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Wer sollte Blut spenden dürfen?

von NFI Redaktion

At the peak of the pre-Delta variant of the COVID-19 pandemic, Stephen Rawlings, MD, PhD, was engaged in HIV and SARS-CoV-2 research when a couple of men approached him. Both were suffering from COVID-19 and wanted to donate convalescent plasma or otherwise contribute to help contain the virus. Rawlings had to turn them down.

For Rawlings and his principal investigator (PI), it was a bizarre moment. „Here was the private investigator, a gay man, I was a gay man, and there were these two men – and none of us could donate,“ said Rawlings. „But we were still forging better science in our own way.“

In this case, the potential volunteers could contribute antibodies but not whole blood. Since the early days of the HIV epidemic, gay, bisexual, and other men who have sex with men (MSM) have been barred from donating whole blood. In 2018, the US Food and Drug Administration (FDA) allowed gay men to donate blood if they were abstinent for twelve months. Then, in 2020, due to the impact of the COVID-19 pandemic on the blood supply, the FDA revised the policy again, shortening the abstinence period to three months.

Many, including White House officials, have recently argued that the current blood donation policy is outdated and unscientific. So, what could a more scientifically sound blood donation policy look like?

What we refer to as the US blood donor policy is actually a mix of criteria that individuals must meet before they are allowed to donate. It encompasses everything from medical and prescription histories to a series of questions about recent behavior, including questions about sexually transmitted diseases, non-prescription injection drug use, and recent tattoos. Additionally, men must not have had sex with another man in the last three months, and women must not have had sex with a man who has had sex with another man in the last three months. Once an individual clears all these hurdles, blood donation center staff, such as Impact Life which supplies blood to several dozen hospitals in the US, examine a person’s arms for needle marks. Assuming no red flags are found, „they lie down and bleed,“ said Dr. Louis Katz, Chief Medical Officer of Impact Life. The blood vials then go down the hall for blood typing and testing for everything from cytomegalovirus to West Nile virus, Zika, hepatitis B and C, and of course, HIV, „the prototype infection we worry about,“ said Dr. Jeffrey McCullough, global blood consultant and emeritus professor of laboratory medicine and pathology at the University of Minnesota Medical School.

While blood can now be thoroughly screened, McCullough said blood banks prefer to start with a clean sample rather than deal with issues later in the process. „We want to start with the highest-quality product,“ he said. And although there are now seven HIV tests available to screen the blood supply, including PCR, antigen, antibody, and nucleic acid tests, the tests are never 100% accurate, said McCullough. The question of how clean is clean enough is at the core: is a long abstinence period really necessary, or is there a better, more scientific way to reduce the risk?

McCullough said the current blood supply is the safest it has ever been, despite the three-month deferral for blood donation among gay and bisexual men. And Katz said that HIV transmission through the blood supply is so rare that scientists have to estimate it using models. As HIV testing and treatment have evolved over time, these models show that the risk of HIV entering the blood supply has decreased, said Dr. Brian Custer, Director of Epidemiology and Health Policy at the Vitalant Research Institute. In 1986, models suggested that one out of 22,000 blood units could contain HIV. More recently, these models estimate the risk of HIV entering the blood supply at 1 in 1.5 to 3 million.

However, the US blood donation policy is full of contradictions, said Jeff Crowley, former director of the White House Office of National AIDS Policy. Crowley, now a professor at Georgetown University Law School, described it as „hypocrisy“ within the current system. „With heterosexuals, we tolerate a high level of risk and with gay men, there is almost zero tolerance,“ he said of the original lifetime deferral policy. „If you were a heterosexual man having unprotected sex with a sex worker, you could be deferred for six months. But for gay men, it was a lifetime deferral. It just doesn’t make sense when trying to protect people.“

So, what would protect the greatest number of people most efficiently, with the lowest risk and the least discrimination? Science says.

According to CDC data, receptive condomless anal sex poses the highest risk of HIV transmission, followed by the role of insertion partner in condomless anal sex. Then, there is a higher risk with receptive partners in vaginal sex, and the least risk with two women having non-insertive sex. And while gay men are more likely to engage in receptive anal sex, they are not the only ones. A modeling study in 2020 in the American Journal of Reproductive Immunology suggested that 41% of new HIV diagnoses in American women were the result of condomless anal sex. There is also some data suggesting that the rectal mucosa of cis women may be more susceptible to HIV for unknown reasons compared to that of men.

And gay men are not the only ones contracting HIV. For example, in 2019 in the US, nearly a quarter of new HIV transmissions occurred in heterosexual adults. According to the CDC, 7% of new diagnoses were among people who inject drugs. However, the FDA is not currently reviewing deferral policies for heterosexuals with a higher risk of HIV, said Custer. Blood donation centers, though, discourage people from donating blood if they have engaged in sex work or drug use in the past three months.

A more scientifically sound approach might involve questioning each individual based on their sexual behavior. But that is not what the „Assessing Donor Variability And New Concepts in Eligibility“ (ADVANCE) study does. Conceived and funded by the FDA, the study considers additional ways to determine when gay and bisexual men can donate blood. The study asks gay and bisexual men questions about their sexual behavior, such as the number of partners they have had recently and whether they use condoms or HIV-prevention medications like pre-exposure prophylaxis (PrEP), said Custer. The study will not test these questions with heterosexual individuals.

„These are the questions that could one day appear on a future blood donor history questionnaire,“ said Custer. „A contemporary, science-based policy approach is what we aim to achieve.“

When the blood donation ban for gay men was put in place, there were no HIV tests. A ban was a blunt instrument. But it has long been replaced by precise HIV tests, said Katz. „By the late 1990s, we had nucleic acid tests – basically PCR – that could detect HIV within 7 to 10 days,“ he said.

And that should mean that a gay man who has been in a monogamous relationship for ten years where neither partner has HIV should be able to donate just as much as anyone else. „I am pretty confident that monogamous gay men can prove to be safe blood donors,“ said Katz.

Rawlings is such a man himself. „If I had a new sexual partner and that partner had unprotected sex in the past seven days, I should not have donated blood,“ he said. „The current policy does not account for that.“

This recommendation may contain a flaw, said Custer from the Vitalant Research Institute: HIV transmissions while someone is inconsistently taking HIV prevention medications, although rare, could lead to just enough drugs in the blood to maintain the virus level in the blood very low. It is unclear if current tests would detect this, he said. This is where the ADVANCE study comes in. In addition to questions about men’s sexual behavior and HIV testing, researchers will also test blood for concentrations of one of the most common PrEP medications, Tenofovir. After two weeks, participants will return to learn the results of the HIV test and fill out another, longer questionnaire about personal behavior. By correlating the concentrations of the drug with HIV tests, they hope to find out if this theoretical risk is an actual risk. Custer said they hope to receive study results early next year.

It is also possible, he said, that people taking PrEP may have a lower risk of donating HIV-infected blood since the medication is 99% effective in HIV prevention.

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