Patterns in influenza antiviral medication use before and during the 2009 H1N1 pandemic, Vaccine Safety Datalink Project, 2000-2010

Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, MA, USA Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, USA Immunization Safety Office, Division of Healthcare Quality and Promotion, Centers for Disease Control and Prevention, Atlanta, GA, USA Kaiser Permanente Vaccine Study Center, Oakland, CA, USA Group Health Research Institute, Seattle, WA, USA Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA HealthPartners Research Foundation, Minneapolis, MN, USA Marshfield Clinic Research Foundation, Marshfield, WI, USA Kaiser Permanente Northwest Center for Health Research, Portland, OR, USA Institute for Health Research, Kaiser Permanente Colorado, Denver, CO, USA Division of General Pediatrics, Children's Hospital Boston, Boston, MA, USA.
Influenza and Other Respiratory Viruses (Impact Factor: 2.2). 06/2012; 6(6):e143-e151. DOI: 10.1111/j.1750-2659.2012.00390.x
Source: PubMed


U.S. recommendations for using influenza antiviral medications changed in response to viral resistance (to reduce adamantane use) and during the 2009 H1N1 pandemic (to focus on protecting high-risk patients). Little information is available on clinician adherence to these recommendations. We characterized population-based outpatient antiviral medication usage, including diagnosis and testing practices, before and during the pandemic.

Eight medical care organizations in the Vaccine Safety Datalink Project provided data on influenza antiviral medication dispensings from January 2000 through June 2010. Dispensing rates were explored in relation to changes in recommendations and influenza diagnosis and laboratory testing frequencies. Factors associated with oseltamivir dispensings in pandemic versus pre-pandemic periods were identified using multivariable logistic regression.

Antiviral use changed coincident with recommendations to avoid adamantanes in 2006, to use alternatives to oseltamivir in 2008, and to use oseltamivir during the pandemic. Of 38,019 oseltamivir dispensings during the pandemic, 31% were to patients not assigned an influenza diagnosis, and 97% were to patients not tested for influenza. Oseltamivir was more likely to be dispensed in pandemic versus pre-pandemic periods to patients <25 years old and to those with underlying conditions, including chronic pulmonary disease or pregnancy (P<0.0001 for each factor in multivariable analysis).

Antiviral medication usage patterns suggest that clinicians followed recommendations to change antiviral prescribing based on resistance and to focus on high-risk patients during the pandemic. Medications were commonly dispensed to patients without influenza diagnoses and tests, suggesting that antiviral dispensings may offer useful supplemental data for monitoring influenza incidence.

Download full-text


Available from: David K Shay, Nov 19, 2014
  • Source
    • "In contrast, individuals aged 65 years or older had a much lower outpatient prescription rate (0.8%) despite that they were more vulnerable to severe influenza-related complications, if they were to acquire an infection. From the ICD-9 diagnosis in outpatients department visit in Taiwan in 2009 pandemic, children and adolescents had about four-fold higher numbers of ILI visit comparison to those aged 65 years or older [7]. Children and adolescents had a six-fold higher incidence of seropositivity in comparison to those aged 65 years or older [13]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The Taiwan CDC provided free oseltamivir to all patients with influenza infections confirmed by rapid testing or who had clinical warning symptoms during the 2009 H1N1 influenza pandemic in Taiwan. However, oseltamivir utilization patterns, cost, and outcomes among oseltamivir-treated patients remained unclear. A population-level, observational cohort study was conducted using the Taiwan National Health Insurance Database from January to December 2009 to describe the use of oseltamivir.Result: Prescription trend over weeks increased after a change in government policy and responded to the influenza virus activity. The overall prescription rate was 22.33 per 1000 persons, with the highest prescription rate of 116.5 for those aged 7--12 years, followed by 69.0 for those aged 13--18 years, while the lowest rate was 1.7 for those aged >= 65 years. As influenza virus activity increased, the number of prescriptions for those aged <=18 years rose significantly, whereas no substantial change was observed for those aged >=65 years. There were also regional variations in terms of oseltamivir utilization and influenza complication rates. Oseltamivir was widely used in the 2009 H1N1 influenza pandemic in Taiwan, particularly in those aged 7--18 years. The number of prescriptions for oseltamivir increased with a change in government policy and with increasing cases of pandemic influenza. Further study is needed to examine whether there is an over- or under-use of anti-influenza drugs in different age groups or regions and to examine the current policy of public use of anti-influenza drugs to reduce influenza-associated morbidity and mortality.
    Full-text · Article · Jul 2013 · BMC Public Health
  • [Show abstract] [Hide abstract]
    ABSTRACT: An association between the influenza antiviral medication oseltamivir and neuropsychiatric events has been suggested by post-marketing case reports in Japan. This possible association was not supported by cohort studies in the U.S. conducted prior to the 2009 influenza A (H1N1) pandemic, when usage rates were comparatively low. We assessed oseltamivir safety before and during the pandemic using biologically plausible risk intervals, particularly focusing on psychiatric events. Outpatients with influenza episodes from January 2007 through June 2010 were identified using diagnosis codes and positive tests at eight health care systems (sites) in the Vaccine Safety Datalink Project. Oseltamivir-treated and untreated patients were matched according to calendar week, age, sex, site, and propensity for treatment. Within this matched cohort, conditional logistic regression models were used to estimate the risk of four neuropsychiatric and five other adverse events (AEs) during pre-specified risk intervals. Among 27 684 matched pairs, no associations were identified between oseltamivir treatment and any pre-defined AE. The absolute risks of incident psychiatric events in the 1–7 day risk interval were 0.126% for oseltamivir-treated and 0.105% for untreated patients (odds ratio = 1.21, 95% confidence interval [CI]: 0.74, 1.97; risk difference = 0.022%, 95% CI: −0.035%, 0.078%); the most common diagnosis was unspecified anxiety state. Results were similar for 1–14 and 1–2 day risk intervals and for pediatric/adolescent subgroups. Consistent with prior U.S. cohort studies, no evidence was identified for an increased risk of neuropsychiatric or other AEs following oseltamivir treatment. Safety should be prospectively monitored to inform antiviral medication usage recommendations. Copyright
    No preview · Article · Apr 2013 · Pharmacoepidemiology and Drug Safety
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The World Health Organization recommends early antiviral treatment for patients with severe influenza illness or those at increased risk for severe illness. The aim of this study was to determine the proportion of cases with laboratory-confirmed A(H1N1)pdm09 infection that have been treated with antivirals in Germany during the pandemic (H1N1) 2009 and to investigate factors associated with the use of antivirals. We analyzed cases with laboratory-confirmed A(H1N1)pdm09 infection notified to national health authorities in Germany between week 29/2009 and week 17/2010 using multivariable logistic regression. Severity of disease was defined by pneumonia or death. Of 160 804 cases with laboratory-confirmed A(H1N1)pdm09 infection, 22% were treated with antivirals. Cases with severe disease were more likely to be treated with antivirals than cases without severe disease (odds ratio = 1·66; 95% confidence interval: 1·46-1·89). In the group with at least one underlying medical condition, only children aged between 1 and 4 years had significant lower odds for receiving antiviral treatment compared with cases in the age group 15 to 49 years (odds ratio = 0·75; 95% confidence interval: 0·6-0·94). In conclusion, the implementation of international recommendations on use of antivirals differed according to the age of patients in Germany during the pandemic (H1N1) 2009. This indicates that the potential of antivirals to prevent severe influenza might not have been fully exhausted. The reasons leading to the observed differences in patient management need to be investigated.
    Preview · Article · Aug 2013 · Influenza and Other Respiratory Viruses
Show more