Vaccine allocation in a declining epidemic

Article (PDF Available)inJournal of The Royal Society Interface 9(76):2798-803 · July 2012with10 Reads
DOI: 10.1098/rsif.2012.0404 · Source: PubMed
Sizeable quantities of 2009 pandemic influenza A/H1N1 (H1N1pdm) vaccine in the USA became available at the end of 2009 when the autumn wave of the epidemic was declining. At that point, risk factors for H1N1-related mortality for some of the high-risk groups, particularly adults with underlying health conditions, could be estimated. Although those high-risk groups are natural candidates for being in the top priority tier for vaccine allocation, another candidate group is school-aged children through their role as vectors for transmission affecting the whole community. In this paper, we investigate the question of prioritization for vaccine allocation in a declining epidemic between two groups-a group with a high risk of mortality versus a 'core' group with a relatively low risk of mortality but fuelling transmission in the community. We show that epidemic data can be used, under certain assumptions on future decline, seasonality and vaccine efficacy in different population groups, to give a criterion when initial prioritization of a population group with a sufficiently high risk of epidemic-associated mortality is advisable over the policy of prioritizing the core group.

Full-text (PDF)

Available from: · License: CC BY
    • "The same type of pattern transitions is found in many epidemiological systems including those that account for evolutionary dynamics [106, 107], cross immunity [108], demographic factors [47], and adaptive behavior [109, 110, 111]. In an epidemic, the initial state of the infected population may play an important role in the dynamics of the disease [112, 113]. Based on epidemiological models formulated in terms of reaction-diffusion equations, it is shown that changing the initial conditions induces the transition from a spiral wave to a target wave (Fig. 9). "
    [Show abstract] [Hide abstract] ABSTRACT: Infectious diseases are a threat to human health and a hindrance to societal development. Consequently, the spread of diseases in both time and space has been widely studied, revealing the different types of spatial patterns. Transitions between patterns are an emergent property in spatial epidemics that can serve as a potential trend indicator of disease spread. Despite the usefulness of such an indicator, attempts to systematize the topic of pattern transitions have been few and far between. We present a mini-review on pattern transitions in spatial epidemics, describing the types of transitions and their underlying mechanisms. We show that pattern transitions relate to the complexity of spatial epidemics by, for example, being accompanied with phenomena such as coherence resonance and cyclic evolution. The results presented herein provide valuable insights into disease prevention and control, and may even be applicable outside epidemiology, including other branches of medical science, ecology, quantitative finance, and elsewhere.
    Full-text · Article · Aug 2016
    • "A c c e p t e d M a n u s c r i p t 15 targeting mitigation efforts to the older adults increases during an epidemic's decline stage compared to the ascent stage [20]. For epidemics associated with influenza A/H1N1, the role of school-age children decreased significantly in the post-pandemic period compared to the pandemic itself, presumably due to the immunity acquired during the pandemic when attack rates among 5-17 year-olds were very high [1] . "
    [Show abstract] [Hide abstract] ABSTRACT: The identification of key “driver” groups in influenza epidemics is of much interest for the implementation of effective public health response strategies, including vaccination programs. However, the relative importance of different age groups in propagating epidemics is uncertain. During a communicable disease outbreak, some groups may be disproportionately represented during the outbreak's ascent due to increased susceptibility and/or contact rates. Such groups or subpopulations can be identified by considering the proportion of cases within the subpopulation occurring before (Bp) and after the epidemic peak (Ap) to calculate the subpopulation's relative risk, RR =Bp/Ap. We estimated RR for several subpopulations (age groups) using data on laboratory-confirmed US influenza hospitalizations during epidemics between 2009 and 2014. Additionally, we simulated various influenza outbreaks in an age-stratified population, relating the RR to the impact of vaccination in each subpopulation on the epidemic's initial effective reproductive number Re(0). We found that children aged 5–17 had the highest estimates of RR during the five largest influenza A outbreaks, though the relative magnitude of RR in this age group compared to other age groups varied, being highest for the 2009 A/H1N1 pandemic. For the 2010–2011 and 2012–2013 influenza B epidemics, adults aged 18–49, and 0–4 year-olds had the highest estimates of RR, respectively. For 83% of simulated epidemics, the group with the highest RR was also the group for which initial distribution of a given quantity of vaccine would result in the largest reduction of Re(0). In the largest 40% of simulated outbreaks, the group with the highest RR and the largest vaccination impact was children 5–17. While the relative importance of different age groups in propagating influenza outbreaks varies, children aged 5–17 play the leading role during the largest influenza A epidemics. Extra vaccination efforts for this group may contribute to reducing the epidemic's impact in the whole community.
    Full-text · Article · May 2015
  • [Show abstract] [Hide abstract] ABSTRACT: During public health emergencies, the Military Health System experiences challenges similar to those across the U.S. public and private health systems. This study explored how 1 such event, the 2009/2010 influenza (H1N1) pandemic, impacted health care utilization and associated costs in the Military Health System. Data from the Military Data Repository were used to examine diagnoses, claims data, and dates of services with respect to military or civilian care during 2004-2009/2010 influenza seasons. Comparison analysis was conducted through two-tailed t-tests and regression models. There was a significant increase in inpatient and outpatient health care utilization during the 2009/2010 H1N1 pandemic year, most markedly for emergency department visits. The 2009/2010 H1N1 pandemic cost the Department of Defense $100 million compared to influenza-related health care costs incurred in previous influenza seasons. Highest health care utilization costs were found in children less than age 5. The greatest cost burden was attributed to immunizations for active duty personnel delivered at military facilities. Annual trend analysis of costs and health care utilization would be helpful to plan and resource emerging influenza pandemics and to identify subgroups at greatest risk for contracting influenza.
    Article · Jun 2013
Show more