Nancy Thiry

Bio: Nancy Thiry is an academic researcher from University of Antwerp. The author has contributed to research in topics: Vaccination & Cost effectiveness. The author has an hindex of 8, co-authored 13 publications receiving 382 citations.

Economic evaluations of varicella vaccination programmes: a review of the literature

Abstract: Chickenpox infections are generally mild but due to their very high incidence among healthy children they give rise to considerable morbidity and occasional mortality. With the development of a varicella vaccine in the early 1970s and its progressive licensing in many countries, interest in the efficiency of varicella immunisation programmes grew. The objective of this review was to discuss the methodological aspects and results of published economic evaluations of varicella vaccination. From this, we attempted to make recommendations. A computerised search was carried out; 17 full economic evaluations of varicella vaccination were retrieved. The review identified the methodological divergences and similarities between the articles in four areas: study design, epidemiological data, economic data and model characteristics. We assessed to what extent the applied methods conform to general guidelines for the economic evaluation of healthcare interventions and compared the studies' results. The desirability of a universal vaccination programme depends on whose perspective is taken. Despite variability in data and model assumptions, the studies suggest that universal vaccination of infants is attractive to society because large savings occur from averted unproductive days for parents. For the healthcare payer, universal vaccination of infants does not generate savings. Vaccination of susceptible adolescents has been proposed by some authors as a viable alternative; the attractiveness of this is highly dependent on the negative predictive value of anamnestic screening. Targeted vaccination of healthcare workers and immunocompromised individuals appears relatively cost effective. Findings for other target groups are either contradictory or provide insufficient evidence for any unequivocal recommendations to be made. High sensitivity to vaccine price was reported in most studies. This review highlights that some aspects of these studies need to be further improved before final recommendations can be made. First, more transparency, completeness and compliance to general methodological guidelines are required. Second, because of the increasing severity of varicella with age, it is preferable and in some cases essential to use dynamic models for the assessment of universal vaccination strategies. Third, most studies focused on the strategy of vaccinating children only while their results depended heavily on disputable assumptions (regarding vaccine effectiveness and impact on herpes zoster). Since violation of these assumptions could have important adverse public health effects, we suggest pre-adolescent vaccination as a more secure alternative. This option deserves more attention in future analyses.

Varicella vaccination in Europe: are we ready for a universal childhood programme?

Abstract: Safe and effective vaccines against varicella zoster virus (VZV), the aetiological agent of varicella and shingles, have been available in Europe for the last 5–10 years. The USA has had a universal childhood vaccination policy since 1995 and this has resulted in a dramatic decrease in the incidence, morbidity and mortality related to varicella. The economic and medical burden of VZV has led to discussions regarding both the desirability and feasability of a similar routine immunisation policy for all European children. This article examines the epidemiology of varicella in Europe and how the data emerging from the USA can be used to achieve adequate prevention of the disease. It looks into the current evidence of the health economic evaluation of universal varicella vaccination and explores the concerns surrounding such a policy, including the postulated impact on the incidence of zoster. In conclusion, the Society of Independent European Vaccination Experts (SIEVE) recommends that the immunisation of susceptible adolescents needs to be urgently implemented, in addition to the current recommendations targeting high-risk patients, their close contacts with a negative history of varicella and seronegative health-care workers. A universal policy, optimally incorporating a two-dose schedule, will be needed to finally reduce the burden of disease of varicella from a societal point of view. The SIEVE recommends the implementation of such a policy as soon as financially and practically possible.

The seroepidemiology of primary varicella-zoster virus infection in Flanders (Belgium).

Abstract: The age-specific seroprevalence of varicella-zoster virus (VZV) antibodies was assessed in a sample of the Flemish (Belgian) population. ELISA tests were used to analyse 1673 sera from subjects aged 1 to 44 years (October 1999 – April 2000). Chickenpox infections in Flanders appear to affect children at a younger age than in other European countries since 47.37% (95% CI: 37.33–57.41) is already immune at 2 years of age. For older age-groups, the prevalence is similar to that of most European countries: 80.19% (95% CI: 72.60–87.78) at 5 years, 92.52% (95% CI: 87.54–97.51) at 9 years and 100%≥40 years. The accuracy of non-positive recollections of varicella histories among Flemish 10 to 17-year olds was examined on the basis of a second (residual) serum bank. In this group, VZV seroprevalence was almost always 100% (or nearly 100%), irrespective of age, degree of reliability (negative or uncertain answers) or level of ascertainment (child personally or parents). The limited size of this second data set did not allow for an accurate assessment of the negative predictive value of such recollections. Conclusion: since varicella-zoster virus predominantly affects very small children and is generally perceived as benign, the required high coverage rate of a universal childhood varicella vaccination programme may be hard to attain. Adolescent strategies can minimise the population risks involved but the accuracy of non positive antecedents of chickenpox needs to be documented to assess the efficiency of such strategies.

The neurotropic herpes viruses: herpes simplex and varicella-zoster

Abstract: Summary Herpes simplex viruses types 1 and 2 (HSV1 and HSV2) and varicella-zoster virus (VZV) establish latent infection in dorsal root ganglia for the entire life of the host. From this reservoir they can reactivate to cause human morbidity and mortality. Although the viruses vary in the clinical disorders they cause and in their molecular structure, they share several features that affect the course of infection of the human nervous system. HSV1 is the causative agent of encephalitis, corneal blindness, and several disorders of the peripheral nervous system; HSV2 is responsible for meningoencephalitis in neonates and meningitis in adults. Reactivation of VZV, the pathogen of varicella (chickenpox), is associated with herpes zoster (shingles) and central nervous system complications such as myelitis and focal vasculopathies. We review the biological, medical, and neurological aspects of acute, latent, and reactivated infections with the neurotropic herpes viruses.

Varicella zoster virus infection.

Abstract: Infection with varicella zoster virus (VZV) causes varicella (chickenpox), which can be severe in immunocompromised individuals, infants and adults. Primary infection is followed by latency in ganglionic neurons. During this period, no virus particles are produced and no obvious neuronal damage occurs. Reactivation of the virus leads to virus replication, which causes zoster (shingles) in tissues innervated by the involved neurons, inflammation and cell death - a process that can lead to persistent radicular pain (postherpetic neuralgia). The pathogenesis of postherpetic neuralgia is unknown and it is difficult to treat. Furthermore, other zoster complications can develop, including myelitis, cranial nerve palsies, meningitis, stroke (vasculopathy), retinitis, and gastroenterological infections such as ulcers, pancreatitis and hepatitis. VZV is the only human herpesvirus for which highly effective vaccines are available. After varicella or vaccination, both wild-type and vaccine-type VZV establish latency, and long-term immunity to varicella develops. However, immunity does not protect against reactivation. Thus, two vaccines are used: one to prevent varicella and one to prevent zoster. In this Primer we discuss the pathogenesis, diagnosis, treatment, and prevention of VZV infections, with an emphasis on the molecular events that regulate these diseases. For an illustrated summary of this Primer, visit: http://go.nature.com/14xVI1.

Effect of Pneumococcal Conjugate Vaccination on Serotype-Specific Carriage and Invasive Disease in England: A Cross-Sectional Study

Abstract: We investigated the effect of the 7-valent pneumococcal conjugate vaccine (PCV7) programme in England on serotype-specific carriage and invasive disease to help understand its role in serotype replacement and predict the impact of higher valency vaccines Nasopharyngeal swabs were taken from children <5 y old and family members (n = 400) 2 y after introduction of PCV7 into routine immunization programs Proportions carrying Streptococcus pneumoniae and serotype distribution among carried isolates were compared with a similar population prior to PCV7 introduction Serotype-specific case:carrier ratios (CCRs) were estimated using national data on invasive disease In vaccinated children and their contacts vaccine-type (VT) carriage decreased, but was offset by an increase in non-VT carriage, with no significant overall change in carriage prevalence, odds ratio 106 (95% confidence interval 076–149) The lower CCRs of the replacing serotypes resulted in a net reduction in invasive disease in children The additional serotypes covered by higher valency vaccines had low carriage but high disease prevalence Serotype 11C emerged as predominant in carriage but caused no invasive disease whereas 8, 12F, and 22F emerged in disease but had very low carriage prevalence Because the additional serotypes included in PCV10/13 have high CCRs but low carriage prevalence, vaccinating against them is likely to significantly reduce invasive disease with less risk of serotype replacement However, a few serotypes with high CCRs could mitigate the benefits of higher valency vaccines Assessment of the effect of PCV on carriage as well as invasive disease should be part of enhanced surveillance activities for PCVs