WASHINGTON — A major international study says don’t delay in seeking HIV treatment: Starting medication soon after diagnosis helps keep people healthy longer.

People who started anti-AIDS drugs while their immune system was still strong were far less likely to develop AIDS or other serious illnesses than if they waited until blood tests showed their immune system was starting to weaken, the U.S. National Institutes of Health announced Wednesday.

The findings are preliminary, but the NIH found them so compelling that it stopped the study a year early, so that all the participants could receive medication as researchers continue to track their health.

How soon should treatment begin? “The sooner the better,” said Dr. Anthony Fauci, director of NIH’s National Institute of Allergy and Infectious Diseases.

The findings support current U.S. guidelines that already recommend early treatment for HIV, but could alter care recommendations in other countries.

HIV may not trigger symptoms for years, begging the question of how soon after diagnosis expensive medications that may cause side effects should be started. Previous studies have made clear that treatment dramatically lowers the chances that someone with HIV spreads the virus to a sexual partner. But there was less evidence that the HIV patient’s own health would benefit.

In many poor countries, people are often sicker before they receive treatment. Even in the U.S., many people don’t seek or stick with early care.