Public health management of antiviral drugs during the 2009 H1N1 influenza pandemic: a survey of local health departments in California

BACKGROUND

The large-scale deployment of antiviral drugs from the Strategic National Stockpile during the 2009 H1N1 influenza response provides a unique opportunity to study local public health implementation of the medical countermeasure dispensing capability in a prolonged event of national significance. This study aims to describe the range of methods used by local health departments (LHDs) in California to manage antiviral activities and to gain a better understanding of the related challenges experienced by health departments and their community partners.

METHODS

This research employed a mixed-methods approach. First, a multi-disciplinary focus group of pandemic influenza planners from key stakeholder groups in California was convened in order to generate ideas and identify critical themes related to the local implementation of antiviral activities during the H1N1 influenza response. These qualitative data informed the development of a web-based survey, which was distributed to all 61 LHDs in California for the purpose of assessing the experiences of a representative sample of local health agencies in a large region.

RESULTS

Forty-four LHDs participated in this study, representing 72% of the local public health agencies in California. While most communities dispensed a modest number of publicly purchased antivirals, LHDs nevertheless drew on their previous work and engaged in a number of antiviral activities, including: acquiring, allocating, distributing, dispensing, tracking, developing guidance, and communicating to the public and clinical community. LHDs also identified specific antiviral challenges presented by the H1N1 pandemic, including: reconciling multiple sources and versions of antiviral guidance, determining appropriate uses and recipients of publicly purchased antivirals, and staffing shortages.

CONCLUSIONS

The 2009 H1N1 influenza pandemic presented an unusual opportunity to learn about the role of local public health in the management of antiviral response activities during a real public health emergency. Results of this study offer an important descriptive account of LHD management of publicly purchased antivirals, and provide practitioners, policy makers, and academics with a practice-based assessment of these events. The issues raised and the challenges faced by LHDs should be leveraged to inform public health planning for future pandemics and other emergency events that require medical countermeasure dispensing activities.

Public perceptions of pandemic influenza resource allocation: a deliberative forum using Grid/Group analysis

The emergence of virulent avian influenza A subtypes with potential to evolve into novel human subtypes prompted directives from the World Health Organisation recommending that countries prepare for a pandemic. In response the Australian government developed the Australian Health Management Plan for Pandemic Influenza (AHMPPI), which includes strategies to contain and/or manage a pandemic. To implement these strategies successfully, community compliance is necessary. Our qualitative study investigated, through a deliberative forum, the extent to which the antiviral drug and vaccine allocation of the AHMPPI corresponds with community views about the priority groups. We used Mary Douglas' Grid/Group analysis to analyse the results, which suggested that the AHMPPI's allocation strategy corresponds well with community views with both based on a hierarchical structure. There are some differences concerning community involvement in the decision process and information provision to the public, for which our study provides recommendations.

Economic and social impact of influenza mitigation strategies by demographic class

BACKGROUND

We aim to determine the economic and social impact of typical interventions proposed by the public health officials and preventive behavioral changes adopted by the private citizens in the event of a "flu-like" epidemic.

METHOD

We apply an individual-based simulation model to the New River Valley area of Virginia for addressing this critical problem. The economic costs include not only the loss in productivity due to sickness but also the indirect cost incurred through disease avoidance and caring for dependents.

RESULTS

The results show that the most important factor responsible for preventing income loss is the modification of individual behavior; it drops the total income loss by 62% compared to the base case. The next most important factor is the closure of schools which reduces the total income loss by another 40%.

CONCLUSIONS

The preventive behavior of the private citizens is the most important factor in controlling the epidemic.

Diagnosis and antiviral intervention strategies for mitigating an influenza epidemic

BACKGROUND

Many countries have amassed antiviral stockpiles for pandemic preparedness. Despite extensive trial data and modelling studies, it remains unclear how to make optimal use of antiviral stockpiles within the constraints of healthcare infrastructure. Modelling studies informed recommendations for liberal antiviral distribution in the pandemic phase, primarily to prevent infection, but failed to account for logistical constraints clearly evident during the 2009 H1N1 outbreaks. Here we identify optimal delivery strategies for antiviral interventions accounting for logistical constraints, and so determine how to improve a strategy's impact.

METHODS AND FINDINGS

We extend an existing SEIR model to incorporate finite diagnostic and antiviral distribution capacities. We evaluate the impact of using different diagnostic strategies to decide to whom antivirals are delivered. We then determine what additional capacity is required to achieve optimal impact. We identify the importance of sensitive and specific case ascertainment in the early phase of a pandemic response, when the proportion of false-positive presentations may be high. Once a substantial percentage of ILI presentations are caused by the pandemic strain, identification of cases for treatment on syndromic grounds alone results in a greater potential impact than a laboratory-dependent strategy. Our findings reinforce the need for a decentralised system capable of providing timely prophylaxis.

CONCLUSIONS

We address specific real-world issues that must be considered in order to improve pandemic preparedness policy in a practical and methodologically sound way. Provision of antivirals on the scale proposed for an effective response is infeasible using traditional public health outbreak management and contact tracing approaches. The results indicate to change the transmission dynamics of an influenza epidemic with an antiviral intervention, a decentralised system is required for contact identification and prophylaxis delivery, utilising a range of existing services and infrastructure in a "whole of society" response.

Investment in antiviral drugs: a real options approach

Real options analysis is a promising approach to model investment under uncertainty. We employ this approach to value stockpiling of antiviral drugs as a precautionary measure against a possible influenza pandemic. Modifications of the real options approach to include risk attitude and deviations from expected utility are presented. We show that risk aversion counteracts the tendency to delay investment for this case of precautionary investment, which is in contrast to earlier applications of risk aversion to real options analysis. Moreover, we provide a numerical example using real world data and discuss the implications of real options analysis for health policy. Suggestions for further extensions of the model and a comparison with the expected value of information analysis are put forward.

Antiviral distribution data--a potential syndromic surveillance system to assist pandemic health service operational planning

A pilot study was conducted in rural northern New South Wales from 15 July to 28 August 2009, during Australia's Protect Phase response to the Influenza A H1N1 California 7/09 pandemic. This study explored the feasibility of using administrative data, generated from the distribution of stockpiled antivirals, as a syndromic surveillance system. The purpose was to identify recently affected towns or those with increasing influenza-like illness activity to assist in rural health service operational planning. Analysis of antiviral distribution data was restricted to 113 general practices in rural parts of the Hunter New England Area Health Service. By 2 September 2009 a total of 6,670 courses of antivirals for adults, of which 455 courses were replacement orders, had been distributed to these general practices. Distribution of replacement antivirals were mapped to local government areas on a weekly basis. The syndromic surveillance system delivered timely data on antiviral distribution; used readily available software to generate visual activity maps in less than 30 minutes; proved adaptable; was of low cost; and was well received by health service planners. Full evaluation of the system's utility was limited by the relatively large initial distribution of antivirals and the brief nature of Australia's first pandemic wave. The pilot study demonstrated that a syndromic surveillance system based on distribution of supplies, such as treatment or vaccines, can support local health service operational planning during health emergencies.

Tecovirimat, a p37 envelope protein inhibitor for the treatment of smallpox infection

Since the eradication of naturally occurring smallpox in 1980, the fear that variola virus could be used as a biological weapon has become real. Over the last 10 years, emergency preparedness programs have been launched to protect populations against a smallpox outbreak or the possible emergence in humans of other orthopoxvirus infections, such as monkeypox. Vaccination against smallpox was responsible for its eradication, but was linked with high rates of adverse events and contraindications. In this context, intensive research in the poxvirus field has led to the development of safer vaccines and to an increase in the number of anti-poxvirus agents in the pipeline. SIGA Technologies Inc, under license from ViroPharma Inc, is developing tecovirimat (ST-246). Tecovirimat is a novel antiviral that inhibits the egress of orthopoxviruses by targeting viral p37 protein orthologs. The development of tecovirimat during the last 5 years for the treatment of smallpox and for its potential use as adjunct to smallpox vaccine is reviewed here.

Oseltamivir compounding in the hospital pharmacy during the (H1N1) influenza pandemic

AIMS

Pandemics impose large demands on the health care system. The supply of appropriate chemotherapeutic agents, namely oseltamivir solution, presented a serious challenge in the recent influenza pandemic. This study reports on the rational series of pharmacotechnical steps that were followed to appropriately handle bulk oseltamivir powder to meet the increased demand.

METHODS

During a six-week period in August and September of 2009, a task force was created in the Central Pharmacy of Hospital das Clínicas to convert imported oseltamivir phosphate into ready-to-use solution for utilization by physicians and public health authorities. The protocol included dissolution, physico-chemical tests and the bottling of a liquid microdose formulation for emergency room and outpatient dispensing with adequate quality control during all phases.

RESULTS

The successful production routine was based on a specially designed flowchart according to which a batch of 33210 g of oseltamivir powder was converted into 32175 solution units during the aforementioned period with a net loss of only 2.6%. The end products were bottles containing 50 ml of 15 mg/mL oseltamivir solution. The measured concentration was stable and accurate (97.5% - 102.0% of the nominal value). The drug was prescribed as both a prophylactic and therapeutic agent.

DISCUSSION

Hospital pharmacies are conventionally engaged in the manipulation of medical prescriptions and specialty drugs. They are generally responsible for only small-scale equipment used for manufacturing and quality-control procedures. The compounding of oseltamivir was a unique effort dictated by exceptional circumstances.

CONCLUSION

The shortage of oseltamivir solution for clinical use was solved by emergency operationalization of a semi-industrial process in which bulk powder was converted into practical vials for prompt delivery.

Ethical guidelines in pandemic influenza: recommendations of the Ethics Subcommittee of the Advisory Committee of the Director, Centers for Disease Control and Prevention

Because of the importance of including ethical considerations in planning efforts for pandemic influenza, in February 2005 the Centers for Disease Control and Prevention requested that the Ethics Subcommittee of the Advisory Committee to the Director develop guidance that would serve as a foundation for decision making in preparing for and responding to pandemic influenza. Specifically, the ethics subcommittee was asked to make recommendations regarding ethical considerations relevant to decision making about vaccine and antiviral drug distribution prioritization and development of interventions that would limit individual freedom and create social distancing. The ethics subcommittee identified a number of general ethical considerations including identification of clear goals for pandemic planning, responsibility to maximize preparedness, transparency and public engagement, sound science, commitment to the global community, balancing individual liberty and community interests, diversity in ethical decision making, and commitment to justice. These general ethical considerations are applied to the issues of vaccine and antiviral drug distribution and use of community mitigation interventions.

Can we "hedge" against the development of antiviral resistance among pandemic influenza viruses?

David K. Shay and Benjamin Ridenhour discuss a modeling study predicting that stockpiling a secondary antiviral for use early in a flu pandemic can forestall resistance to the primary stockpiled drug.

Hedging against antiviral resistance during the next influenza pandemic using small stockpiles of an alternative chemotherapy

BACKGROUND

The effectiveness of single-drug antiviral interventions to reduce morbidity and mortality during the next influenza pandemic will be substantially weakened if transmissible strains emerge which are resistant to the stockpiled antiviral drugs. We developed a mathematical model to test the hypothesis that a small stockpile of a secondary antiviral drug could be used to mitigate the adverse consequences of the emergence of resistant strains.

METHODS AND FINDINGS

We used a multistrain stochastic transmission model of influenza to show that the spread of antiviral resistance can be significantly reduced by deploying a small stockpile (1% population coverage) of a secondary drug during the early phase of local epidemics. We considered two strategies for the use of the secondary stockpile: early combination chemotherapy (ECC; individuals are treated with both drugs in combination while both are available); and sequential multidrug chemotherapy (SMC; individuals are treated only with the secondary drug until it is exhausted, then treated with the primary drug). We investigated all potentially important regions of unknown parameter space and found that both ECC and SMC reduced the cumulative attack rate (AR) and the resistant attack rate (RAR) unless the probability of emergence of resistance to the primary drug p(A) was so low (less than 1 in 10,000) that resistance was unlikely to be a problem or so high (more than 1 in 20) that resistance emerged as soon as primary drug monotherapy began. For example, when the basic reproductive number was 1.8 and 40% of symptomatic individuals were treated with antivirals, AR and RAR were 67% and 38% under monotherapy if p(A) = 0.01. If the probability of resistance emergence for the secondary drug was also 0.01, then SMC reduced AR and RAR to 57% and 2%. The effectiveness of ECC was similar if combination chemotherapy reduced the probabilities of resistance emergence by at least ten times. We extended our model using travel data between 105 large cities to investigate the robustness of these resistance-limiting strategies at a global scale. We found that as long as populations that were the main source of resistant strains employed these strategies (SMC or ECC), then those same strategies were also effective for populations far from the source even when some intermediate populations failed to control resistance. In essence, through the existence of many wild-type epidemics, the interconnectedness of the global network dampened the international spread of resistant strains.

CONCLUSIONS

Our results indicate that the augmentation of existing stockpiles of a single anti-influenza drug with smaller stockpiles of a second drug could be an effective and inexpensive epidemiological hedge against antiviral resistance if either SMC or ECC were used. Choosing between these strategies will require additional empirical studies. Specifically, the choice will depend on the safety of combination therapy and the synergistic effect of one antiviral in suppressing the emergence of resistance to the other antiviral when both are taken in combination.