The US Food and Drug Administration is considering a requirement for blood banks to use a new test that can detect the parasites that cause malaria in certain donors’ blood, and it’s seeking the opinion of its independent advisers on the best way to meet its goal of zero transfusion-related cases without unnecessarily prohibiting some people from donating blood.
The World Health Organization says malaria is a significant global health issue, with 249 million cases and more than 608,000 deaths in 2022 alone.
Malaria is not considered a big threat to the US blood supply like it is in some other countries. But nearly 28 million US residents travel to parts of the world where malaria is common each year, the FDA says, and as more Americans travel and as the planet gets warmer, scientists have predicted that the disease could become more likely in the US, even with aggressive mosquito control.
As late as the 1940s, the US Centers for Disease Control and Prevention said Thursday in a presentation to the FDA’s advisory committee, the US had about 65,000 cases of malaria a year – but that changed when the country needed healthy service members to fight in World War II. Knowing that many would train in malaria-prone areas in the South, President Franklin Delano Roosevelt’s government waged a war on mosquitoes that paid off.
By 1949, according to the CDC, malaria was no longer considered a significant health problem in the US, and WHO declared the US free of the disease in 1970.
The US still has about 2,000 cases a year, according to the CDC, but most are travel-related.
The CDC noted that although the risk of locally acquired malaria in the US continues to be “extremely low,” just last summer, it warned doctors to watch for locally acquired cases. There were a handful of non-travel-related cases in Texas, Florida, Maryland and Arkansas last year, the first locally acquired malaria cases in the US since 2003.
In March, the FDA approved the first test intended to screen donor blood for the evidence of malaria. The Cobas malaria test, made by Roche, can detect RNA and DNA from the parasite that causes malaria in donor blood, organs and tissue.
Malaria transmission through a blood transfusion is not common, but an infection can trigger severe symptoms and even death, studies show. A CDC study found that from 1963 through 1999, there were just 93 cases spread through donated blood in the US, but 10 of those people died.
Another study found 13 malaria cases related to blood donations between 2000 and 2021, the FDA said, but seven of the cases involved donors who met current FDA eligibility criteria.
“It’s complicated, and it doesn’t prevent all cases,” Jennifer Scharpf, associate director for policy in the agency’s Office of Blood Research and Review, said of the current guidelines.
The FDA told the committee Wednesday that its current guidance comes with a high level of “complexity” and that blood bank workers must assess several potential risk factors.
Blood banks use a donor history questionnaire to screen for people who have had malaria or who lived in a country where the disease is endemic in the past three years. People are also deferred from donating if they have traveled to a country with endemic malaria in the previous three months; or if they were a resident of a malaria-endemic country, if they have spent less than three consecutive years in a country where malaria is endemic, or if they have a history of travel to a malaria-endemic area in the previous three years. The rules are slightly different for platelet and plasma component collection.
These questionnaires have limitations, and the screening process is “error-prone,” the FDA said. Deferral periods may also not be sufficient to catch asymptomatic donors, particularly for residents of countries where malaria is common, because they may have partial immunity from a previous infection.
On the other hand, the current guidance disqualifies a large group of healthy potential donors, the FDA said. Some estimates say that between 1% and 3% of all donors are turned away based on travel history alone, and blood banks say they can never get enough donors.
Scharpf told the committee that about 50,000 to 160,000 donors may be deferred annually, and studies show that many people who are deferred often don’t return, even when they are eligible to donate.
The FDA is considering a couple of strategies to update its guidelines.
The first consideration is to do selective testing of a donor’s blood based on their history of malaria infection, having traveled to a malaria-endemic area in the previous three months or having ever lived in a malaria-endemic country. Another option is to test all donors at least one time and then to selectively test donations from people at risk of exposure, including those who had ever had malaria and those who had traveled to a malaria-endemic area in the previous three months.
Most of the advisory committee members seemed to favor the first option, saying the second seemed like overkill.
“It’s such a low incidence of disease, and it’s treatable,” said committee member Dr. Richard Scanlan, a professor, vice chair of the Laboratory Medicine Transfusion Service and medical director at Oregon Health & Science University.
The FDA is also considering requiring testing of all blood donated in areas where there was even one locally transmitted malaria case recently, but the committee members seemed less sure about this idea.
Committee member Dr. Sanjay Ahuja, director of Rainbow Hemostasis & Thrombosis Center at Rainbow Babies & Children’s Hospital in Cleveland, said that if there is proven local transmission, the decision of when to test all donor blood from the area is a “difficult one.”
“There are so many nuances to this,” Ahuja said. “I think it might be a little bit much in my opinion, but I don’t know whether more evidence of local transmission should be in place before we say ‘yes’ to this.”
During the meeting’s public comment period, leaders of some blood supply organizations encouraged the FDA to take a cautious approach to changing the guidelines.
Ralph Vassallo, incoming chair of the Association for the Advancement of Blood & Biotherapies Transfusion Transmitted Disease Committee, said his group joins America’s Blood Centers and the American Red Cross in believing that the new test for malaria holds real promise to improve blood safety and may improve the availability of donors by removing “unnecessary donor deferrals,” particularly among subsets of donors with uncommon blood types, such as those from Latin American, Asian and African countries.
But, he told the committee, there are no clinical studies that show that the test reduces the risk of transfusion-transmitted malaria.
Vassallo also encouraged the FDA to use flexible testing strategies and said that although the groups supported limited testing of all donations in ZIP codes with local malaria transmission, one case should not be enough to trigger such testing.
“FDA should support formal modeling studies designed in consultation with malariologists using the best available assumptions about parasite levels during asymptomatic infection before issuing final guidance,” he said.
The committee did not vote on the proposed strategies, but the FDA said it would take the discussion into consideration as it considered changing its guidance.