Oseltamivir for treatment and prevention of pandemic influenza A/H1N1 virus infection in households, Milwaukee, 2009

Abstract

BackgroundDuring an influenza pandemic, a substantial proportion of transmission is thought to occur in households. We used data on influenza progression in individuals and their contacts collected by the City of Milwaukee Health Department (MHD) to study the transmission of pandemic influenza A/H1N1 virus in 362 households in Milwaukee, WI, and the effects of oseltamivir treatment and chemoprophylaxis.Methods135 households had chronological information on symptoms and oseltamivir usage for all household members. The effect of oseltamivir treatment and other factors on the household secondary attack rate was estimated using univariate and multivariate logistic regression with households as the unit of analysis. The effect of oseltamivir treatment and other factors on the individual secondary attack rate was estimated using univariate and multivariate logistic regression with individual household contacts as the unit of analysis, and a generalized estimating equations approach was used to fit the model to allow for clustering within households.ResultsOseltamivir index treatment on onset day or the following day (early treatment) was associated with a 42% reduction (OR: 0.58, 95% CI: 0.19, 1.73) in the odds of one or more secondary infections in a household and a 50% reduction (OR: 0.5, 95% CI: 0.17, 1.46) in the odds of a secondary infection in individual contacts. The confidence bounds are wide due to a small sample of households with early oseltamivir index usage - in 29 such households, 5 had a secondary attack. Younger household contacts were at higher risk of infection (OR: 2.79, 95% CI: 1.50-5.20).ConclusionsEarly oseltamivir treatment may be beneficial in preventing H1N1pdm influenza transmission; this may have relevance to future control measures for influenza pandemics. Larger randomized trials are needed to confirm this finding statistically.

Household Transmission of 2009 Pandemic Influenza A (H1N1)

“…Three studies reported that both SIR PCR and SIR FARI were higher among household contacts of younger index cases, 22,25,33 two studies reported that they were lower with younger index cases, 19,29 and one study found no difference by index age. 41 Four studies that stratified by sex found no difference in SIRs, 27,34,40,41 while one study reported female contacts to be at greater risk of infection 24 and another that adult women were more likely to transmit pH1N1 to children.…”

Risk Factors of Household Transmission of Pandemic (H1N1) 2009 among Patients Treated with Antivirals: A Prospective Study at a Primary Clinic in Japan

“…Family size and the number of children are recognized as risk factors for household transmission in previous studies [5], [28], [29]. However, contact between patients and healthy persons in the household could differ based on cultural and familial factors and the size of the house [24].…”

Household Transmission of Influenza (H1N1-2009) in Japan: Age-Specificity and Reduction of Household Transmission Risk by Zanamivir Treatment

“…11 Thirdly, the present study was underpowered to determine significant reductions in the risk of household transmission during antiviral prophylaxis, therefore the findings on the Oseltamivir treatment within 24 h was, however, shown to yield an odds ratio of 0.62, which was not statistically significant, but is broadly consistent with published studies. 13,15 The simple adjustment of the age-effect in the statistical model may not have been enough to correct for confounding factors. This is also a problem when an age-specific treatment strategy is employed.…”