Although little is known about vaccination in West Africa before the colonial era, research showed the involvement of colonial doctors in introducing vaccines to Africa. With the help of their European counterparts, they built laboratories called Pasteur Institutes for vaccine production.1

Inasmuch as vaccination began in Nigeria during the colonial era, the World Health Organization (WHO) formally created the Expanded Program on Immunization (EPI) in Africa in 1974 with the aim of eradicating six diseases: polio, measles, diphtheria, pertussis, tuberculosis, and tetanus. In 1978, Nigeria’s EPI was created by the World Health Organization (WHO) with the aim of providing vaccines against the six aforementioned diseases for children aged 0-2 years. This intervention’s coverage peaked in the early 1990s reaching 81.5% of Nigeria’s children population.2

The Nigerian government changed the EPI to the National Programme on Immunization (NPI) in 1996 to show its dedication to the programme. Eventually, the NPI was merged with the National Primary Health Care Development Agency (NPHCDA) in 2007, the agency in charge of primary health care (PHC). Nigerians are vaccinated according to the NPI schedule and are expected to have completed the schedule by the age of one. Additionally, house-house polio campaigns are held in order to maintain a polio-free status.

# COLD-CHAIN SYSTEM IN NIGERIA

Vaccine cold-chain management is essential for vaccine transportation and storage in a potent state from the manufacturer to the point of use. This requires suitable cold chain infrastructure, compliance with standards, and effective management. In most countries, the vaccine cold-chain system consists of cold rooms, freezers and ice-lined refrigerators, cold boxes, vaccine carriers, ice packs and personnel. Distribution of vaccines in Nigeria would follow the political divisions of the country. Nigeria consists of six geopolitical zones further divided into a Federal Capital Territory and thirty-six states which are further divided into 774 local government areas (LGA). The cold-chain system of the country is made up of five strata; the National Strategic Cold Store (NSCS) which is the primary storage site for all vaccines in the country, six zonal stores located in each geopolitical zone in the country receive supplies from the NSCS, state stores receive supplies from zonal stores, LGA stores receive vaccines from their state store and the PHC centers get supplies from LGA store.3

## Challenges of the cold-chain system

### Poor infrastructure

With the persistent increase in population, onset of new diseases, advent of novel vaccines and breakdown of cold chain equipment (CCE), the current cold chain capacity is bound to be insufficient. Findings suggest that Nigeria currently has a cold chain capacity of 201m2 and needs a total capacity of 672m2 to meet up with demands. Hence, there is a 70% deficit of the routine maximum demand.3 With reference to the ultra cold chain capacity of Nigeria, Dr Faisal Shuaib, the Executive Director of the National Primary Healthcare Development Agency, disclosed during a tour of the National Strategic Cold Store (NSCS) in Abuja that the NSCS has three ultra-cold chain equipment which have a combined capacity of 2100 litres; operate at a temperature of -85°C and can store up to 400,000 doses of the Pfizer vaccine.4

Additionally, with the current design of the Nigerian cold chain system and possession of 6340 CCE as against the 9565 CCE needed to achieve coverage in every ward in the country, there is a CCE gap of 3225; an overt deficit that negatively impacts vaccination coverage.3 Also, it was reported that in some facilities in Ile-Ife, equipment needed to maintain the cold chain were lacking as only 37.1% had thermometers, 31.4% had refrigerators for storing vaccines, 45.7% had cold boxes and only 20% had emergency trays. Furthermore, electricity and water supply were available in only 31.4% and 45.7% of the facilities respectively.5 Findings from a study done in Oyo revealed that epileptic power supply and absence of generator fuel were the major challenges faced in storage facilities while others were insufficient backup refrigerators and cold boxes, poor temperature monitoring tools among others.6

The efficiency of the cold chain system has also been deterred by the use of dated equipment, limited integration of technology as many facilities still make use of stem thermometers while continuous temperature trackers and loggers as well as temperature-sensitive alarms are generally lacking at storage sites. Hence, out-of-range temperature may often go undetected when the monitors are not on site and this culminates in poor temperature monitoring and control and reduced potency of vaccines.6

### Subpar training of cold chain workers

Another study conducted in 35 immunization clinics in Ile-Ife, Southwest Nigeria, showed that only 54% of vaccinators were aware of the shake test, only 19% could interpret colour changes on a vaccine vial monitor and just 29% of respondents kept record of vaccine stock-on-hand.5

### Difficulty transporting vaccines to endpoints

Availability of potent vaccines in sufficient quantity to the end users is crucial to the success of the cold chain. However, there are areas that are difficult to reach due to unnavigable terrain, poor access roads and distance to storage sites.10 Individuals in hard-to-reach areas consequently have low vaccination coverage. A study revealed that over one-third of polio in 2013 were from under-immunized and hard-to-reach areas and vaccine coverage in some of these areas was as low as 23% for Oral Polio Vaccine 3 and 22% for Pentavalent vaccine 3.11 Although transportation from national to state stores is quite reliable, there are numerous breakdowns in the supply chain from local cold stores to endpoints.

These unacceptable indices aren’t peculiar to Nigeria. Drawing comparisons with Ghana, a study carried out in a rural district in Ghana revealed an average score of 60%, 32%, 27%, 53% and 16% in the areas of temperature control, stock management, distribution, vaccine management and information system respectively.12 Similarly, exposure of vaccines to out-of-range temperature is a widespread problem in Cameroon as studies conducted in forty health facilities located in 8 districts in Cameroon revealed that only 52.5% (21 of 40 facilities), 20.6% (7 of 34 facilities) had at least one freezer and constant power supply respectively while almost 27.5% of the health facilities were conducting EPI activities without any cold chain equipment.13 Similarly, a study conducted in 94 health centres in the Central Region in Togo revealed that approximately 30% of these facilities lacked refrigerators for storing vaccines while 19% had refrigerators were out damaged or out of commission.14 Overall, there is limited progress in achieving universal access to immunization in sub-Saharan Africa as only 13% of countries in the region achieved 80% coverage in each district in 2015 and in 2016, only 19% of the countries supported by the Global Alliance for Vaccines and Immunization met the WHO’s 80% benchmark for effective vaccine management.15

# STORAGE PECULIARITIES OF COVID-19 VACCINES

The advent of the COVID-19 vaccines have ushered in a ray of hope in dealing with this deadly pandemic. However, low- and middle-income countries (LMIC) such as Nigeria need to figure out how to protect its teeming population and meet up with the storage requirements of the vaccines.

The Pfizer and Moderna vaccines were designed with mRNA technology that requires intensely cold storage to elongate shelf-life. The Pfizer variant requires storage at -70°C ± 10°C for up to ten days unopened and on getting to its point of use, it can either be stored in ultra-low temperature freezers for up to six months, in thermal shippers for up to 30 days whilst refilling with dry ice every five days and regular hospital refrigeration units at 2-8°C for up to five days. Once thawed or refrigerated under 2-8°C, the vaccine cannot be refrozen.16 On the other hand, the Moderna variant can be stored at -20°C for up to six months, 2-8°c for up to 30days within the six-month shelf life after thawing and at room temperature for up to 12hours.17

The Oxford-AstraZeneca vaccine uses double-stranded DNA technology unlike the single-stranded mRNA technology employed by Pfizer and Moderna. Hence, it has lower chances of degrading at lower temperatures and can therefore be stored at regular refrigerator temperature. Consequently, it has a shelf-life of 6months when refrigerated at 2-8°C. Furthermore, the Oxford-AstraZeneca vaccine costs US$3-4 (N1,143-1,524) as opposed to US$37 (N14,098) for Moderna and US\$20 (N7621) for Pfizer.18

# SOLUTIONS ON STORAGE AND DISTRIBUTION

History has demonstrated that a vaccine in itself is not a panacea; it is pertinent that logistical and cold-chain systems are efficient in the storage and distribution of vaccines to ensure potency upon administration. Owing to the high cost and storage requirements of the Moderna and Pfizer vaccines respectively, the Oxford-Astrazeneca vaccine appears a feasible alternative for LMICs like Nigeria. While challenges with the Nigerian cold chain system abound, the following can be employed to ensure success in vaccinating majority of Nigerians against the novel coronavirus:

Reorganize supply chain. The Federal Government of Nigeria is in control of two levels of the chain including the NSCS. A 3-hub system was designed to reduce the burden on the NSCS after an analysis of the NPHCDA storage challenges. The 3-hub system involves Kano, Abuja (NSCS) and Lagos zonal storage sites receiving vaccines directly from suppliers and delivering them directly to States Studies show that moving from the two tier federal system to a single 3-hub federal system would reduce storage needs by 30%3 lower cost of operations leaving zonal stores available for a sudden increase in capacity requirement. Additionally, the implementation of the 3-hub federal system will foster prompt availability of vaccines to states by eliminating the zonal level.

Increase storage capacity and integration of recent technology. Effective storage of vaccines is an integral component of the supply chain management as it ensures that vaccines do not lose their potency. Recent study showed that for current vaccine programs e.g. Polio, Bacillus Calmette-Guerin, Tetanus etc., there is a need for increase in storage capacity at all zonal levels within the federation to reach 100% reliability. Therefore, an expansion of the current storage facilities is a prerequisite prior to acquiring the coronavirus vaccines. Due to the unreliability of Nigeria’s power sector, funding should be channeled towards procuring clean and efficient cooling technologies such as solar-powered refrigerators. Additionally temperature monitoring and control devices should be introduced into the cold chain system. These devices give real-time temperature, alert workers when out-of-range temperatures are detected causing them to intervene and ultimately preserve the potency of vaccines and prevent wastage.

Train vaccinators and technicians. In other to meet up with the need to rapidly vaccinate as many Nigerians as possible, vaccinators who can be mobilized swiftly will be required. As such, the number of vaccinators required may exceed the number of currently trained and experienced vaccinators, particularly because the existent immunization workforce will be required to maintain the NPI. It is unarguably a necessity that the vaccinators for COVID-19 receive comprehensive training and competency assessment to ensure that those who receive the vaccine are safe and more so, public confidence in the process is established. A complete online course on COVID-19 vaccination training has been drafted by the WHO in conjunction with the United Nations Children’s Fund (UNICEF) for use by countries in the training of frontline health workers. This resource can be adapted by Nigeria’s Ministry of Health, translated to major ethnic dialects, and used in the training of the nation’s COVID-19 vaccination workforce.

Additionally, maintenance and repair of CCE requires extensive technical know-how. The average time taken to repair a fridge at the LGA level of the cold chain in Nigeria is two months to two years. Hence, it is important for Nigeria to adopt hands-on training approach of technicians at local technical colleges and tertiary institutions and spare parts for CCEs should also be made readily available. This will create an extensive workforce that can promptly detect and tackle problem with CCEs and this will ultimately strengthen storage and distribution capacity. This method which was adopted in Ethiopia led to the training of 516 technicians and restoration of 100m2 CCE capacity. CCE maintenance and repair is currently in the module of some technical colleges in Ethiopia and Tanzania.19

Estimation of capacity and vaccine needs is pivotal to the efficiency of the cold chain given that it takes approximately two years to procure and install cold chain equipment.19 Needs estimation can be done using previous consumption (assessed at the national level), target population (assessed at the national level) and size of immunization sessions (assessed at the primary health centres and other facilities where the vaccines are given)20 Veritable data also needs to be taken particularly at the local level where visibility into vaccine inventory levels is generally lower as the accuracy of forecasting and needs estimation depends on the source data used.3 The WHO EPI forecasting tool is very useful for this process as it analyses different scenarios and also provides a multiyear forecast (three to five year period) of vaccines, safe injection supplies, storage capacity and cold chain equipment.20

## Development of mobile sessions for hard-to-reach areas

In order to ensure adequate coverage in hard-to-reach areas, immunization outreaches and adoption of non-generic transportation methods to circumvent transportation barriers should be considered. Mobile teams should be created and equipped with boats for coastland and other vehicles capable of navigating various terrains.

# DISTRIBUTION OF COVID-19 VACCINES

Salient ethical considerations should guide the distribution of the COVID-19 vaccines. In light of the limitation in vaccine supply, the WHO Strategic Advisory Group of Experts on Immunization (SAGE) proposed a 3-stage prioritization roadmap for vaccine administration where (1-10 % of a country’s total population is vaccinated in Stage 1, (11-20)% in Stage 2, and (21-50)% in Stage 3.21 The public health strategy employed in the administration of vaccines should depend on the burden of disease and the local epidemiology. The current epidemiological setting in Nigeria is that of community transmission.22 Hence, health workers and older adults within the country-defined specific age cut-off should be prioritized for vaccination in Stage 1. In stage 2, older adults not covered in stage 1 including persons with comorbidities, disadvantaged or persecuted groups, sexual minorities, people living with disabilities, refugees, internally displaced persons, health workers involved in immunization delivery, high priority teachers and school staff should be vaccinated. In stage 3, other teachers and school staff, other essential workers outside health and education sectors, pregnant women etc. should receive the vaccine.21

# CONCLUSIONS

Despite the numerous challenges plaguing the system, opportunities are equally numerous. A sturdy roadmap, strong political will and intense collaborations will increase the feasibility of the proposed solutions. Accurate data collection and appropriation of funds should also be prioritized in order to design and implement the aforementioned solutions. With a teeming population of over 200million people, extreme poverty levels, limited primary health centres, cold chain equipment and storage capacity, procurement of the OxfordAstraZeneca variant is more in consistence with our realities if we are going to achieve a nationwide coverage. Finally, outsourcing a carefully calculated percentage of storage and distribution to accredited private facilities under the purview of the local government may reduce the burden of vaccine storage on the government and facilitate effective and efficient vaccination against covid-19 in the country culminating in eradication of COVID-19 in Nigeria.

None

## Authorship contributions

All authors contributed equally to the draft and final version of the manuscript

## Competing interests

All authors have completed the Unified Competing Interest form available at http://www.icmje.org/conflicts-of-interest/ in line with the Journal of Global Health editorial policy and declare no conflicts of interest.

## Correspondence to:

Shamsudeen Ayomide Usman

St. Nicholas Hospital, Lagos, Nigeria

[email protected]