Modeling mitigation of influenza epidemics by baloxavir

Willingness to pay for the effect of SARS-CoV-2 antivirals in preventing COVID-19 transmission to others in the Japanese population

OBJECTIVE

This study aimed to investigate the willingness to pay (WTP) of the Japanese population for the transmission prevention function of SARS-CoV-2 antiviral treatments and identify the attributes associated with higher WTP.

METHODS

A web-based survey (registration number: UMIN000054955) was conducted from May 17 to June 1, 2024, targeting a general population using a survey company panel. We aimed to obtain around 3,000 valid responses. Respondents were randomly divided into two groups: one assuming a COVID-19 infection (infection-assumed group) and the other without this assumption (non-infection-assumed group). WTP was assessed using an open-ended question format, asking how much they would be willing to pay out-of-pocket for a hypothetical antiviral drug that reduces the risk of transmitting COVID-19 to others by half. The survey also collected demographic information, COVID-19 related attributes, empathy levels using the Multidimensional Empathy Scale (MES), and health literacy using the Communicative and Critical Health Literacy scale. The mean WTP for COVID-19 treatment was calculated for all respondents and for the infection-assumed and non-infection-assumed groups. Subgroup analyses examined the effects of respondent attributes on WTP. A linear regression model with stepwise selection identified factors associated with WTP.

RESULTS

Responses were obtained from 3,657 individuals, with 3,131 valid responses analyzed. The mean WTP among all respondents was JPY 3,205 (USD 20.85) (standard error: JPY 84 [USD 0.55]). The infection-assumed group showed a 21% higher WTP than the non-infection-assumed group (p < 0.001). Subgroup analyses indicated that WTP varied based on attributes such as co-residing children, occupation, empathy levels, and health literacy. Higher WTP was significantly associated with being aged 65 years and older, higher household income, absence of co-residing children, being a company employee, executive, or public servant, fear of COVID-19 infection, higher other-oriented emotional reactivity (a factor of MES), and higher health literacy.

CONCLUSION

We presented the WTP of the Japanese population for the transmission prevention function of COVID-19 treatments as an actual monetary value. Factors such as empathy, health literacy, and some attributes were significantly associated with WTP. These findings might help inform policymakers in developing health policies based on the universal health insurance system in Japan.

Efficacy of Baloxavir Treatment in Preventing Transmission of Influenza

BACKGROUND

Baloxavir marboxil (baloxavir) rapidly reduces influenza virus shedding, which suggests that it may reduce transmission. Studies of treatment with neuraminidase inhibitors have not shown sufficient evidence that they prevent transmission to contacts.

METHODS

We conducted a multicountry, phase 3b trial to assess the efficacy of single-dose baloxavir treatment to reduce influenza transmission from index patients to household contacts. Influenza-positive index patients 5 to 64 years of age were randomly assigned in a 1:1 ratio to receive baloxavir or placebo within 48 hours after symptom onset. The primary end point was transmission of influenza virus from an index patient to a household contact by day 5. The first secondary end point was transmission of influenza virus by day 5 that resulted in symptoms.

RESULTS

Overall, 1457 index patients and 2681 household contacts were enrolled across the 2019-2024 influenza seasons; 726 index patients were assigned to the baloxavir group, and 731 to the placebo group. By day 5, transmission of laboratory-confirmed influenza was significantly lower with baloxavir than with placebo (adjusted incidence, 9.5% vs. 13.4%; adjusted odds ratio, 0.68; 95.38% confidence interval [CI], 0.50 to 0.93; P = 0.01), with an adjusted relative risk reduction of 29% (95.38% CI, 12 to 45). The adjusted incidence of transmission of influenza virus by day 5 that resulted in symptoms was 5.8% with baloxavir and 7.6% with placebo; however, the difference was not significant (adjusted odds ratio, 0.75; 95.38% CI, 0.50 to 1.12; P = 0.16). Emergence of drug-resistant viruses during the follow-up period occurred in 7.2% (95% CI, 4.1 to 11.6) of the index patients in the baloxavir group; no resistant viruses were detected in household contacts. No new safety signals were identified.

CONCLUSIONS

Treatment with a single oral dose of baloxavir led to a lower incidence of transmission of influenza virus to close contacts than placebo. (Funded by F. Hoffmann-La Roche and others; CENTERSTONE ClinicalTrials.gov number, NCT03969212.).

Stability of Respiratory Syncytial Virus in Nasal Aspirate From Patients Infected With RSV

BACKGROUND

Evaluation of infectious virus titer is a challenge for respiratory syncytial virus (RSV) clinical trials because of the labile nature of RSV and rapid loss of infectivity without proper specimen handling. However, there has been no rigorous investigation into RSV stability in clinical specimens.

METHODS

RSV stability was investigated by evaluating virus titers and defined as titer variation from baseline within three standard deviations of our titration assay. RSV stability in viral transport medium (VTM) at 4°C and the effect of freezing method on stability were evaluated using RSV-A2 stock. RSV stability in nasal aspirates collected in VTM at 4°C was estimated by regression analysis of virus titers measured at several time points. Stability of these specimens stored at -80°C for 10-15 months after freezing by the method, which maintained RSV-A2 stability, was also assessed.

RESULTS

Three standard deviations were calculated from our titration assay as 0.97 log10 50% tissue culture infectious dose (TCID50/mL), and RSV stability was defined as variation of virus titer from baseline within 1.0 log10TCID50/mL. RSV-A2 in VTM at 4°C was stable for at least 120 h. Freezing at -80°C negatively affected virus stability, whereas freezing in liquid nitrogen or a dry ice-ethanol bath did not. RSV in nasal aspirates was stable for 2 days at 4°C and for 10-15 months at -80°C after snap freezing.

CONCLUSIONS

RSV in nasal aspirates in VTM was estimated to be stable for 2 days at 4°C and for approximately 1 year at -80°C.

Modeling the Impact of Ensitrelvir on SARS-CoV-2 Dynamics and Its Application for Assessment of Transmission Mitigation of Patients with COVID-19

INTRODUCTION

Mathematical modeling can provide quantitative understanding of the viral dynamics and viral reduction effects of drugs and enable simulations of the dynamics in various scenarios. In this study, a drug effect model of ensitrelvir was developed to describe the viral reduction effect. Using the model, we also estimated the impact of treatment with ensitrelvir on the reduction in the number of infected patients at the population level in Japan.

METHODS

The drug effect model of ensitrelvir was developed based on a viral dynamic model for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and a population pharmacokinetic model of ensitrelvir using 10,477 samples of viral load from 1447 patients with coronavirus disease 2019 (COVID-19) in a phase 2/3 study. It was assumed that the drug effect on SARS-CoV-2 promoted the viral clearance depending on the free plasma concentrations. We estimated the impact of ensitrelvir treatment on the reduction in the number of infected patients at the population level in Japan using the susceptible-infectious-recovered-susceptible (SIRS) model including transmission mitigation.

RESULTS

The viral reduction effect of ensitrelvir was characterized as a promotion of viral clearance depending on the plasma ensitrelvir concentrations using the Emax model. The maximum reduction effect was considered to depend on the time from symptom onset to treatment. The maximum transmission mitigation effect was observed when treatment was initiated within 12-24 h of symptom onset, and secondary infections could be reduced by administering ensitrelvir as soon as possible after symptom onset.

CONCLUSION

The viral reduction by ensitrelvir could be characterized based on the viral dynamics, and the dynamics could be estimated using the drug effect model. Furthermore, the drug effect on population level transmission based on the dynamics could be estimated. Thus, the simulation could be conducted for various conditions.

Evaluating the Public Health and Health Economic Impacts of Baloxavir Marboxil and Oseltamivir for Influenza Pandemic Control in China: A Cost-Effectiveness Analysis Using a Linked Dynamic Transmission-Economic Evaluation Model

BACKGROUND

Pandemic influenza poses a recurring threat to public health. Antiviral drugs are vital in combating influenza pandemics. Baloxavir marboxil (BXM) is a novel agent that provides clinical and public health benefits in influenza treatment.

METHODS

We constructed a linked dynamic transmission-economic evaluation model combining a modified susceptible-exposed-infected-recovered (SEIR) model and a decision tree model to evaluate the cost-effectiveness of adding BXM to oseltamivir in China's influenza pandemic scenario. The cost-effectiveness was evaluated for the general population from the Chinese healthcare system perspective, although the users of BXM and oseltamivir were influenza-infected persons. The SEIR model simulated the transmission dynamics, dividing the population into four compartments: susceptible, exposed, infected, and recovered, while the decision tree model assessed disease severity and costs. We utilized data from clinical trials and observational studies in the literature to parameterize the models. Costs were based on 2021 CN¥ and not discounted due to a short time-frame of one year in the model. One-way, two-way, and probabilistic sensitivity analyses were also conducted.

RESULTS

The integrated model demonstrated that adding BXM to treatment choices reduced the cumulative incidence of infection from 49.49% to 43.26% and increased quality-adjusted life years (QALYs) by 0.00021 per person compared with oseltamivir alone in the base-case scenario. The intervention also amounted to a positive net monetary benefit of CN¥77.85 per person at the willingness to pay of CN¥80,976 per QALY. Sensitivity analysis confirmed the robustness of these findings, with consistent results across varied key parameters and assumptions.

CONCLUSIONS

Adding BXM to treatment choices instead of only treating with oseltamivir for influenza pandemic control in China appears to be cost-effective compared with oseltamivir alone. The dual-agent strategy not only enhances population health outcomes and conserves resources, but also mitigates influenza transmission and alleviates healthcare burden.

A cost-effectiveness analysis of reduced viral transmission with baloxavir marboxil versus oseltamivir or no treatment for seasonal and pandemic influenza management in the United Kingdom

BACKGROUND

Baloxavir marboxil is an oral, single-dose, cap-dependent endonuclease inhibitor that reduces the duration of influenza symptoms and rapidly stops viral shedding. We developed a susceptible, exposed, infected, recovered (SEIR) model to inform a cost-effectiveness model (CEM) of baloxavir versus oseltamivir or no antiviral treatment in the UK.

RESEARCH DESIGN AND METHODS

The SEIR model estimated the attack rates among otherwise healthy and high-risk individuals in seasonal and pandemic settings. The CEM assumed that a proportion of infected patients would receive antiviral treatment. Results were reported at the population level (per 10,000 at risk of infection).

RESULTS

The SEIR model estimated greater reductions in infections with baloxavir. In a seasonal setting, baloxavir provided incremental cost-effectiveness ratios (ICERs) of £1884 per quality-adjusted life-year (QALY) gained versus oseltamivir and a dominant cost-effectiveness position versus no antiviral treatment in the total population; ICERs of £2574/QALY versus oseltamivir and £128/QALY versus no antiviral treatment were seen in the high-risk population. Baloxavir was also cost-effective versus oseltamivir or no antiviral treatment and reduced population-level health system occupancy concerns during a pandemic.

CONCLUSION

Baloxavir treatment resulted in the fewest influenza cases and was cost-effective versus oseltamivir or no antiviral treatment from a UK National Health Service perspective.

Editorial: Infectious Disease Epidemiology and Transmission Dynamics 2.0

This Special Issue includes six original articles and one review article, all reflecting the unified scientific research endeavors and professional expertise for a shared objective, which were published between July 2023 and November 2023 [...].

Comparative Effectiveness of Baloxavir Marboxil and Oseltamivir Treatment in Reducing Household Transmission of Influenza: A Post Hoc Analysis of the BLOCKSTONE Trial

BACKGROUND

The transmission of influenza virus in households, especially by children, is a major route of infection. Prior studies suggest that timely antiviral treatment of ill cases may reduce infection in household contacts. The aim of the study was to compare the effects of oseltamivir (OTV) and baloxavir marboxil (BXM) treatment of index cases on the secondary attack rate (SAR) of influenza within household.

METHODS

A post hoc analysis was done in BLOCKSTONE trial-a placebo-controlled, double-blinded post-exposure prophylaxis of BXM. Data were derived from the laboratory-confirmed index cases' household contacts who received placebo in the trial and also from household members who did not participate in the trial but completed illness questionnaires. To assess the SAR of household members, multivariate analyses adjusted for factors including age, vaccination status, and household size were performed and compared between contacts of index cases treated with BXM or OTV.

RESULTS

In total, 185 index cases (116 treated with BXM and 69 treated with OTV) and 410 household contacts (201 from trial, 209 by questionnaire) were included. The Poisson regression modeling showed that the SAR in household contacts of index cases treated with BXM and OTV was 10.8% and 18.5%, respectively; the adjusted relative reduction in SAR was 41.8% (95% confidence interval: 1.0%-65.7%, p = 0.0456) greater with BXM than OTV. Similar reductions were found in contacts from the trial and those included by questionnaire.

CONCLUSION

BXM treatment of index cases appeared to result in a greater reduction in secondary household transmission than OTV treatment.

A retrospective cohort study of Paxlovid efficacy depending on treatment time in hospitalized COVID-19 patients

Paxlovid, a SARS-CoV-2 antiviral, not only prevents severe illness but also curtails viral shedding, lowering transmission risks from treated patients. By fitting a mathematical model of within-host Omicron viral dynamics to electronic health records data from 208 hospitalized patients in Hong Kong, we estimate that Paxlovid can inhibit over 90% of viral replication. However, its effectiveness critically depends on the timing of treatment. If treatment is initiated three days after symptoms first appear, we estimate a 17% chance of a post-treatment viral rebound and a 12% (95% CI: 0-16%) reduction in overall infectiousness for non-rebound cases. Earlier treatment significantly elevates the risk of rebound without further reducing infectiousness, whereas starting beyond five days reduces its efficacy in curbing peak viral shedding. Among the 104 patients who received Paxlovid, 62% began treatment within an optimal three-to-five-day day window after symptoms appeared. Our findings indicate that broader global access to Paxlovid, coupled with appropriately timed treatment, can mitigate the severity and transmission of SARS-Cov-2.

Comparison of clinical efficacy and safety of baloxavir marboxil versus oseltamivir as the treatment for influenza virus infections: A systematic review and meta-analysis

INTRODUCTION

Baloxavir marboxil (BXM), a newly developed cap-dependent endonuclease inhibitor, is widely used to treat influenza virus infections in inpatients and outpatients. A previous meta-analysis included only outpatients and patients suspected of having an influenza virus infection based on clinical symptoms. However, whether BXM or oseltamivir is safer and more effective for inpatients remains controversial. Therefore, we conducted a systematic review and meta-analysis validating the effectiveness and safety of BXM versus oseltamivir in inpatients with influenza virus.

METHODS

The Scopus, EMBASE, PubMed, Ichushi, and CINAHL databases were systematically searched for articles published until January 2023. The outcomes were mortality, hospitalization period, incidence of BXM- or oseltamivir-related adverse events, illness duration, and changes of virus titers and viral RNA load in patients with influenza virus infections.

RESULTS

Two randomized controlled trials with 1624 outpatients and two retrospective studies with 874 inpatients were enrolled. No deaths occurred in outpatients treated with BXM or oseltamivir. Among inpatients, BXM reduced mortality (p = 0.06) and significantly shortened hospitalization period (p = 0.01) compared to oseltamivir. In outpatients, BXM had a significantly lower incidence of adverse events (p = 0.03), reductions in influenza virus titers (p < 0.001) and viral RNA loads (p < 0.001), and a tendency to be a shorter illness duration compared with that of oseltamivir (p = 0.27).

CONCLUSIONS

Our meta-analysis showed that BXM was safer and more effective in patients than oseltamivir; thus, supporting the use of BXM for the initial treatment of patients with proven influenza virus infection.

Public Health Impact of Paxlovid as Treatment for COVID-19, United States

We evaluated the population-level benefits of expanding treatment with the antiviral drug Paxlovid (nirmatrelvir/ritonavir) in the United States for SARS-CoV-2 Omicron variant infections. Using a multiscale mathematical model, we found that treating 20% of symptomatic case-patients with Paxlovid over a period of 300 days beginning in January 2022 resulted in life and cost savings. In a low-transmission scenario (effective reproduction number of 1.2), this approach could avert 0.28 million (95% CI 0.03-0.59 million) hospitalizations and save US $56.95 billion (95% CI US $2.62-$122.63 billion). In a higher transmission scenario (effective reproduction number of 3), the benefits increase, potentially preventing 0.85 million (95% CI 0.36-1.38 million) hospitalizations and saving US $170.17 billion (95% CI US $60.49-$286.14 billion). Our findings suggest that timely and widespread use of Paxlovid could be an effective and economical approach to mitigate the effects of COVID-19.

Co-evolution of immunity and seasonal influenza viruses

Seasonal influenza viruses cause recurring global epidemics by continually evolving to escape host immunity. The viral constraints and host immune responses that limit and drive the evolution of these viruses are increasingly well understood. However, it remains unclear how most of these advances improve the capacity to reduce the impact of seasonal influenza viruses on human health. In this Review, we synthesize recent progress made in understanding the interplay between the evolution of immunity induced by previous infections or vaccination and the evolution of seasonal influenza viruses driven by the heterogeneous accumulation of antibody-mediated immunity in humans. We discuss the functional constraints that limit the evolution of the viruses, the within-host evolutionary processes that drive the emergence of new virus variants, as well as current and prospective options for influenza virus control, including the viral and immunological barriers that must be overcome to improve the effectiveness of vaccines and antiviral drugs.

Mathematical methods for scaling from within-host to population-scale in infectious disease systems

Mathematical modellers model infectious disease dynamics at different scales. Within-host models represent the spread of pathogens inside an individual, whilst between-host models track transmission between individuals. However, pathogen dynamics at one scale affect those at another. This has led to the development of multiscale models that connect within-host and between-host dynamics. In this article, we systematically review the literature on multiscale infectious disease modelling according to PRISMA guidelines, dividing previously published models into five categories governing their methodological approaches (Garira (2017)), explaining their benefits and limitations. We provide a primer on developing multiscale models of infectious diseases.

The public health impact of Paxlovid COVID-19 treatment in the United States

The antiviral drug Paxlovid has been shown to rapidly reduce viral load. Coupled with vaccination, timely administration of safe and effective antivirals could provide a path towards managing COVID-19 without restrictive non-pharmaceutical measures. Here, we estimate the population-level impacts of expanding treatment with Paxlovid in the US using a multi-scale mathematical model of SARS-CoV-2 transmission that incorporates the within-host viral load dynamics of the Omicron variant. We find that, under a low transmission scenario R e ∼ 1.2 treating 20% of symptomatic cases would be life and cost saving, leading to an estimated 0.26 (95% CrI: 0.03, 0.59) million hospitalizations averted, 30.61 (95% CrI: 1.69, 71.15) thousand deaths averted, and US$52.16 (95% CrI: 2.62, 122.63) billion reduction in health- and treatment-related costs. Rapid and broad use of the antiviral Paxlovid could substantially reduce COVID-19 morbidity and mortality, while averting socioeconomic hardship.

Editorial: Infectious Disease Epidemiology and Transmission Dynamics

Infectious diseases, such as COVID-19 [...].

Vitamin derivatives as potential drugs for Influenza Hemagglutinin

The objective of the study was to identify potential inhibitors of Influenza surface Hemagglutinin (HA), which plays key role in the entry and replication of Influenza virus into the host cell. As ligands, seven vitamins and their derivatives were selected after initial screening based on their metabolizable capacity with no reported side effects, for in silico studies. Docking, and Post docking analysis (X Score and Ligplot+) were performed against nine Influenza HA targets for the vitamins and its derivatives. 'Vitamin Derivatives' with top docking score were further analysed by MD Simulations and free energy was calculated using MMGBSA module. FMNNa and FMNCa displayed high binding free energy with Influenza HA, thereby exhibiting potential as HA inhibitors.Communicated by Ramaswamy H. Sarma.

Novel modelling approaches to predict the role of antivirals in reducing influenza transmission

To aid understanding of the effect of antiviral treatment on population-level influenza transmission, we used a novel pharmacokinetic-viral kinetic transmission model to test the correlation between nasal viral load and infectiousness, and to evaluate the impact that timing of treatment with the antivirals oseltamivir or baloxavir has on influenza transmission. The model was run under three candidate profiles whereby infectiousness was assumed to be proportional to viral titer on a natural-scale, log-scale, or dose-response model. Viral kinetic profiles in the presence and absence of antiviral treatment were compared for each individual (N = 1000 simulated individuals); subsequently, viral transmission mitigation was calculated. The predicted transmission mitigation was greater with earlier administration of antiviral treatment, and with baloxavir versus oseltamivir. When treatment was initiated 12-24 hours post symptom onset, the predicted transmission mitigation was 39.9-56.4% for baloxavir and 26.6-38.3% for oseltamivir depending on the infectiousness profile. When treatment was initiated 36-48 hours post symptom onset, the predicted transmission mitigation decreased to 0.8-28.3% for baloxavir and 0.8-19.9% for oseltamivir. Model estimates were compared with clinical data from the BLOCKSTONE post-exposure prophylaxis study, which indicated the log-scale model for infectiousness best fit the observed data and that baloxavir affords greater reductions in secondary case rates compared with neuraminidase inhibitors. These findings suggest a role for baloxavir and oseltamivir in reducing influenza transmission when treatment is initiated within 48 hours of symptom onset in the index patient.

Predictors of Seeking Care for Influenza-Like Illness in a Novel Digital Study

Background

Previous research has estimated that >50% of individuals experiencing influenza-like illness (ILI) do not seek health care. Understanding factors influencing care-seeking behavior for viral respiratory infections may help inform policies to improve access to care and protect public health. We used person-generated health data (PGHD) to identify factors associated with seeking care for ILI.

Methods

Two observational studies (FluStudy2020, ISP) were conducted during the United States 2019-2020 influenza season. Participants self-reported ILI symptoms using the online Evidation platform. A log-binomial regression model was used to identify factors associated with seeking care.

Results

Of 1667 participants in FluStudy2020 and 47 480 participants in ISP eligible for analysis, 518 (31.1%) and 11 426 (24.1%), respectively, sought health care. Participants were mostly female (92.2% FluStudy2020, 80.6% ISP) and aged 18-49 years (89.6% FluStudy2020, 89.8% ISP). In FluStudy2020, factors associated with seeking care included having health insurance (risk ratio [RR], 2.14; 95% CI, 1.30-3.54), more severe respiratory symptoms (RR, 1.53; 95% CI, 1.37-1.71), and comorbidities (RR, 1.37; 95% CI, 1.20-1.58). In ISP, the strongest predictor of seeking care was high symptom number (RR for 6/7 symptoms, 2.14; 95% CI, 1.93-2.38).

Conclusions

Using PGHD, we confirmed low rates of health care-seeking behavior for ILI and show that having health insurance, comorbidities, and a high symptom burden were associated with seeking health care. Reducing barriers in access to care for viral respiratory infections may lead to better disease management and contribute to protecting public health.

The Structural Identifiability of a Humidity-Driven Epidemiological Model of Influenza Transmission

Influenza epidemics cause considerable morbidity and mortality every year worldwide. Climate-driven epidemiological models are mainstream tools to understand seasonal transmission dynamics and predict future trends of influenza activity, especially in temperate regions. Testing the structural identifiability of these models is a fundamental prerequisite for the model to be applied in practice, by assessing whether the unknown model parameters can be uniquely determined from epidemic data. In this study, we applied a scaling method to analyse the structural identifiability of four types of commonly used humidity-driven epidemiological models. Specifically, we investigated whether the key epidemiological parameters (i.e., infectious period, the average duration of immunity, the average latency period, and the maximum and minimum daily basic reproductive number) can be uniquely determined simultaneously when prevalence data is observable. We found that each model is identifiable when the prevalence of infection is observable. The structural identifiability of these models will lay the foundation for testing practical identifiability in the future using synthetic prevalence data when considering observation noise. In practice, epidemiological models should be examined with caution before using them to estimate model parameters from epidemic data.

Effects of baloxavir and oseltamivir antiviral therapy on the transmission of seasonal influenza in China: A mathematical modeling analysis

New antiviral influenza treatments can effectively alleviate illness while reducing viral shedding. However, how such effects can translate into lower population infections of seasonal influenza in China remains unknown. To shed light on the public health impacts of novel antiviral agents for influenza, we constructed a dynamic transmission model to simulate the seasonal influenza epidemics in China. Two antivirus treatments, baloxavir and oseltamivir, were evaluated by estimating their impacts on the incidences of influenza infection in a single flu season. In the base-case analysis of a 10% antiviral treatment uptake rate, 2760 and 3420 per 10 000 persons contracted influenza under the treatment of baloxavir and oseltamivir, respectively. These incidence rates amounted to an 18.90% relative risk reduction (RRR) of infection associated with baloxavir in relation to oseltamivir. The corresponding RRR was 82.16% when the antiviral treatment uptake rate was increased to 35%. In addition, the peak of the prevalence of infected individuals per 10 000 persons under the baloxavir treatment was 177 (range: 93-274) fewer than that of oseltamivir. Our analyses suggest that the baloxavir treatment strategy reduces the incidence of influenza in China compared with oseltamivir in the setting of a seasonal flu epidemic. Also, increasing the uptake rate of antiviral treatment can potentially prevent millions of infections during a single flu season.

In Silico Drug Repurposing of FDA-Approved Drugs Highlighting Promacta as a Potential Inhibitor of H7N9 Influenza Virus

Influenza virus infections continue to be a significant and recurrent public health problem. Although vaccine efficacy varies, regular immunisation is the most effective method for suppressing the influenza virus. Antiviral drugs are available for influenza, although two of the four FDA-approved antiviral treatments have resulted in significant drug resistance. Therefore, new treatments are being sought to reduce the burden of flu-related illness. The time-consuming development of treatments for new and re-emerging diseases such as influenza and the high failure rate are increasing concerns. In this context, we used an in silico-based drug repurposing method to repurpose FDA-approved drugs as potential therapies against the H7N9 virus. To find potential inhibitors, a total of 2568 drugs were screened. Promacta, tucatinib, and lurasidone were identified as promising hits in the DrugBank database. According to the calculations of MM-GBSA, tucatinib (−54.11 kcal/mol) and Promacta (−56.20 kcal/mol) occupied the active site of neuraminidase with a higher binding affinity than the standard drug peramivir (−49.09 kcal/mol). Molecular dynamics (MD) simulation studies showed that the C-α atom backbones of the complexes of tucatinib and Promacta neuraminidase were stable throughout the simulation period. According to ADME analysis, the hit compounds have a high gastrointestinal absorption (GI) and do not exhibit properties that allow them to cross the blood–brain barrier (BBB). According to the in silico toxicity prediction, Promacta is not cardiotoxic, while lurasidone and tucatinib show only weak inhibition. Therefore, we propose to test these compounds experimentally against the influenza H7N9 virus. The investigation and validation of these potential H7N9 inhibitors would be beneficial in order to bring these compounds into clinical settings.

Wearable sensor-based detection of influenza in presymptomatic and asymptomatic individuals

BACKGROUND

The COVID-19 pandemic highlighted the need for early detection of viral infections in symptomatic and asymptomatic individuals to allow for timely clinical management and public health interventions.

METHODS

Twenty healthy adults were challenged with an influenza A (H3N2) virus and prospectively monitored from 7 days before through 10 days after inoculation, using wearable electrocardiogram and physical activity sensors (Clinical Trial: NCT04204493; https://clinicaltrials.gov/ct2/show/NCT04204993). This framework allowed for responses to be accurately referenced to the infection event. For each participant, we trained a semi-supervised multivariable anomaly detection model on data acquired before inoculation and used it to classify the post-inoculation dataset.

RESULTS

Inoculation with this challenge virus was well-tolerated with an infection rate of 85%. With the model classification threshold set so that no alarms were recorded in the 170 healthy days recorded, the algorithm correctly identified 16 of 17 (94%) positive presymptomatic and asymptomatic individuals, on average 58 hours post inoculation and 23 hrs before the symptom onset.

CONCLUSION

The data processing and modeling methodology show promise for the early detection of respiratory illness. The detection algorithm is compatible with data collected from smartwatches using optical techniques but needs to be validated in large heterogeneous cohorts in normal living conditions.

A Tale of Three Recent Pandemics: Influenza, HIV and SARS-CoV-2

Emerging infectious diseases are one of the main threats to public health, with the potential to cause a pandemic when the infectious agent manages to spread globally. The first major pandemic to appear in the 20th century was the influenza pandemic of 1918, caused by the influenza A H1N1 strain that is characterized by a high fatality rate. Another major pandemic was caused by the human immunodeficiency virus (HIV), that started early in the 20th century and remained undetected until 1981. The ongoing HIV pandemic demonstrated a high mortality and morbidity rate, with discrepant impacts in different regions around the globe. The most recent major pandemic event, is the ongoing pandemic of COVID-19, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has caused over 5.7 million deaths since its emergence, 2 years ago. The aim of this work is to highlight the main determinants of the emergence, epidemic response and available countermeasures of these three pandemics, as we argue that such knowledge is paramount to prepare for the next pandemic. We analyse these pandemics’ historical and epidemiological contexts and the determinants of their emergence. Furthermore, we compare pharmaceutical and non-pharmaceutical interventions that have been used to slow down these three pandemics and zoom in on the technological advances that were made in the progress. Finally, we discuss the evolution of epidemiological modelling, that has become an essential tool to support public health policy making and discuss it in the context of these three pandemics. While these pandemics are caused by distinct viruses, that ignited in different time periods and in different regions of the globe, our work shows that many of the determinants of their emergence and countermeasures used to halt transmission were common. Therefore, it is important to further improve and optimize such approaches and adapt it to future threatening emerging infectious diseases.

Discovery of oseltamivir-based novel PROTACs as degraders targeting neuraminidase to combat H1N1 influenza virus

Annual and sporadic influenza outbreaks pose a great threat to human health and the economy worldwide. Moreover, the frequent mutation of influenza viruses caused by antigen drift complicates the application of antiviral therapeutics. As such, there is an urgent need for novel antiviral agents to tackle the problem of insufficient efficacy of licensed drugs. Inspired by the success of the newly emerged PROTACs (PROteolysis TArgeting Chimeras) strategy, we report herein the design and synthesis of novel PROTAC molecules based on an oseltamivir scaffold to combat severe annual influenza outbreaks. Among these, several compounds showed good anti-H1N1 activity and efficient influenza neuraminidase (NA) degradation activity. The best compound, 8e, effectively induced influenza NA degradation in a dose-dependent manner and relied on the ubiquitin-proteasome pathway. Moreover, Compound 8e exhibited potent antiviral activity toward both wild-type H1N1 virus and an oseltamivir-resistant strain (H1N1, H274Y). A molecular docking study demonstrated that Compound 8e had good hydrogen-bonding and hydrophobic interactions with both the active sites of NA and Von Hippel-Lindau (VHL) proteins, which could effectively drive the favorable interaction of these two proteins. Thus, as the first report of a successful anti-influenza PROTAC, this proof of concept will greatly widen the application range of the PROTAC technique to antiviral drug discovery.

Antiviral Efficacy of Molnupiravir for COVID-19 Treatment

The ongoing global pandemic of COVID-19 poses unprecedented public health risks for governments and societies around the world, which have been exacerbated by the emergence of SARS-CoV-2 variants. Pharmaceutical interventions with high antiviral efficacy are expected to delay and contain the COVID-19 pandemic. Molnupiravir, as an oral antiviral prodrug, is active against SARS-CoV-2 and is now (23 February 2022) one of the seven widely-used coronavirus treatments. To estimate its antiviral efficacy of Molnupiravir, we built a granular mathematical within-host model. We find that the antiviral efficacy of Molnupiravir to stop the growth of the virus is 0.56 (95% CI: 0.49, 0.64), which could inhibit 56% of the replication of infected cells per day. There has been good progress in developing high-efficacy antiviral drugs that rapidly reduce viral load and may also reduce the infectiousness of treated cases if administered as early as possible.

Discovery of Aryl Benzoyl Hydrazide Derivatives as Novel Potent Broad-Spectrum Inhibitors of Influenza A Virus RNA-Dependent RNA Polymerase (RdRp)

Influenza A viruses possess a high antigenic shift, and the approved anti-influenza drugs are extremely limited, which makes the development of novel anti-influenza drugs for the clinical treatment and prevention of influenza outbreaks imperative. Herein, we report a series of novel aryl benzoyl hydrazide analogs as potent anti-influenza agents. Particularly, analogs 10b, 10c, 10g, 11p, and 11q exhibited potent inhibitory activity against the avian H5N1 flu strain with EC₅₀ values ranging from 0.009 to 0.034 μM. Moreover, compound 11q exhibited nanomolar antiviral effects against both the H1N1 virus and Flu B virus and possessed good oral bioavailability and inhibitory activity against influenza A virus in a mouse model. Preliminary mechanistic studies suggested that these compounds exert anti-influenza virus effects mainly by interacting with the PB1 subunit of RNA-dependent RNA polymerase (RdRp). These results revealed that 11q has the potential to become a potent clinical candidate to combat seasonal influenza and influenza pandemics.

Comparison of intra-familial transmission of influenza virus from index patients treated with baloxavir marboxil or oseltamivir using an influenza transmission model and a health insurance claims database

Background

Influenza affects approximately a billion people globally, including > 10 million Japanese individuals every year. Baloxavir marboxil (baloxavir [BXM]; a selective cap-dependent endonuclease inhibitor) is approved for influenza treatment in Japan. We compared the incidence of intra-familial transmission of influenza between BXM and oseltamivir (OTV) treatments using a simulation model.

Methods

Using the JMDC Claims Database, we identified index case (IC) as the first family member diagnosed with influenza during the 2018–19 influenza season, and classified the families into BXM or OTV group per the drug dispensed to ICs. Using a novel influenza intra-familial infection model, we simulated the duration of influenza infection in ICs based on agent-specific virus shedding periods. Intra-familial infections were defined as non-IC family members infected during the agent-specific viral shedding period in ICs. The virus incubation periods in the non-IC family members were considered to exclude secondary infections from potentially external exposure. The primary endpoint was proportion of families with intra-familial infections. For between-group comparisons, we used a multivariate logistic regression model.

Results

The median proportion of families with intra-familial transmission was 9.57% and 19.35% in the BXM (N = 84 672) and OTV (N = 62 004) groups, respectively. The multivariate odds ratio of 1.73 (2.5th–97.5th percentiles, 1.68–1.77) indicated a substantially higher incidence of intra-familial infections in the OTV group versus the BXM group. Subgroup analyses by ICs’ age category, virus type, and month of onset revealed similar trends favoring BXM.

Conclusions

BXM treatment of ICs may contribute to a greater reduction in intra-familial influenza transmission than OTV treatment.

Mitigating COVID-19 Transmission in Schools With Digital Contact Tracing

Precision mitigation of COVID-19 is in pressing need for postpandemic time with the absence of pharmaceutical interventions. In this study, the effectiveness and cost of digital contact tracing (DCT) technology-based on-campus mitigation strategy are studied through epidemic simulations using high-resolution empirical contact networks of teachers and students. Compared with traditional class, grade, and school closure strategies, the DCT-based strategy offers a practical yet much more efficient way of mitigating COVID-19 spreading in the crowded campus. Specifically, the strategy based on DCT can achieve the same level of disease control as rigid school suspensions but with significantly fewer students quarantined. We further explore the necessary conditions to ensure the effectiveness of DCT-based strategy and auxiliary strategies to enhance mitigation effectiveness and make the following recommendation: social distancing should be implemented along with DCT, the adoption rate of DCT devices should be assured, and swift virus tests should be carried out to discover asymptomatic infections and stop their subsequent transmissions. We also argue that primary schools have higher disease transmission risks than high schools and, thereby, should be alerted when considering reopenings.

Influenza Management During the COVID-19 Pandemic: A Review of Recent Innovations in Antiviral Therapy and Relevance to Primary Care Practice

Seasonal influenza requires appropriate management to protect public health and resources. Decreasing the burden of influenza will depend primarily on increasing vaccination rates as well as prompt initiation of antiviral therapy within 48 hours of symptom onset, especially in the context of the current coronavirus disease 2019 pandemic. A careful approach is required to prevent health services from being overwhelmed by a surge in demand that could exceed capacity. This review highlights the societal burden of influenza and discusses the prevention, diagnosis, and treatment of influenza as a complicating addition to the challenges of the coronavirus disease 2019 pandemic. The importance of vaccination for seasonal influenza and the role of antiviral therapy in the treatment and prophylaxis of seasonal influenza, including the most up-to-date recommendations from the Centers for Disease Control and Prevention for influenza management, will also be reviewed.

Influenza polymerase inhibitor resistance: Assessment of the current state of the art - A report of the isirv Antiviral group

It is more than 20 years since the neuraminidase inhibitors, oseltamivir and zanamivir were approved for the treatment and prevention of influenza. Guidelines for global surveillance and methods for evaluating resistance were established initially by the Neuraminidase Inhibitor Susceptibility Network (NISN), which merged 10 years ago with the International Society for influenza and other Respiratory Virus Diseases (isirv) to become the isirv-Antiviral Group (isirv-AVG). With the ongoing development of new influenza polymerase inhibitors and recent approval of baloxavir marboxil, the isirv-AVG held a closed meeting in August 2019 to discuss the impact of resistance to these inhibitors. Following this meeting and review of the current literature, this article is intended to summarize current knowledge regarding the clinical impact of resistance to polymerase inhibitors and approaches for surveillance and methods for laboratory evaluation of resistance, both in vitro and in animal models. We highlight limitations and gaps in current knowledge and suggest some strategies for addressing these gaps, including the need for additional clinical studies of influenza antiviral drug combinations. Lessons learned from influenza resistance monitoring may also be helpful for establishing future drug susceptibility surveillance and testing for SARS-CoV-2.

Personalized Virus Load Curves for Acute Viral Infections

We introduce an explicit function that describes virus-load curves on a patient-specific level. This function is based on simple and intuitive model parameters. It allows virus load analysis of acute viral infections without solving a full virus load dynamic model. We validate our model on data from mice influenza A, human rhinovirus data, human influenza A data, and monkey and human SARS-CoV-2 data. We find wide distributions for the model parameters, reflecting large variability in the disease outcomes between individuals. Further, we compare the virus load function to an established target model of virus dynamics, and we provide a new way to estimate the exponential growth rates of the corresponding infection phases. The virus load function, the target model, and the exponential approximations show excellent fits for the data considered. Our virus-load function offers a new way to analyze patient-specific virus load data, and it can be used as input for higher level models for the physiological effects of a virus infection, for models of tissue damage, and to estimate patient risks.

Reusable surface amplified nanobiosensor for the sub PFU/mL level detection of airborne virus

We developed a reusable surface-amplified nanobiosensor for monitoring airborne viruses with a sub-PFU/mL level detection limit. Here, sandwich structures consisted of magnetic particles functionalized with antibodies, target viruses, and alkaline phosphatases (ALPs) were formed, and they were magnetically concentrated on Ni patterns near an electrochemical sensor transducer. Then, the electrical signals from electrochemical markers generated by ALPs were measured with the sensor transducer, enabling highly-sensitive virus detection. The sandwich structures in the used sensor chip could be removed by applying an external magnetic field, and we could reuse the sensor transducer chip. As a proof of concepts, the repeated detection of airborne influenza virus using a single sensor chip was demonstrated with a detection limit down to a sub-PFU/mL level. Using a single reusable sensor transducer chip, the hemagglutinin (HA) of influenza A (H1N1) virus with different concentrations were measured down to 10 aM level. Importantly, our sensor chip exhibited reliable sensing signals even after more than 18 times of the repeated HA sensing measurements. Furthermore, airborne influenza viruses collected from the air could be measured down to 0.01 PFU/mL level. Interestingly, the detailed quantitative analysis of the measurement results revealed the degradation of HA proteins on the viruses after the air exposure. Considering the ultrasensitivity and reusability of our sensors, it can provide a powerful tool to help preventing epidemics by airborne pathogens in the future.

Substitution of I222L-E119V in neuraminidase from highly pathogenic avian influenza H7N9 virus exhibited synergistic resistance effect to oseltamivir in mice

That the high frequency and good replication capacity of strains with reduced susceptibility to neuraminidase inhibitors (NAIs) in highly pathogenic avian influenza H7N9 (HPAI H7N9) virus made it a significance to further study its drug resistance. HPAI H7N9 viruses bearing NA I222L or E119V substitution and two mutations of I222L-E119V as well as their NAIs-sensitive counterpart were generated by reverse genetics for NA inhibition test and replication capability evaluation in vitro. The attenuated H7N9/PR8 recombinant viruses were developed to study the pathogenicity and drug resistance brought by the above substitutions to mice. The IC₅₀ fold change of oseltamivir to HPAI H7N9 with NA222L-119V is 306.34 times than that of its susceptible strain, and 3.5 times than the E119V mutant virus. HPAI H7N9 bearing NA222L-119V had good replication ability with peak value of more than 6log₁₀ TCID₅₀/ml in MDCK cells. H7N9/PR8 virus bearing NA222L-119V substitutions leaded to diffuse pneumonia, significant weight loss and fatality in mice. NA E119V made H7N9/PR8 virus resistant to oseltamivir, and I222L-E119V had synergistic resistance to oseltamivir in mice. Due to the good fitness of drug resistant strains of HPAI H7N9 virus, it is necessary to strengthen drug resistance surveillance and new drug research.

Reducing influenza virus transmission: the value of antiviral treatment

Prompt antiviral treatment has the potential to reduce influenza virus transmission to close contacts, but rigorous data on the magnitude of treatment effects on transmission are limited. Animal model data indicate that rapid reductions in viral replication after antiviral treatment reduce the risk of transmission. Observational and clinical trial data with oseltamivir and other neuraminidase inhibitors indicate that prompt treatment of household index patients seems to reduce the risk of illness in contacts, although the magnitude of the reported effects has varied widely across studies. In addition, the potential risk of transmitting drug-resistant variants exists with all approved classes of influenza antivirals. A controlled trial examining baloxavir treatment efficacy to reduce transmission, including the risk of transmitting virus with reduced baloxavir susceptibility, is currently in progress. If reduced transmission risk is confirmed, modeling studies indicate that early treatment could have major epidemiologic benefits in seasonal and pandemic influenza.

Blueprint for pandemic response: Focus on translational medicine, clinical pharmacology and pharmacometrics

Perhaps the most important lesson learned from the COVID-19 pandemic is that of preparedness. Enhanced surveillance systems for early threat detection will be crucial to maximizing response time for implementation of public health measures and mobilization of resources in containing an emerging pandemic. Recent outbreaks have been dominated by viral pathogens, with RNA respiratory viruses being the most likely to have pandemic potential. These should therefore be a preparedness priority. Tools in the areas of virology, drug discovery, clinical pharmacology, translational medicine and pharmacometrics should be considered key components in the rapid identification and development of existing and novel interventions for a pandemic response. Prioritization of therapeutics should be based on in vitro activity, likelihood of achieving effective drug concentrations at the site of action, and safety profile at the doses that will be required for clinical efficacy. Deployment strategies must be tailored to the epidemiology of the disease, and the adequacy of the response should be re-evaluated in view of evolving epidemiological factors. An interdisciplinary framework integrating drug pharmacology, viral kinetics, epidemiology and health economics could help optimize the deployment strategy by improving decision-making around who to treat, when to treat, and with what type of intervention for optimal outcomes. Lastly, while an effective vaccine will ultimately end a pandemic, antiviral drug intervention guided by clinical pharmacology principles will continue to play a critical role in any pandemic response.

Baloxavir Marboxil: A Review in Acute Uncomplicated Influenza

Baloxavir marboxil (Xofluza^®; hereafter referred to as baloxavir), the prodrug of baloxavir acid, is a first-in-class, small molecule inhibitor of the polymerase acidic (PA) protein subunit of the influenza virus polymerase complex. Baloxavir (after conversion to baloxavir acid) acts to block influenza virus replication by inhibiting the cap-dependent endonuclease activity of the PA protein. Taken orally as a single dose, baloxavir is approved in the USA for the treatment of acute uncomplicated influenza in patients ≥ 12 years of age who have been symptomatic for ≤ 48 h. Data from randomized, double-blind, placebo- and oseltamivir-controlled phase III trials have shown that baloxavir is efficacious in improving influenza symptoms both in otherwise healthy adolescents and adults and in those at high risk of influenza complications, displaying similar efficacy to that of oseltamivir. Furthermore, there is evidence that baloxavir can reduce influenza viral load more rapidly than oseltamivir. Baloxavir has activity against influenza A and B viruses (including strains resistant to neuraminidase inhibitors) and is well tolerated. Evidence of the emergence and likely human-to-human transmission of variant viruses with reduced susceptibility to baloxavir highlights the importance of monitoring and surveillance for changes in influenza virus drug susceptibility patterns. However, currently available evidence suggests that baloxavir, with the benefits of a single oral dose regimen, provides a useful alternative to neuraminidase inhibitors for the treatment of acute uncomplicated influenza in adolescents and adults.

Neuraminidase inhibitors and single dose baloxavir are effective and safe in uncomplicated influenza: a meta-analysis of randomized controlled trials

BACKGROUND

Scarce evidence verifying the clinical impact of baloxavir on influenza complications is found.

METHODS

PubMed, Cochrane Library, and Web of Science databases were searched through December 2020. Randomized-controlled trials (RCT) that enrolled patients with laboratory-confirmed influenza receiving neuraminidase inhibitors (NAI) or baloxavir comparing to placebo were assessed. PROSPERO Registration-number: CRD42021226854.

RESULTS

Twenty-one RCTs (11,697 patients) were included. Antiviral administration significantly reduced time to clinical resolution (mean difference: -21.3 hours) and total influenza-related complications (OR:0.55, 95%CI: 0.42-0.73). Specifically, antivirals significantly decreased bronchitis (OR:0.54, 95%CI: 0.38-0.75), sinusitis (OR:0.51, 95%CI: 0.33-0.78), acute otitis media (OR:0.48, 95%CI: 0.30-0.77), and antibiotic prescription (OR:0.62; 95%CI: 0.48-0.80). A positive trend favored antivirals administration to reduce pneumonia (OR:0.47, 95%CI: 0.16-1.33), or hospitalization rates (OR:0.65; 95%CI: 0.34-1.24) compared to placebo, but did not reach statistical significance. Adverse events (AE) were reported in 11%, 8.9%, and 5.1% of NAIs, placebo and baloxavir recipients, respectively. Compared with NAIs, administration of baloxavir showed non-significantly reduced AEs (OR:0.74, 95%CI: 0.53-1.04).

CONCLUSIONS

Single-dose baloxavir and NAIs were superior to placebo to reduce complications in uncomplicated influenza, with 40% significant reduction in antibiotic prescription. Safety and efficacy of single-dose baloxavir were non-inferior to NAIs.

Estimation of the value of convenience in taking influenza antivirals in Japanese adult patients between baloxavir marboxil and neuraminidase inhibitors using a conjoint analysis

AIMS

Estimating the monetary value of the convenience of using influenza antivirals approved in Japan from a patient perspective using a conjoint analysis.

METHODS

An online survey (August 2020) was performed on individuals aged 20-64 years living in Japan who had taken oral or inhalant antivirals for influenza treatment in the 2018/19 or 2019/20 seasons. Efficacy and safety were assumed to be equivalent among the antivirals. The attributes for the conjoint analysis included route (oral or inhalant), duration, frequency of administration, and out-of-pocket expenses. A conditional logit model was applied as a baseline model. The monetary value of each attribute was calculated by comparing the same utility of the linearly interpolated level of the out-of-pocket attribute. Another survey to determine the experiences of the latest antiviral intake was also conducted on the same respondents.

RESULTS

Of the respondents, 1,550 were men and 1,587 were women. The monetary value for oral antivirals was estimated to be higher, saving JPY 741 (USD 7.06, as of August 2020), compared with inhalant. Regarding the length and frequency of administration, five days corresponds to an increase of JPY 2,072, compared with one day, and twice a day corresponds to a JPY 574 increase compared to once a day.

CONCLUSIONS

The results suggest that - among the antivirals approved in Japan - the monetary value of the utility is the highest in the single dose oral antiviral, baloxavir marboxil (baloxavir). Although the drug cost was highest in baloxavir among the brand antivirals, the difference in the value of utility for influenza patient was estimated to be larger than the difference in the drug costs.

LIMITATIONS

Although individuals with diverse attributes from all over the country were included in the survey, they are not necessarily a representative population of the Japanese society.

Reflecting on prediction strategies for epidemics: Preparedness and public health response

Objective

To provide an overview of the literature on respiratory infectious disease epidemic prediction, preparedness, and response (including pharmaceutical and nonpharmaceutical interventions) and their impact on public health, with a focus on respiratory conditions such as asthma.

Data Sources

Published literature obtained through PubMed database searches.

Study Selections

Studies relevant to infectious epidemics, asthma, modeling approaches, health care access, and data analytics related to intervention strategies.

Results

Prediction, prevention, and response strategies for infectious disease epidemics use extensive data sources and analytics, addressing many areas including testing and early diagnosis, identifying populations at risk of severe outcomes such as hospitalizations or deaths, monitoring and understanding transmission and spread patterns by age group, social interactions geographically and over time, evaluating the effectiveness of pharmaceutical and nonpharmaceutical interventions, and understanding prioritization of and access to treatment or preventive measures (eg, vaccination, masks), given limited resources and system constraints.

Conclusion

Previous epidemics and pandemics have revealed the importance of effective preparedness and response. Further research and implementation need to be performed to emphasize timely and actionable strategies, including for populations with particular health conditions (eg, chronic respiratory diseases) at risk for severe outcomes.