The Centers for Disease Control and Prevention says there is not enough H1N1 vaccine available for everyone in the United States. And schools and clinics around the U.S. are experiencing the results of the shortage.
It is a frightening experience for some children, but their parents consider them fortunate.
"You talk about it ahead of time and make sure they understand they need the shot," Tim Rigby explained, "that they're going to get the shot."
The original plan was to vaccinate every elementary age student, with their parent's approval. But nurse coordinator Robin Wallin at Alexandria public schools outside of Washington now has to tell parents only children in pre-kindergarten through first grade can receive the H1N1 vaccine.
"The biggest problem that we've had is that our supply has not come in as fast as we have anticipated," Wallin said.
Desperate parents trying to find the vaccine at clinics and other places are having a difficult time.
"They been calling all over trying to find it and they're so upset now it's not available but hopefully more will come," Tiffany Scruggs said.
Parents are upset because of the statistics. Health officials say more children have died from the H1N1 flu this year than from the regular influenza during an entire flu season.
In some cities, people wait for hours at mass vaccination clinics, just to be turned away when the supply is gone.
Pregnant women, health care workers and young children get the vaccine first. Many parents want to know when the next batch of vaccines will arrive for their older children.
"We're telling them we don't know," Wallin explained, "because we're really dependent on the vaccine arriving and we have no control over that."
Health officials say the H1N1 vaccine is difficult to grow, and that causes a delay in production and a shortage of vaccine. The CDC says there are now more than 22 million doses available, but there eventually will be some 225 million doses.
Because of the shortage, Tiffany Scruggs says her pediatrician advised her to have her son vaccinated as soon as possible.
"He told me he didn't have it available," she said, "so if the school did it's best to get it now than not be able to get it when I need it."
CDC director, Dr. Thomas Frieden says that is another reason why there aren't enough vaccines.
"It's quite likely that too little vaccine is one of the things that's making people more interested in getting vaccinated, frankly," Dr. Frieden said. "When we have shortages, we see an increase in demand."
The CDC expects the H1N1 vaccine to be widely available to the public by the beginning of December.