“Two critically important issues in human immunodeficiency virus (HIV) therapeutics are when to start antiretroviral therapy and how well these medications restore immunity,” writes Dr. Timothy Schacker of the University of Minnesota in a recent issue of JAMA Internal Medicine. He is commenting on a study done by the National Institutes of Health, also published in that issue, that looked at when HIV patients started taking antiretroviral meds, and how that correlated with their immune health later.

The researchers studied the data of more than 1,000 patients enrolled in the U.S. Military HIV Natural History Study between 1986 and 2010. They noted how soon patients started taking antiretrovirals after seroconversion—the point after HIV infection at which antibodies to the virus can be detected in a person’s blood. To measure immune health, the researchers looked at patients’ levels of CD4 T-cells—a kind of white blood cell. When people taking antiretroviral medication see their CD4 counts increase to 500 cells per microliter of blood, that is “typically regarded as optimal immune recovery,” the study says.

But it’s not perfect. According to the study, in healthy, HIV-negative people, that count is more like 900 cells per microliter. So HIV-positive people whose CD4 counts are higher than 500 but lower than 900 cells per microliter could still have a less-than-ideal immune system and be at increased risk for developing AIDS, even if they’re taking the drugs. So for the purposes of this study, 900 cells per microliter was seen as the ideal target that doctors should shoot for when treating patients using antiretrovirals.

Starting antiretroviral treatment within a year or less of seroconversion was associated with better outcomes for the patients, especially if their CD4 levels were at least 500 cells per microliter when they started treatment. These people had a higher chance of getting to the 900 cells per microliter “normal” level and were subsequently at lower risk of developing AIDS. This wasn’t a guarantee—only about a third of patients who started the medication within a year of seroconversion reached normal CD4 levels.

Early intervention might also be easier said than done. According to the Centers for Disease Control and Prevention, one in five people with HIV in the U.S. don’t know they have it. When the infection is still new, they might not be symptomatic, or they may mistake their symptoms for something else. What's more, only one in three adults, and one in four children, have access to antiretroviral medications.

“The importance of a public health strategy that includes frequent HIV testing in persons at risk and prompt initiation of [antiretrovirals] after diagnosis is underscored by [these] two findings,” the study reads.

In his commentary, Schacker notes that while this research shows a step that can be taken to increase some HIV patients’ health, it’s far from a perfect treatment protocol.

“Even if we were to accept a score of only one-third of persons as a success, it is unrealistic to think that we will routinely identify patients within 12 months of infection, especially in the parts of the world where this disease is most prevalent,” Schacker writes. “This sobering observation underscores the need to better understand the pathogenesis of HIV infection and use that information to inform drug discovery and rational policies for treatment.”