A lawsuit filed against Gilead Sciences alleges that the drugmaker mailed envelopes to HIV clients that compromised their privacy. The two plaintiffs in the federal class action case are from Alabama and Indiana, but it is not yet known how many customers received the mailing.

The lawsuit was filed in California (where Gilead is headquartered) by the AIDS Law Project of Pennsylvania along with Berger Montague PC and Langer Grogan & Diver P.C, according to a press release from AIDS Law Project.

According to the lawsuit, some Gilead customers received an envelope in the mail with “HIV Prevention Team” identified as the sender in bold red letters. One plaintiff said he is so intent on keeping his HIV information private that he refills his HIV-related med from a different pharmacy from the one he regularly uses—yet he received the Gilead envelope at his workplace.

The mailers were sent to participants of Gilead’s patient assistance program for its pre-exposure prophylaxis (PrEP) meds, which are taken by HIV-negative people to prevent them from contracting HIV (more details on this below).

In the press release, AIDS Law Project states that “in signing up for the Advancing Access Program, Gilead customers were promised confidentiality and did not expect or agree to receive mail from Gilead that would link them to HIV. Stigma surrounding HIV can lead to discrimination in employment, housing, education, and health care, and even violence. Fear of that stigma is widely recognized as contributing to the AIDS epidemic by discouraging people from getting tested. To ensure that people feel safe to come forward to be tested and treated for HIV, many states have adopted laws that protect the confidentiality of HIV-related information and provide for statutory damages.”

Gilead released a statement, reports the Philadelphia Inquirer, asserting that the error resulted from accidentally using the wrong envelope. “We regret that the envelope caused any concerns, and we apologize to anyone affected. However, we deny the assertions in the complaint and will file our response in a timely manner,” read the statement. It then added that “on discovering that an envelope template usually used for communications with health care professionals was inadvertently used for the consumer mailer in question, we took immediate action to address it, including to discontinue the use of this particular envelope.”

AIDS Law Project filed a similar class action lawsuit three years ago against health insurer Aetna for disclosing private health information about its clients in some of its correspondence. That case involved two mailers, one to people with HIV and another to those with a heart condition. Eventually, Aetna reached a $17 million–plus settlement with nearly 12,000 customers in several states and agreed to pay a $365,000 penalty in New Jersey.

The Gilead lawsuit seeks monetary compensation for the plaintiffs and class members; it also demands that the pharma company update its mailing procedures. You can read the full complaint as a PDF here.

In related POZ news, scientists estimate PrEP to be about 99% effective among men who have sex with men and greater than the current 88% to 90% estimate for heterosexual men and women. For more details, see “How Well Do U=U and PrEP Work? The CDC Updates Its Answers.” In the United States, PrEP is available as Truvada and Descovy tablets; both consist of two meds, and both tablets are manufactured by Gilead Sciences. For more details, see “What’s the Difference Between Truvada and Descovy for PrEP?