Perspectives on the Impact of Varicella Immunization on Herpes Zoster. A Model-Based Evaluation from Three European Countries

Poletti, Piero; Melegaro, Alessia; Ajelli, Marco; Fava, Emanuele Del; Guzzetta, Giorgio; Faustini, Luca; Tomba, Giampaolo Scalia; Lopalco, Pietro Luigi; Rizzo, Caterina; Merler, Stefano; Manfredi, Piero

doi:10.1371/journal.pone.0060732

Cited by 69 publications

(77 citation statements)

References 56 publications

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“…The paper focused on the 'fullboosting' hypothesis considered by recent public health modelling [12,13,15,17], according to which each re-exposure to varicella yields a CMI boosting event. As the exact magnitude of the boosting effect is still unclear [7] this might be debatable.…”

Section: Discussionmentioning

confidence: 99%

Perspectives on optimal control of varicella and herpes zoster by mass routine varicella vaccination

et al. 2016

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Herpes zoster arises from reactivation of the varicella-zoster virus (VZV), causing varicella in children. As reactivation occurs when cell-mediated immunity (CMI) declines, and there is evidence that re-exposure to VZV boosts CMI, mass varicella immunization might increase the zoster burden, at least for some decades. Fear of this natural zoster boom is the main reason for the paralysis of varicella immunization in Europe. We apply optimal control to a realistically parametrized age-structured model for VZV transmission and reactivation to investigate whether feasible varicella immunization paths that are optimal in controlling both varicella and zoster exist. We analyse the optimality system numerically focusing on the role of the cost functional, of the relative zoster-varicella cost and of the planning horizon length. We show that optimal programmes will mostly be unfeasible for public health owing to their complex temporal profiles. This complexity is the consequence of the intrinsically antagonistic nature of varicella immunization programmes when aiming to control both varicella and zoster. However, we show that gradually increasing-hence feasible-vaccination schedules can perform better than routine programmes with constant vaccine uptake. Finally, we show the optimal profiles of feasible programmes targeting mitigation of the post-immunization natural zoster boom with priority.

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Section: Discussionmentioning

confidence: 99%

Perspectives on optimal control of varicella and herpes zoster by mass routine varicella vaccination

et al. 2016

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“…Only a fraction of contacts that would result in varicella infection in susceptible individuals lead to an effective immune boosting in VZVexperienced individuals. After recovery from HZ, individuals are assumed to become lifelong immune to new episodes of VZV reactivation [11][12][13][14]. Indeed, secondary HZ episodes, although possible, are relatively rare in immunocompetent individuals [2].…”

Section: (B) the Modelmentioning

confidence: 99%

“…Mathematical models of VZV transmission dynamics, all based on the exogenous boosting hypothesis, unanimously predict that mass immunization against varicella, which has been already introduced in some countries [15,16], including some regions of Spain [17], may result in a temporary increase of HZ incidence [12,13,18,19] as a consequence of the expected reduction of VZV re-exposures after vaccination. Nonetheless, empirical evidence coming from surveillance programmes of HZ provides ambiguous results, with some studies showing an increase of HZ following mass immunization and others not [20,21].…”

Section: Introductionmentioning

confidence: 99%

The impact of demographic changes on the epidemiology of herpes zoster: Spain as a case study

et al. 2015

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Varicella zoster virus (VZV) causes varicella upon first exposure and may reactivate later in life into herpes zoster (HZ), with a risk that is thought to be reduced by re-exposures to VZV. Given the decades-long time scales of reactivation and its dependence on the accumulation of re-exposure episodes, adopting a long-term perspective may be useful to correctly interpret current epidemiological trends of VZV. In this study, we investigate the possible impact of demographic changes on varicella and HZ in Spain, using an agestructured mathematical model informed with historical demographic data and calibrated against age-specific profiles of varicella seroprevalence and HZ incidence data. The model qualitatively reproduces the remarkable growth of HZ incidence observed in Spain between 1997 and 2004, before the introduction of varicella vaccination programmes. We demonstrate that this growth may be partially ascribed to the reduction of varicella circulation that followed the overall decline of the birth rate in the twentieth century. Model predictions further suggest that, even under the most optimistic projections, HZ incidence will continue its rise until at least 2040. Considering the effect of demographic changes can help interpreting variations in epidemiological trends of HZ, contributing to a more accurate evaluation of vaccination programmes against VZV.

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“…This could be related to a temporal increase in the incidence of HZ, often occurring before the introduction of varicella vaccination programmes [11], as in Finland [11] and Germany [12]. In the United Kingdom, one study reported that the median age at HZ diagnosis was 62 years (interquartile range 48-73) [13].…”

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confidence: 99%

Herpes zoster vaccine: a shot to maintain wellbeing

Michel¹

2015

Aging Clin Exp Res

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The current era is full of contradictory vaccine issues. The emerging Ebola pandemic stimulates the world's citizens who are calling for the urgent development of vaccine to prevent the disease [1]. They seem to be suddenly remembering that vaccines represent a major advancement in public health [2]. While the complete eradication of polio, neonatal tetanus, congenital rubella, and measles are still the main targets in less developed countries [3], inhabitants of high-resource countries are focusing on rare adverse effects of vaccines to discredit the efficacy and effectiveness of vaccination. As a result, there is an increase in vaccine-preventable diseases in both children and adults. Indeed, it has been estimated that ten times more adults (40 to 50 thousand) die than children in the USA annually from potentially vaccine-preventable diseases [4].In this controversial context, alongside vaccines for lifethreatening diseases, there have emerged new vaccines to prevent the occurrence of diseases and their complications. Herpes zoster (HZ) vaccine [5][6][7], is the best example of such quality improvement vaccines. In this issue, Stefania Maggi and collaborators present a comprehensive and upto-date review of how the HZ vaccine improves healthy ageing [8]. This paper raises some questions concerning the global epidemiology of the disease, improved knowledge of HZ risk factors, the well-known and more surprising consequences of the disease, as well as the increasing dilemma about age and the new indications for the currently available vaccine.The incidence rate (IR) of HZ in Italy, at 6.3 per thousand person-years [8,9], is higher than the mean incidence rate of 3-5 per thousand person-years reported in an analysis of 130 studies conducted in 26 countries in North America, Europe, and Asia-Pacific [10]. This could be related to a temporal increase in the incidence of HZ, often occurring before the introduction of varicella vaccination programmes [11], as in Finland [11] and Germany [12]. In the United Kingdom, one study reported that the median age at HZ diagnosis was 62 years (interquartile range 48-73) [13]. The IR was more or less stable between the ages of 10 and 44 years (at around 2.4 per thousand personyears), but increased more than threefold, to reach 15 in the 80-84 year old age group [12]. In the same study population, the IR was 36 % higher in females than in males [12]. Prodromic pain was experienced by 69.5 % of South Korean patients, of whom 95.1 % had moderate-to-severe pain [14]. In Italy, postherpetic neuralgia (PHN) occurred in 20.6 and 9.2 % of HZ patients older than 50 years after 3 and 6 months respectively [8,15], which corresponds to the mean 6-month PHN risk reported in the world literature [16].The risk factors for HZ have recently been better identified, and Maggi's paper describes them in detail [8]. However, it is important to insist on a few of these factors. In a study cohort of 144,959 adults diagnosed with herpes zoster between 2000 and 2011, severely immunosuppressive conditions r...

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Perspectives on the Impact of Varicella Immunization on Herpes Zoster. A Model-Based Evaluation from Three European Countries

Cited by 69 publications

References 56 publications

Perspectives on optimal control of varicella and herpes zoster by mass routine varicella vaccination

Perspectives on optimal control of varicella and herpes zoster by mass routine varicella vaccination

The impact of demographic changes on the epidemiology of herpes zoster: Spain as a case study

Herpes zoster vaccine: a shot to maintain wellbeing

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