Researchers have found that a single dose of the antiviral flu drug -- baloxavir marboxil -- can reduce the spread of the illness within households. For the study, published in the New England Journal of Medicine, the research team examined household contacts of 545 patients with the flu.

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They found that flu infections were much less common in household members who received the drug than among those who received a placebo. Only 1.9 percent of uninfected household contacts who took a single dose of baloxavir marboxil came down with the flu, compared with 13.6 percent of those who received the placebo, according to the research. "This trial established that baloxavir, if taken within a day or so after exposure, is highly effective for preventing influenza illness in households, a high-risk setting for virus transmission," said study researcher Frederick G Hayden from the University of Virginia in the US. "The findings indicate that baloxavir prophylaxis should prove effective for prevention in other circumstances, such as outbreaks in nursing homes and healthcare facilities, although formal studies will need to be undertaken," Hayden added.

The US Food and Drug Administration has approved baloxavir marboxil to treat flu within two days of symptom onset in people 12 years and older and those at high risk of developing complications. Its approval in 2018 marked the first novel flu drug in 20 years. According to the researchers, the double-blind study found that baloxavir marboxil, sold under the brand name Xofluza, was effective in adults, children and those at high-risk, regardless of whether they had received the flu vaccine. The frequency of adverse events, such as headaches and nausea, was similar among those who received the drug (22.2 per cent) and those who received placebos (20.5 per cent). There were no deaths in either group.

Hayden, who was also part of a research team that published a month ago in Lancet Infectious Diseases, also found that baloxavir treatment shortened the duration of influenza and reduced complications in adults and adolescents at high risk of complications."A single dose of the drug was as effective as a five-day course of oseltamivir (Tamiflu)," the researchers concluded.