The benefits of combining early aspecific vaccination with later specific vaccination

V accination is an effective way to prevent an epidemic. It results in immunity for the vaccinated individuals, but it also reduces the infection pressure for unvaccinated people. Thus people may actually escape infection without being vaccinated: the so-called "herd effect." We analytically study the relation between the herd effect and the vaccination fraction for the seminal SIR compartmental model, which consists of a set of differential equations describing the time course of an epidemic. We prove that the herd effect is in general convex-concave in the vaccination fraction and give precise conditions on the epidemic for the convex part to arise. We derive the significant consequences of these structural insights for allocating a limited vaccine stockpile to multiple non-interacting populations. We identify for each population a unique vaccination fraction that is most efficient per dose of vaccine: our dose-optimal coverage. We characterize the solution of the vaccine allocation problem and we show the crucial importance of the dose-optimal coverage. A single dose of vaccine may be a drop in the ocean, but multiple doses together can save a population. To benefit from this, policy makers should select a subset of populations to which the vaccines are allocated. Focusing on a limited number of populations can make a significant difference, whereas allocating equally to all populations would be substantially less effective.

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“…As the epidemic continues to spread in the meantime, this brings extra complexity to the problem (cf., Duijzer et al. ).…”

Section: Discussion Of Assumptionsmentioning

confidence: 99%

Dose‐Optimal Vaccine Allocation over Multiple Populations

Duijzer

Jaarsveld

Wallinga

et al. 2018

Production and Operations Management

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118

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“…We see these two aspects in some US pandemic response plans, which describe the importance of stockpiling prepandemic vaccines and investing in vaccine manufacturing capacity (U.S. Department of Health and Human Services, 2005;Homeland Security Council, 2006; U.S. Department of Health and Human Services, 2017). However, apart from a recent working paper (Duijzer et al, 2017a) little to no research has been conducted on the budget allocation problem that results from the tradeoff between these two aspects. This problem is typical for sudden outbreaks, because uncertainty regarding the timing of the outbreak and the disease causing it complicate the analysis of the trade-off between stockpiling and reserving production capacity.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Literature review: The vaccine supply chain

Duijzer

Jaarsveld

Dekker

2018

European Journal of Operational Research

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172

146

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Vaccination is one of the most effective ways to prevent and/or control the outbreak of infectious diseases. This medical intervention also brings about many logistical questions. In the past years, the Operations Research/Operations Management community has shown a growing interest in the logistical aspects of vaccination. However, publications on vaccine logistics often focus on one specific logistical aspect. A broader framework is needed so that open research questions can be identified more easily and contributions are not overlooked. In this literature review, we combine the priorities of the World Health Organization for creating a flexible and robust vaccine supply chain with an Operations Research/Operations Management supply chain perspective. We propose a classification for the literature on vaccine logistics to structure this relatively new field, and identify promising research directions. We classify the literature into the following four components: (1) product, (2) production, (3) allocation, and (4) distribution. Within the supply chain classification, we analyze the decision problems for existing outbreaks versus sudden outbreaks and developing countries versus developed countries. We identify unique characteristics of the vaccine supply chain: high uncertainty in both supply and demand; misalignment of objectives and decentralized decision making between supplier, public health organization and end customer; complex political decisions concerning allocation and the crucial importance of deciding and acting in time.

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“…The shorter campaign duration is because there is no initial delay in campaign commencement due to the elimination of the need for ice packs to transport the vaccines in the last mile of the campaign. During measles outbreak response vaccination, a quick response, assuming no loss of vaccination coverage, is always preferable in minimizing outbreak size [24,[27][28][29][30][31].…”

Section: Discussionmentioning

confidence: 99%

Modelling the relative benefits of using the measles vaccine outside cold chain for outbreak response

Azam

Saitta

Bonner

et al. 2021

Preprint

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Introduction Rapid outbreak response vaccination is a strategy for measles control and elimination. Measles vaccines must be stored and transported within a specified temperature range, but this can present significant challenges when targeting remote populations. Measles vaccine licensure for delivery outside cold chain (OCC) could provide more vaccine transport/storage space without ice packs, and a solution to shorten response times. However, due to vaccine safety and wastage considerations, the OCC strategy will require other operational changes, potentially including the use of 1-dose (monodose) instead of 10-dose vials, requiring larger transport/storage equipment currently achieved with 10-dose vials. These trade-offs require quantitative comparisons of vaccine delivery options to evaluate their relative benefits. Methods We developed a modelling framework combining elements of the vaccine supply chain - cold chain, vial, team, and transport equipment types - with a measles transmission dynamics model to compare vaccine delivery options. We compared 10 strategies resulting from combinations of the vaccine supply elements and grouped into three main classes: OCC, partial cold chain (PCC), and full cold chain (FCC). For each strategy, we explored a campaign with 20 teams sequentially targeting 5 locations with 100,000 individuals each. We characterised the time needed to freeze ice packs and complete the campaign (campaign duration), vaccination coverage, and cases averted, assuming a fixed pre-deployment delay before campaign commencement. We performed sensitivity analyses of the pre-deployment delay, population sizes, and two team allocation schemes. Results The OCC, PCC, and FCC strategies achieve campaign durations of 50, 51, and 52 days, respectively. Nine of the ten strategies can achieve a vaccination coverage of 80%, and OCC averts the most cases. Discussion The OCC strategy, therefore, presents improved operational and epidemiological outcomes relative to current practice and the other options considered.

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The benefits of combining early aspecific vaccination with later specific vaccination

Cited by 28 publications

References 58 publications

Dose‐Optimal Vaccine Allocation over Multiple Populations

Dose‐Optimal Vaccine Allocation over Multiple Populations

Literature review: The vaccine supply chain

Modelling the relative benefits of using the measles vaccine outside cold chain for outbreak response

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