Should antivirals play a bigger role in reducing family transmission influenza?

A single dose of baloxavir could effectively protect against virus transmission within a family, researchers at the University of Michigan have found.They conducted a Phase IIIb clinical trial to evaluate the efficacy of a single-dose antiviral drug, baloxavir (approved by Health Canada since 2020), in reducing the transmission of influenza in the home environment and thus helping to combat epidemics and pandemics.A total of 1,457 influenza-positive index patients and 2,681 household contacts were recruited during the 2019-2024 influenza seasons. Influenza-positive index patients, aged between five and 64 years, were randomized in a 1:1 ratio to receive baloxavir or placebo within 48 hours of symptom onset—726 index patients were assigned to the baloxavir group and 731 to the placebo group.The primary endpoint was transmission of influenza virus from an index patient to a household contact before day five. The primary secondary endpoint was transmission of influenza virus before day five, leading to symptom onset.On day five, laboratory-confirmed influenza transmission 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 symptomatic influenza transmission on day five was 5.8% with baloxavir and 7.6% with placebo, but the difference was not significant (adjusted odds ratio, 0.75; 95.38% CI, 0.50 to 1.12; P = 0.16).“A difference in the incidence of transmission favouring baloxavir over placebo was observed across age groups, seasons, influenza types, time from symptom onset to receipt of baloxavir or placebo, and geographic regions,” the authors stated.Selective pressureIn addition, the emergence of drug-resistant viruses during the follow-up period occurred in 7.2% (95% CI, 4.1 to 11.6) of index patients in the baloxavir group. However, no resistant virus was detected in household contacts. The researchers explained that, “All antiviral influenza drugs exert selective pressure on viruses, which can lead to the emergence of drug-resistant variants.” No new safety signals were identified in index patients treated with baloxavir.“Treatment with a single oral dose of baloxavir resulted in a lower incidence of influenza virus transmission to close contacts than placebo,” the authors concluded. But as most household members in this trial were unvaccinated, it “remains unclear how prior vaccination may affect the incidence of transmission after baloxavir treatment.”Reduced transmission would be an additional benefit of antiviral treatment during seasonal influenza epidemics, the authors noted.Indeed, their results show that, while vaccines remain the main measure for controlling influenza epidemics and pandemics, antiviral drugs play a complementary role, particularly in seasonally unvaccinated individuals.“In the event of a pandemic, vaccine development would take time, and the availability of an antiviral drug reducing disease severity and person-to-person transmission could be a new element in the fight against such a pandemic,” they wrote.This article has been translated from its original French and first appeared on our sister site Profession Santé.

Should antivirals play a bigger role in reducing family transmission influenza?

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