Three years ago, Corey Walsh, who was in a relationship with a man who was HIV-positive, got a prescription for Truvada, a drug approved by the Food and Drug Administration to prevent infection with the virus that causes AIDS.

Walsh, then 23, was covered by his parents’ health insurance policy, which picked up the cost of the drug. But the price tag for the quarterly lab tests and doctor visits he needed as part of the prevention regimen cost him roughly $400, more than he could afford.

“I went back to my physician and said, ‘I can’t take this anymore because all these ancillary services aren’t covered,’” Walsh recalled. He ended up joining a clinical trial that covered all his costs.

Walsh’s experience with high out-of-pocket costs, whether for medication or related services, is common, advocates say. Last month, the U.S. Preventive Services Task Force recommended that clinicians offer prescription pre-exposure prophylaxis, or PrEP, to people at high risk of contracting HIV. The decision by the independent group of experts means that starting in 2021 most health plans are required to cover drugs that are recommended to prevent HIV, and patients can’t be charged anything out-of-pocket for the medication.

But the recommendation doesn’t apply to the other clinical and lab services people need if they’re on PrEP, according to task force officials.

In addition to the ancillary charges, other roadblocks persist for people who need PrEP from getting it.

“Eliminating cost sharing will undoubtedly expand access to individuals for whom affordability has been a significant barrier,” said Amy Killelea, senior director of health systems integration at NASTAD, an organization representing public health officials nationwide. “However, scaling up access to PrEP to individuals who need it most — including young, gay, black and Latino men — will require addressing other major systemic and structural challenges, such as stigma and provider awareness and willingness to prescribe PrEP to their patients.”

President Donald Trump has emphasized the need for more efforts to fight the HIV epidemic. In his State of the Union address in February, the president vowed to eliminate HIV transmission by 2030.

Currently, Truvada for PrEP, made by Gilead, is the only drug approved to prevent HIV. The once-a-day pill is at least 90% effective in some high-risk groups, including men who have sex with men as well as heterosexual men and women who have sex with HIV-positive partners, and 70% effective in people who inject illicit drugs.

Gilead estimated that 200,000 people now receive Truvada. The Centers for Disease Control and Prevention estimated that in 2015 there were 1.1 million people in the United States who could benefit from PrEP.

With a monthly price tag approaching $2,000, many private health plans have put the drug in a specialty drug tier with high copayments or coinsurance. Those payments will disappear when the task force recommendations take effect in 2021.

Truvada is generally covered in state Medicaid programs, as is the required clinical and lab work. But in the southern part of the country, where many states have not expanded Medicaid under the Affordable Care Act and HIV infection rates are high, there may be less access to the medication and other services.

Gilead offers a medication assistance program for uninsured people and a copay assistance program for those with private coverage that can fill gaps.

Gilead has submitted another HIV drug, Descovy, for FDA approval for PrEP, and a generic version of Truvada is expected next year.

It’s unclear how these options might affect people’s access to and ability to afford PrEP.

“Often it takes more than one generic for the price of a drug to drop,” said Jennifer Kates, a senior vice president at the Kaiser Family Foundation. (KHN is an editorially independent program of the foundation.)

The new preventive coverage requirement may lead to private insurers or Medicaid programs trying to limit access by imposing prior authorization requirements, some advocates worry. Insurers might, for example, require doctors to show that the patient is HIV-negative and meets the risk criteria before approving the prescription. That can have serious repercussions.

“Anytime there’s a delay at the pharmacy or on the provider’s end, patients will give up,” said John Peller, president and CEO of the AIDS Foundation of Chicago.