SAN DIEGO -- The first round of swine flu vaccines are due in San Diego County next week, but some say a critical group is missing from the priority list.

The state of California will receive 350,000 vaccines, and the county will receive 28,000 doses of the vaccine next week.

County health officials said the priority list for the vaccines include pregnant women, children and young adults, people with underlying health conditions and health care and emergency services personnel.

The list does not include homeless citizens, 10News learned, and some homeless advocates are frustrated with the omission and call it a disaster in the making because the homeless survive by grouping together and sharing items, which may speed up the spread of any outbreak.

Bob McElroy of the Alpha Project said, "All it takes is one person, two people to get sick. It's just going to be devastating. Many are already physically ill. Their immune systems are shot and they're the most vulnerable. Because their survival is to group together, any virus would spread rapidly among the population; it would be tragic."

Stephen Johnson has been living on the streets of downtown San Diego for a year. He told 10News, "We're here and on the streets and in people's faces, but it's like we're invisible. We have to share everything to survive. We could be wiped out."

McElroy said he knows of no coordinated swine flu plan for the homeless, and he fears it could turn into a public health threat and a costly one.

"It's going to cost taxpayers a lot of money because these folks have to utilize the emergency rooms," said McElroy.

San Diego County Health Officer Dr. Wilma Wooten said they are simply following federal guidelines when it comes to identifying the most at-risk groups. She said the evidence and number of infected suggest dividing the categories by age instead of socioeconomic status.

"Homeless are vulnerable and they are a priority. Homeless children, young adults and those with underlying conditions are included in our priority list. There's also a plan in the works involving educational cards aimed at prevention and they will point the homeless to vaccine sites when those vaccines are available to them," said Wooten.