Swiss drugmaker Roche’s brand of interferon can help control Hepatitis B, a potentially deadly liver infection, better than a competitor’s drug can, according to a new study published on Wednesday.

After 48 weeks of treating patients with Roche’s drug, researcher George Lau and his team at Queen Mary Hospital in Hong Kong found that Pegasys suppressed the virus better than British company GlaxoSmithKline Plc ‘s drug lamivudine.

A separate Hepatitis B study found a third drug, Foster City, California-based Gilead Sciences ‘s Hepsera, is effective only with continued use.

Its effects disappear within weeks after patients stopped taking the medicine.

The studies were published in the latest edition of the New England Journal of Medicine. The drug companies financed the studies, held and analyzed the data and more than half of the named authors had financial ties to those companies.

Some 400 million people worldwide are believed to be infected with Hepatitis B, which attacks the liver and can lead to liver cancer and death. The disease is caused by a virus, often spread through having unprotected sex or sharing needles with an infected person.

A handful of drugs have been approved to treat the condition, but their relative usefulness is a matter for debate, especially when treatment costs can range from $5,000 to $15,000 per year.

While patients treated with Pegasys suffered more side effects like depression, fatigue, headache, fever and muscle pain, the researchers said their finding supports the use of Pegasys, formally known as peginterferon alfa-2a, as a go-to drug for a common type of long-term hepatitis B.

The study of Hepsera, also known by the generic name adefovir dipivoxil, followed people with another form of hepatitis B, HbeAg-negative, which accounts for about 14 percent of U.S. cases and even more elsewhere.

A team led by Stephanos Hadziyannis of Henry Dunant Hospital in Athens, which has been following 185 volunteers, some of whom who have gone on and off the drug for as long as 144 weeks, discovered that Hepsera continues to work in more than two out of three patients.

However they found that when patients stopped taking the drug, the Hepatitis B virus became reactivated, with amounts of the virus returning to pre-treatment levels within a month.

“Long-term therapy will be needed for the majority of patients,” they concluded.

In a Journal editorial, Anna Suk-Fong Lok said she was disappointed that the treatment did not wipe out Hepatitis B from the body.

The Hadziyannis team also reported in the Journal that after nearly three years of treatment, only 6 percent of patients had developed a mutation that made the virus resistant to the drug. By comparison, when lamivudine is given, the drug typically loses its effectiveness in 20 percent of patients each year.