Harvard University Health Services expects its first delivery of H1N1 influenza vaccine to arrive in about two or three weeks, although the number of people being diagnosed with influenza-like illnesses at UHS has declined slightly this week, according to UHS officials.

When the vaccine arrives, UHS will first distribute it to groups designated as high-priority by the Centers for Disease Control and Prevention—including pregnant women, medical services personnel, and caretakers of young children—said UHS Director David S. Rosenthal ’59.

UHS has a list of about 300 to 400 people who qualify as high-risk according to CDC guidelines.

“Everyone wants to get it and will be clamoring for it,” Rosenthal said of the H1N1 vaccine. “If we have a limited supply, we need to make sure we get it to people who are high-risk first.”

The state has not given UHS many details about the arrival date of the vaccine or how much vaccine will be provided initially, beyond a promise that the vaccine would arrive “soon,” Rosenthal said, though he expects to receive a limited amount of the vaccine by the beginning of November.

About 300 people, mainly undergraduates, have been diagnosed with influenza-like illness by UHS since the end of August. Rosenthal said there have been about 50 new cases per week until this week, when there has been a slight decline in the number of people diagnosed.

The American College Health Association reports that regional outbreaks of influenza-like illness seem to have already peaked in the Northeast. There were 30 percent fewer new cases in Massachusetts last week compared to two weeks ago, according to the Association.

But Rosenthal said some healthcare professionals are anticipating two peaks.

“We just have to wait and see,” he said.

The Massachusetts Department of Public Health no longer recommends testing to distinguish H1N1 flu from seasonal flu, so students who have flu symptoms are simply diagnosed with an influenza-like illness. According to Rosenthal, testing at other colleges has revealed that 75 to 80 percent of flu cases are H1N1.

Massachusetts is not yet distributing injectable H1N1 vaccine, though the state has been giving out an intranasal spray vaccine with live H1N1 flu virus. Rosenthal said that UHS has only ordered injectable vaccines with dead virus because live virus is not safe for use in high-risk groups.

UHS continues to focus on isolating students diagnosed with influenza-like illness.

Students who live within two to three hours of campus are advised to recover at home, and students with single bedrooms can opt to return to their rooms.

Stillman Infirmary accommodates up to 15 students, and UHS has located 38 empty bedrooms throughout the House system in which to isolate additional sick students without single bedrooms.

—Staff writer Danielle J. Kolin can be reached at dkolin@fas.harvard.edu.