Vaccines | Free Full-Text | Strategic Planning of a Joint SARS-CoV-2 and Influenza Vaccination Campaign in the UK

The World Health Organization (WHO) declared Severe Acute Respiratory Syndrome Corona Virus 2 (aka corona virus disease 2019 or COVID-19) a pandemic on 11 March 2020 [1,2,3,4] after the emergence of the virus in Wuhan, China. COVID-19 has claimed the lives of around 6.2 million individuals globally, and around 58.1 million individuals are still infected with the highly contagious virus [5,6,7]. Even though governments and non-governmental organisations have made funds available to fight COVID-19 [8,9,10,11,12], and the global vaccination programmes against COVID-19 have been largely successful, especially in high-income countries [13,14,15,16,17,18], the disease is still prevalent around the globe [19,20,21]. This is partly due to the emergence of new variants (e.g., Alpha (B.1.1.7), Beta (B.1.351), Delta (B.1.617.2), and Omicron (B.1.1.529)) [22,23,24,25] that render the current vaccines less effective. Booster jabs (e.g., BNT162b2 developed by Pfizer and BioNTech [26,27,28] and mRNA-1273 developed by Moderna [29,30,31]) have been developed and administered to high-risk and vulnerable individuals to avoid developing complications that could lead to hospitalisation or even death. Similarly, the influenza virus (e.g., A(H1N1), A(H3N2), and B/Victoria lineage) [32,33,34,35] has been around for some time, and high-risk and vulnerable individuals are required to take an annual flu jab to boost immunity and to reduce the impact of the disease within society. For the first time, SARS-CoV-2 and influenza vaccines are distributed and administered simultaneously, posing significant logistical and distribution challenges. For example, SARS-CoV-2 and influenza vaccines require different types of storage technologies, especially RNA-based SARS-CoV-2 vaccines that need to be stored and transported at ultra-low temperature (ULT) conditions. Consequently, an effective and efficient planning method would be required for the vaccination campaigns to be successful.

During a vaccination campaign, vaccines are delivered through complex supply chains, which typically comprise manufacturing facilities, intermediate storage locations such as warehouses and vaccine stores, and administration points (GP surgeries, hospitals, pharmacies, clinics, and mass vaccination centres). The design and planning of vaccine supply chains require optimal selection of storage locations, production planning at manufacturing plants, inventory management, distribution planning, storage capacity planning, selection of routes and transport types, etc. In previous work, a general purpose simulation-based analytical tool known as HERMES—Highly Extensible Resource for Modeling Supply Chains was used to (i) assess the performance of a vaccine supply chain [36,37,38,39], (ii) plan the introduction of new vaccines against rotavirus and pneumococcus [40], and (iii) redesign a vaccine supply chain to allow access of vaccines during routine and supplementary vaccination campaigns in low- and middle-income countries [41,42,43]. However, HERMES does not support the optimisation of supply chains, leading to solutions that could be suboptimal. Cavalho et al. [44] considered three performance indicators (economic, environmental, and social performance) to develop a multi-objective mixed-integer linear programming (MO-MILP) model for the optimal design and planning of a sustainable vaccine supply chain. A case study on the distribution of vaccines against poliomyelitis and MMR (measles, mumps, and rubella) within Europe indicated that the proposed model is capable of obtaining solutions that are economically relevant and would also lead to a low global warming potential. Kis et al. [45] proposed a steady-state MILP model for the distribution of vaccine candidates developed using various platform technologies such as RNA vaccines, outer membrane vesicle vaccines with genetically customisable membrane antigens, virus-like particle vaccines with genetically configurable epitopes, and humanised yeast-produced vaccines. The model indicated both the supply chain configuration and delivery type that would lead to a maximum net present value.

More recently, Georgiadis and Georgiadis [46] addressed the distribution of SARS-CoV-2 vaccines in Greece. The MILP model proposed by the authors takes into account the storage, distribution, and administration aspect of the vaccine supply chain. However, their model does not account for quality control (QC) checks; fill-finish plants; production planning; selection of transport mode; and, most importantly, management of vaccine thermal shippers. Ibrahim et al. [47] proposed a novel supply chain model that addresses the complexities related to the supply and distribution of vaccine candidates developed using the most advance platform technologies. By considering the essential components of the supply chain (such as manufacturing and fill-finish plants, storage locations, administration points, transport modes, quality control checks, and management of thermal shippers), the authors developed an MILP supply chain model for the distribution and administration of RNA SARS-CoV-2 vaccines (BNT162b2—Comirnaty^®) in the UK. The outcomes from this work indicated that the proposed model can identify economically optimal supply chains in addition to revealing locations where stockouts could occur should there be a shortage in vaccine supply. The authors extended the model to incorporate SARS-CoV-2 vaccines developed using other platform technologies, such as viral vectors (AZD1222—Vaxzevria^®), in addition to RNA vaccines (BNT162b2—Comirnaty^®) [48]. None of the aforementioned works have addressed the challenges involved in planning of simultaneous SARS-CoV-2 and influenza vaccination campaigns.

The remainder of this article is organised as follows. Section 2 presents the proposed vaccine supply chain model. Section 3 presents the case study information, while Section 4 presents and discusses the outcomes from this work. Lastly, Section 5 concludes the paper and presents future work.

To successfully accomplish the SARS-CoV-2 and influenza vaccination campaigns, sufficient doses of the recommended vaccines must be made available in order to satisfy demand, i.e., the number of patients arriving at vaccination centres to be inoculated with the vaccines. The vaccine demand profile shown in Figure 2 is an important tool that can be utilised by the government and policy makers to set out vaccine procurement strategies ahead of the simultaneous SARS-CoV-2 and influenza vaccination campaigns. By December 2021, the UK government secured the supply of 114 million doses of SARS-CoV-2 vaccines to cover SARS-CoV-2 vaccination campaigns in Years 2022 and 2023 [57,58,59]. The procured vaccine doses consist of 54 million BNT162b2 and 60 million mRNA-1273. As can be deduced from Figure 2, the total doses required for the SARS-CoV-2 vaccination campaign is ≈55 million doses, which is 52% lower than the total doses procured. Hence, the total doses procured by the UK government are sufficient to cover two SARS-CoV-2 vaccination campaigns as expected. Looking forward, the analysis presented here can be used to update the current SARS-CoV-2 vaccine demand, especially when the UK government and policy makers decide to add more cohorts to the existing ones.

From the economic analysis in Section 4.2, the overall cost of vaccinating target individuals against SARS-CoV-2 and the influenza virus is approximately 7.2 billion USD, of which the logistics cost constitutes the largest percent (47%), followed by the vaccine procurement cost (29%). The logistics cost is the sum of the total capital cost, total operating cost, and total transportation cost. As can be seen in Figure 4a,b, the cost to be invested in cold chain infrastructure dominates the logistics cost of the combined SARS-CoV-2 and influenza vaccines supply chain, while the transportation investment is the smallest component. Furthermore, Figure 4b indicates that the cost of transporting SARS-CoV-2 vaccines contributes around 77.1% of the total transportation cost. The SARS-CoV-2 vaccines BNT162b2 and mRNA-1273 are manufactured by Pfizer-BioNTech and Lonza, with the manufacturing plants located in Puur, Belgium, and Basel, Switzerland, respectively. These vaccine candidates are airlifted to central warehouses in the UK (London, Edinburg, Cardiff, and Belfast) before distribution to regional stores and later to administration points, consequently leading to the high cost of transportation compared with influenza vaccine candidates manufactured in the UK, which do not need air transport.

Investigation of the impact of SARS-CoV-2 vaccine type on total vaccination cost indicates that the vaccination cost of BNT162b2 is 14% lower than mRNA-1273, even though BNT162b2 requires a more expensive cooling technology (ULT freezer operating at −80 °C) as well as thermal shippers and dry ice. This analysis shows that the procurement cost of a more thermostable RNA SARS-CoV-2 vaccine outweighs the cost savings resulting from the use of moderate cooling technology (conventional freezer operating at −24 °C) during the storage and transport of SARS-CoV-2 vaccines. Although BNT162b2 has the lowest total cost, its supply chain is more complex and difficult to operate, requiring a system for the effective management of thermal shippers and dry ice as well as temperature monitoring during storage and transportation in order to control temperature excursions that could compromise the potency of the vaccines. Owing to the challenges in handling BNT162b2, this vaccine type is likely to lead to more vaccine wastage compared to mRNA-1273, as reports have indicated several million doses of SARS-CoV-2 vaccines have already been wasted [60,61,62,63]. Once the vial of BNT162b2 is thawed at room temperature, it is expected to be used within two hours; afterwards, any unused doses must be discarded as waste. mRNA-1273 can last for up to twelve hours at room temperature. Also, vials of BNT162b2 can be stored for only five days at 2–8 °C compared to 30 days for mRNA-1273. From the logistics viewpoint, the longer shelf life at 2–8 °C means large quantities of vaccines can be stored at vaccine administration points, thereby decreasing delivery frequency and consequently the logistics cost. This point is reflected in Figure 7, which shows that the logistics cost of BNT162b2 and mRNA-1273 constitute 29.7% and 25.7% of the total cost, respectively.

Ahead of the simultaneous SARS-CoV-2 and influenza vaccination campaign, the curve shown in Figure 6 can be used to estimate the total vaccination cost depending on the type of SARS-CoV-2 vaccine the UK government intends to roll out. This information is vital and can facilitate efficient and effective logistical and financial planning, ensuring that the contract for the supply of vaccines is within the overall budget.

There is no vaccination administration in Weeks 1 and 2, as the initial batches of the vaccines undergo quality control checks at central warehouses. Recall that it was assumed that SARS-CoV-2 vaccination commences two weeks after influenza, meaning individuals inoculated with flu jabs in Week 3 will return to the administration point for their SARS-CoV-2 vaccine in Week 5. Thus, in Figure 8, both SARS-CoV-2 and influenza vaccines are administered between Weeks 5 to 27. Apart from showing the progress of the vaccination campaign, Figure 8 can be used to estimate the approximate capacity of vaccine administration points in the twelve regions of the UK. The capacity required to ensure a successful vaccination campaign in Cardiff, Edinburgh, Belfast, North East, North West, Yorkshire and the Humber, East Midlands, West Midlands, East of England, London, South East, and South West correspond to 0.212, 0.573, 0.418, 0.376, 0.447, 0.479, 0.698, 0.714, 0.475, 0.315, 0.673, and 0.256 million doses per week, respectively. Prior to the joint SARS-CoV-2 and influenza vaccination campaigns, this information can be used to plan the capacities of administration points in order to accommodate the number of individuals arriving per week. Failure to provide enough capacity could lead to a drop in the vaccination rate and immunisation coverage, which could lead to a surge in infection rates, hospitalisations, and deaths.