They were crucial for vaccines against hepatitis A and B. They took part in hundreds of early studies of HIV. And in 1961, two of them were shot into space.

But the role of chimpanzees in medical research is at a crossroads. Last week, the highest scientific body in the land put the issue on trial as a committee of the Institute of Medicine, part of the congressionally chartered National Academy of Sciences, met to deliberate the fate of nearly all of the world’s remaining medical research chimps.

The European Union banned the practice last year, leaving the United States and Gabon as the only countries conducting medical research on chimpanzees. At drug companies, chimp research is waning with the emergence of lower-cost, higher-tech alternatives.

“If you’re a scientist, a chimp is really a sort of last resort,” said Harold Watson, who directs the chimpanzee research program at the National Institutes of Health, which manages 734 of the nearly 1,000 medical research chimps in the United States.

Last year, the issue blew up at NIH. That’s when the agency announced it would move 200 older apes from a facility in New Mexico to an active research lab in Texas. A parade of politicians, activists and famous faces — including former New Mexico governor Bill Richardson (D) and chimpanzee champion Jane Goodall — mounted an uprising. NIH relented, transferring just 14 of the animals before charging the Institute of Medicine with arbitrating the issue in January.

The Institute of Medicine will issue its findings by the end of the year. Although Watson said NIH officials would “pay attention” to the recommendations — which could include ending all medical research on chimps — he declined to predict the agency’s response. “I can’t tell you what impact [the report] is going to have,” he said.

Already, though, chimps — expensive, difficult to handle and so like humans — are falling out of favor with researchers.

From 2007 to 2010, the number of biomedical chimp studies conducted in the United States declined from 53 to 32, said Robert Purcell, a virus researcher at the National Institute of Allergy and Infectious Diseases, part of NIH. Just one of those studies involved HIV — which in the 1980s and 1990s was extensively studied in apes. None of the studies involved cancer.

“Use of chimps for HIV decreased dramatically as [research] migrated over to rhesus monkeys,” which more faithfully reproduce human HIV infections, Watson said.

At any given time, 20 percent of available chimps are being used in medical studies, Watson said.

One big reason for the drop: Drug companies are forgoing chimp studies. In 2008, GlaxoSmithKline announced it would no longer use any apes. Biotech giant Genentech also ended the practice, said Theresa Reynolds, director of drug safety assessment at the company. “With advances in technology, chimps are no longer necessary” for developing high-tech drugs called monoclonal antibodies, she said. Before the Institute of Medicine meeting, Reynolds informally polled executives at “six or eight” other biotech firms; none use chimps.

A major international effort to develop a malaria vaccine also eschews apes. “It has worked well to work in mice and then move to monkeys, not chimps,” said Ann-Marie Cruz, program officer at the PATH Malaria Vaccine Initiative.

But chimp research still has its champions. The animals are vital for developing drugs and vaccines against hepatitis C, Purcell said; about 75 percent of ongoing chimp studies involve hepatitis C. The virus, which is carried by 3.2 million Americans and often causes liver cancer, infects no other lab animal.

“It’s also important to keep chimps available for diseases we haven’t seen yet, future ‘Hot Zone’ agents we can only speculate about,” Purcell said.

Many of the hepatitis studies take place at the Texas Biomedical Research Institute in San Antonio. A scientist there, Robert Lanford, said that testing new drugs and vaccines in chimps “increases success in the clinic” by weeding out ineffective or unsafe candidates.

NIAID researcher Peter Collins pointed to chimps as the only species for testing vaccines against respiratory syncytial virus, which infects infants and the elderly. Like hepatitis C, RSV does not infect rats or mice.

In the fictional laboratories depicted in the film “Rise of the Planet of the Apes,” “humanized chimps” revolt. In real laboratories, though, it’s “humanized mice” that may set free the medical chimps.

These engineered rodents carry tiny human livers, which succumb to hepatitis C, said Alexander Ploss of Rockefeller University. Some versions of the mice also live with human immune systems, which render their infections more like those seen in people.

“We are more than halfway” to mice that could replace chimps in hepatitis studies, Ploss said. “Whether we have that mouse in two years, five years, 10 years . . . who knows?”

In directing the Institute of Medicine committee, NIH officials were explicit in their charge: They asked the committee to examine only the scientific value of chimp research. But Thursday, committee members made clear that ethical issues are also in play.

They arranged for Goodall — for decades the world’s most prominent chimp advocate — to speak from Britain.

“From their point of view, it’s like torture,” Goodall said of chimpanzees kept captive for developing new medicines. “They are in prison and have done nothing wrong.”

A short time later, Eugene Schiff, a hepatitis researcher at the University of Miami, said, “I’ve never worked with chimps, but just listening to Jane Goodall, I got a guilt trip.”

Humanity, it seems, is on a collective guilt trip. “Rise of the Planet of the Apes” is a blockbuster. And in April, Rep. Roscoe G. Bartlett (R-Md.) and Sen. Maria Cantwell (D-Wash.) reintroduced the Great Ape Protection and Cost Savings Act, which would ban “invasive research” on great apes in the United States.

“We wouldn’t be having this meeting if ethics wasn’t an issue,” Frans de Waal told the IOM committee. The Emory University researcher, whose pioneering studies with captive chimpanzees have revealed their human-like empathy, continued, “We don’t have this kind of meeting about rats.”