’s age group from as young as 7 months of age. This is characteristic of a population with low measles vaccination coverage, which is supported by the fact that most of the affected children during these epidemics were not vaccinated against measles.

Acknowledgements

I heartily acknowledge the work of this research team comprised of Professor Njamnshi Alfred K., Professor Same Ekobo Albert, Professor Assob Jules Clement and Dr Kum Cletus, who have worked tirelessly for the realization of this study. I also highly appreciate the work of the staff and administrations of the Department of Public Health and Hygiene in particular and the Faculty of Health Sciences at large. Special gratitude goes to Professor Nsagha Dickson Shey for being besides us all the time. I equally thank the administration and staff of the Regional Delegation of Public Health for the North West Region for their collaboration during this study. Gratitude to all my class mates of the Department of Public Health, Faculty of Health Sciences of the University of Buea, for the spirit of unity that continued to reign amongst us even up to this moment in time.

I thank God Almighty for guidance towards a successful realization of this project.

Competing Interest

The authors have no competing interest.

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