Researchers say influenza may be becoming Tamiflu-resistant

A research team in Singapore has found that influenza may be becoming resistant to the Tamiflu vaccine.

Although the World Health Organization has declared the swine flu pandemic over, the H1N1 virus still exists in some parts of Asia, particularly in India.

The study, held by doctors from the Agency for Science, Research and Technology in Singapore, was initiated after a Singaporean woman’s virus mutated into a drug-resistant form overnight, according to the

Masafumi Inoue, lead author of the study, told that his team’s medical data showed that resistance to oseltamivir - the generic name of Tamiflu - developed within two days.

The discovery was made by Dr. Timothy Barkham, a senior consultant in laboratory medicine at Tan Tock Seng Hospital, after a previously healthy 28-year-old patient displayed resistance within 48 hours after she was given Tamiflu.

Barkham reported the mutant H1N1 strain was not present in the patient at the initial point of infection.

Barkham told that while increasing numbers of drug-resistant strains of pandemic flu are being reported, most of the early examples had been found in immunosuppressed patients who have weakened immune systems. Barkham also said that, in most cases, it takes four to 14 days of treatment to develop the resistance.

“As with all antimicrobial medicines, we should not give patients anti-viral drugs unless it is really necessary,” Barkham told, noting that antivirals are likely to be most effective for a more severe flu but may have limited benefits in mild infections.

Drug resistance to Tamiflu, which is manufactured and distributed by Roche and Gilead Sciences, was initially reported in 2008.

“Whatever the epidemiological data exhibit, clinicians should consider resistance when patients do not respond to treatment for pandemic 2009 because H275Y can emerge literally overnight, as the case reported here reminds us,” Inoue said, reports.

The study findings were recently detailed in the journal Emerging Infectious Diseases.