Varicella-zoster virus vaccination under the exogenous boosting hypothesis: two ethical perspectives

Seroprevalence of varicella-zoster virus antibody and immunogenicity of live attenuated varicella vaccine in healthcare workers in Taiwan

BACKGROUND

Healthcare workers (HCWs) without evidence of immunity to varicella-zoster virus (VZV) are recommended to undergo varicella vaccination. Immunogenicity of live attenuated varicella vaccine has rarely been investigated among HCWs in Taiwan.

METHODS

Anti-VZV immunoglobulin G (IgG) titer was checked for all HCWs at Changhua Christian Hospital from 2011 to 2017. One-dose and two-dose (separated by 4-8 weeks) vaccines were administered to HCWs with equivocal and negative anti-varicella IgG results, respectively. Follow-up anti-VZV IgG was determined at least 4 weeks after completion of vaccination. Factors associated with seroconversion to varicella vaccination were analyzed.

RESULTS

Among 2406 included HCWs, the anti-VZV IgG serostatus was tested positive, equivocal and negative in 1924 (79.9%), 117 (4.9%) and 365 (15.2%), respectively. The seroprevalence had decreased from 88.0% (235/267) in 2011 to 72.2% (270/374) in 2017 (p for trend <0.05). A total of 67.8% (327/482) HCWs completed scheduled vaccination and serological follow-up. The seroconversion rates for HCWs with baseline equivocal and negative anti-VZV IgG results were 100% (80/80) and 79.4% (196/247) after one- and two-dose vaccination, respectively. In multivariate analysis, obesity (adjusted odds ratio, 0.308; 95% confidence interval [CI], 0.11-0.94, p = 0.039) was the only factor statistically significantly associated with seroconversion to vaccination.

CONCLUSION

Decreasing trends of seroprevalence of VZV were observed among HCWs from 2011 to 2017. HCWs who were obese were less likely to respond to varicella vaccination.

Economic Evaluation of Vaccines: Belgian Reflections on the Need for a Broader Perspective

OBJECTIVES

The standard framework of economic evaluation of health programs, which is increasingly used for policy funding decisions, is insufficiently equipped to reflect the full range of health and economic benefits conferred by vaccines and thus undervalues vaccination.

METHODS

In 2019, a group of Belgian health economic and clinical experts, supported by 2 senior international vaccination experts (1 American, 1 Belgian), convened 4 roundtable meetings to highlight which particular value elements of vaccination remain neglected in economic evaluations.

RESULTS

They concluded that the standard economic evaluation framework fails to reflect the full value of vaccination with respect to prevention of complications linked to some vaccine-preventable diseases, health gains for caregivers, herd effects, changes in exposure to and distribution of serotypes, the effect on antimicrobial resistance, productivity gains for caregivers and patients, and the distributive implications of vaccination programs.

CONCLUSIONS

Here, suggestions are made regarding how these shortcomings can be addressed in future economic evaluations of vaccines and how a more level playing field between vaccines and other health programs can be created.

Integrating Alternative Social Value Judgments Into Cost-Effectiveness Analysis of Vaccines: An Application to Varicella-Zoster Virus Vaccination

OBJECTIVES

Cost-effectiveness analyses (CEA) are based on the value judgment that health outcomes (eg, quantified in quality-adjusted life-years; QALYs) are all equally valuable irrespective of their context. Whereas most published CEAs perform extensive sensitivity analysis on various parameters and assumptions, only rarely is the influence of the QALY-equivalence assumption on cost-effectiveness results investigated. We illustrate how the integration of alternative social value judgments in CEA can be a useful form of sensitivity analysis.

METHODS

Because varicella-zoster virus (VZV) vaccination affects 2 distinct diseases (varicella zoster and herpes zoster) and likely redistributes infections across different age groups, the program has an important equity dimension. We used a cost-effectiveness model and disentangled the share of direct protection and herd immunity within the total projected QALYs resulting from a 50-year childhood VZV program in the UK. We use the UK population's preferences for QALYs in the vaccine context to revalue QALYs accordingly.

RESULTS

Revaluing different types of QALYs for different age groups in line with public preferences leads to a 98% change in the projected net impact of the program. The QALYs gained among children through direct varicella protection become more important, whereas the QALYs lost indirectly through zoster in adults diminish in value. Weighting of vaccine-related side effects made a large difference.

CONCLUSIONS

Our study shows that a sensitivity analysis in which alternative social value judgments about the value of health outcomes are integrated into CEA of vaccines is relatively straightforward and provides important additional information for decision makers to interpret cost-effectiveness results.

Pox Parties for Grannies? Chickenpox, Exogenous Boosting, and Harmful Injustices

Some societies tolerate or encourage high levels of chickenpox infection among children to reduce rates of shingles among older adults. This tradeoff is unethical. The varicella zoster virus (VZV) causes both chickenpox and shingles. After people recover from chickenpox, VZV remains in their nerve cells. If their immune systems become unable to suppress the virus, they develop shingles. According to the Exogenous Boosting Hypothesis (EBH), a person's ability to keep VZV suppressed can be 'boosted' through exposure to active chickenpox infections. We argue that even if this hypothesis were true, immunization policies that discourage routine childhood varicella vaccination in order to prevent shingles for other people are unethical. Such policies harm children and treat them as mere means for the benefit of others, and are inconsistent with how parents should treat their children and physicians should treat their patients. These policies also seem incompatible with institutional transparency.

Quantifying the public's view on social value judgments in vaccine decision-making: A discrete choice experiment

Vaccination programs generate direct protection, herd protection and, occasionally, side effects, distributed over different age groups. This study elicits the general public's view on how to balance these outcomes in funding decisions for vaccines. We performed an optimal design discrete choice experiment with partial profiles in a representative sample (N = 1499) of the population in the United Kingdom in November 2016. Using a panel mixed logit model, we quantified, for four different types of infectious disease, the importance of a person's age during disease, how disease was prevented-via direct vaccine protection or herd protection-and whether the vaccine induced side effects. Our study shows clear patterns in how the public values vaccination programs. These diverge from the assumptions made in public health and cost-effectiveness models that inform decision-making. We found that side effects and infections in newborns and children were of primary importance to the perceived value of a vaccination program. Averting side effects was, in any age group, weighted three times as important as preventing an identical natural infection in a child whereas the latter was weighted six times as important as preventing the same infection in elderly aged 65-75 years. These findings were independent of the length or severity of the disease, and were robust across respondents' backgrounds. We summarize these patterns in a set of preference weights that can be incorporated into future models. Although the normative significance of these weights remains a matter open for debate, our study can, hopefully, contribute to the evaluation of vaccination programs beyond cost-effectiveness.

Post-herpetic neuralgia - a review of current management and future directions

Post-herpetic neuralgia (PHN) is common and treatment is often suboptimal with less than half of patients achieving adequate 50% pain relief. As an area of unmet clinical need and as an archetype of neuropathic pain, it deserves the attention of clinicians and researchers. Areas covered: This review summarises the epidemiology, pathophysiology, risk factors and clinical features of varicella infection. It describes the current and possible future management strategies for preventing varicella infection and reactivation and for treating PHN. Expert opinion: A highly successful Varicella Zoster (VZV) vaccine has not been universally adopted due to fears that it may increase Herpes Zoster (HZ) incidence - and thus PHN - in older, unvaccinated generations. This is a controversial theory but advances in the efficacy of vaccines against HZ may allay these fears and encourage more widespread adoption of the VZV vaccine. Treatment of PHN, as for any neuropathic pain, must be multidisciplinary and multimodal. Advances in sensory phenotyping technology and genomics may allow more individualised treatment. Traditional research methodologies are ill-suited to assess the kind of complex interventions that are necessary to achieve better clinical outcomes in this challenging field.

Varicella vaccination - the global experience

INTRODUCTION

Varicella, although a frequently benign childhood disease, nevertheless represents a considerable health burden. WHO recommends including varicella vaccines in universal routine vaccination programs, and maintaining coverage >80%. Many countries have successfully introduced varicella vaccination and have benefited from lower disease burden, but many others have not adopted the vaccine. Reasons include cost commitment for a 'mild childhood disease' or concerns that vaccination will shift varicella to older age groups or increase herpes zoster incidence. Areas covered: This literature review summarizes the effectiveness and epidemiological impact of varicella immunization programs. Expert commentary: Varicella vaccines are immunogenic with acceptable safety profiles. One and two dose schedules are highly effective against varicella and large reductions in disease incidence, particularly moderate-severe disease, have been widely reported. There is currently no evidence to suggest that the introduction of varicella vaccination results in a shift of varicella disease burden to older age groups. Although epidemiological studies have shown an increased incidence of herpes zoster since the vaccines were launched, there are many other contributing factors, and indeed, this secular trend was evident before their introduction. In conclusion, varicella vaccination easily fits into existing immunization programs and significantly reduces the often underestimated burden of varicella.

The Social Value Of Vaccination Programs: Beyond Cost-Effectiveness

In the current global environment of increased strain on health care budgets, all medical interventions have to compete for funding. Cost-effectiveness analysis has become a standard method to use in estimating how much value an intervention offers relative to its costs, and it has become an influential element in decision making. However, the application of cost-effectiveness analysis to vaccination programs fails to capture the full contribution such a program offers to the community. Recent literature has highlighted how cost-effectiveness analysis can neglect the broader economic impact of vaccines. In this article we also argue that socioethical contributions such as effects on health equity, sustaining the public good of herd immunity, and social integration of minority groups are neglected in cost-effectiveness analysis. Evaluations of vaccination programs require broad and multidimensional perspectives that can account for their social, ethical, and economic impact as well as their cost-effectiveness.

Efficacy of varicella (VZV) vaccination: an update for the clinician

Varicella-zoster virus (VZV) infection causes two distinct clinical conditions. Primary varicella infection results in chickenpox, a contagious rash illness typically seen among children. VZV can reactivate years after the initial infection to cause herpes zoster (HZ) and lead to post-herpetic neuralgia, a common complication resulting in persistent pain that may last for years after the zoster rash resolves. A person's risk of having longer lasting and more severe pain associated with HZ increases with age. Since the introduction of VZV vaccines, the rates of infection, hospitalizations, and mortality have declined. In this review, we discuss in detail current VZV vaccines available for the prevention of VZV and HZ infections. Varilrix (GSK Biologicals, UK), Varivax (Merck, USA) and the combined measles, mumps, rubella, and varicella (MMRV) vaccine contain the live attenuated Oka strain of VZV for routine varicella vaccination. While Zostavax is the only HZ vaccine currently approved for use in the United States and the European Union [EMEA, 2011], a subunit vaccine candidate called HZ/su has recently shown improved efficacy for zoster prevention in two clinical trial phase III studies. VariZIG, a post-exposure prophylactic, uses zoster immune globulin to prevent VZV infection in those who have recently been in contact with VZV but lack evidence of varicella immunity and are contraindicated to receive the varicella vaccine. Further, we discuss the skin tropic and neurotropic factor VZV ORF7 gene and its involvement in varicella infection, reactivation and latency in ganglia. Ultimately, these studies can contribute to the development of a neuroattenuated vaccine candidate against varicella or a vector for delivery of other virus antigens.