The closings announced Thursday follow dozens of others in recent weeks. City officials say the closed schools reported unusual numbers of students with flu-like illnesses.
The newly closed schools are: P.S. 83 and P.S. 182, which share a building in East Harlem; P.S. 503 and P.S. 506, which share a Brooklyn facility; and P.S. 155 in East Harlem. It includes P. 169, a school for disabled students.
The six schools will reopen Wednesday.
As many as four deaths have been linked to swine flu since the outbreak began in the city last month, though autopsies of two of the possible victims aren't yet complete. Authorities say most cases of the virus have been mild.
Separately Thursday, a U.S. health official said a swine flu vaccine could be available as early as October, but only if vaccine production and testing run smoothly this summer.
Dr. Anne Schuchat of the U.S. Centers for Disease Control and Prevention said the agency began shipping virus samples to manufacturers in the past several days. The government will have to review the safety and effectiveness of what's produced, and decide if a vaccination campaign is warranted. October is about the time seasonal flu vaccine campaigns generally get rolling.
CDC officials reported more than 8,500 probable and confirmed cases in the U.S., including 12 deaths and more than 500 hospitalizations.
The latest deaths from the virus were reported in Mexico - where the outbreak is believed to have started - today.
Mexico reported six more deaths from swine flu, bringing the country's toll to 95.
The Health Department says that 4,974 people have been sickened nationwide. That number includes the 95 deaths.
Health officials say 34 percent of those who died were obese and diabetic.
Mexico says its epidemic has largely subsided, but the confirmed toll has been rising as scientists test a backlog of samples from patients.