In 1996, while AIDS was  still a full-blown public-health crisis in the United States, the country was also in the midst of a prison-building boom. This got Grace Macalino thinking. A lot of prisoners have a history of injection drug use and engage in unprotected sex—key avenues of HIV transmission. How fast was the virus spreading behind prison walls?

Macalino, then a doctoral candidate studying infectious-disease epidemiology at the Johns Hopkins School of Public Health, wrote a grant proposal to find out how many prisoners were coming into Maryland prisons with HIV and hepatitis (another life-threatening blood-borne disease) as well as how many were contracting the viruses behind bars.

The Centers for Disease Control and Prevention gave her $1 million for the project, but then Maryland officials pulled out. So when Macalino joined Brown’s community health faculty, she turned to Rhode Island prison officials, who have long collaborated with Brown on inmate care, education, and research. Now, after more than two years of study, the assistant professor and her research team have found not only that inmates entering Rhode Island prisons have high rates of HIV and hepatitis but that male inmates are passing on hepatitis B at an alarming rate. (She has published her results in the American Journal of Public Health.)

Macalino and her team analyzed blood taken from 4,269 men between 1998 and 2000 as they entered the state prison. Nearly two percent of incoming inmates tested positive for HIV. (The virus is found in only .33 percent of the U.S. population.) Twenty percent of inmates had hepatitis B and 23 percent hepatitis C. (Five percent of the general public tests positive for hepatitis B and two percent for hepatitis C.)

When the researchers retested 446 inmates at least one year later, they found that   none had contracted HIV while in prison, and fewer than one percent had contracted hepatitis C. The spread of hepatitis B, however, was surprising. Almost 3 percent of inmates had contracted the virus—a rate higher than in any previous prison research and exponentially higher than the national average.

To treat these inmates, Macalino says,  prisons have a powerful tool at hand: a safe and effective vaccine for hepatitis B. Infants and toddlers are now routinely vaccinated to protect them against the disease, which attacks the liver and causes cirrhosis, cancer, and even death. As a result, Macalino and her colleagues recommend that prisons vaccinate all inmates.

Will prison administrators implement the recommendation? A recent survey found that only two facilities routinely give hepatitis B shots to inmates. Macalino says the reluctance to freely administer the vaccine is mainly a matter of money: prisons don’t have enough of it to give all inmates the three doses needed for full protection. But she believes the money—and the vaccines—will eventually arrive. “The question,” she says, “is who will step up and make it happen?”