Baloxavir is effective for influenza prophylaxis in household contacts

Référence

Ikematsu H, Hayden FG, Kawaguchi K, et al. Baloxavir marboxil for prophylaxis against influenza in household contacts. N Engl J Med 2020;383(4):309-320.

Sommaire

These researchers identified index cases of influenza in Japan, and then recruited household members who were asymptomatic and had lived in the same household for at least 48 hours prior to ther housemate's diagnosis. The participants were randomized to receive a weight-based single dose of either baloxavir or placebo, usually taken within 24 hours of the index patient's diagnosis; this was a Phase 3 trial. All index patients were treated with an anti-influenza drug, and about one-third of all participants had been vaccinated against influenza. Approximately 75% of household contacts were adults, largely between the ages of 20 and 64 years, but the study also included children younger than 12 years, for whom baloxavir is not approved in the United States. The majority of index patients were children or adolescents (90.6%), while most of the contacts were parents of affected children (69%). There were a total of 545 index patients and 749 household contacts; approximately half the members of each household agreed to participate. Groups were balanced at the beginning of the study, allocation was concealed, and analysis included was by intention to treat (3 patients without symptom or virologic data were excluded). Patients' symptoms were recorded for 10 days and they had 2 nasal swabs for influenza polymerase chain reaction (PCR) testing. Patients in the baloxavir group were less likely to have a symptomatic, PCR-confirmed influenza infection than those in the placebo group (1.9% vs 13.6%; P < .001; NNT = 9). Among participants who became ill, those in the placebo group almost always became ill within 5 days, whereas those in the baloxavir group all became ill after 5 days. Mutations conferring resistance to baloxavir emerged in a small number of participants, although in some cases those participants appear to have been infected with virus that already had the mutation. Overall, the drug was well-tolerated with adverse events similar to placebo. This study may have issues with generalizability to settings other than Japan, given differences in household densities and mask-wearing behaviors even with routine respiratory infections.