Crowds totaling more than 1,000 people in some places are waiting hours to get vaccinated.
The Center for Disease Control says 12 million of the 250 million doses ordered have been made available.
Health officials promise there will be enough vaccines to go around soon, but many-- including lawmakers-- are wondering why it's taking so long.
While the government continues to map out and monitor response to the H1N1 vaccine, Americans are waiting in long lines to get the shot.
"It's not even just the fact of how sick they would be and the suffering, but the fact that people are dying from this and children are dying from this, there's no other choice than to do this," said Maryland parent Susan Schwartz.
"It just seems like there's an increasing number of children and young adults that are getting infected by the swine flu so my husband and I made the decision that it was critical to get vaccinated and especially our daughter," added mother Nyla Devall.
The government says vaccine production is "behind schedule," but health clinics and doctor's offices are getting more doses each day.
There's a search for answers on Capitol Hill, as a Senate panel questions top administration officials.
"Am I right that there is not now enough vaccine to vaccinate every american who now wants to be vaccinated?" asked Sen. Joe Lieberman.
Sen. John McCain also wondered, "when will all states be caught up?'
Health Secretary Kathleen Sebelius, recovering from recent eye surgery, insisted they're doing all they can.
"The goal is to get the vaccine out as fast as possible, and get as many people, particularly, start with the high priority groups, but get to everyone who wants a dose," she responded.
Manufacturers say they will have enough doses for everyone who wants the vaccine by mid November.
Experts recommend those not considered to be at a greater risk of getting the virus wait.
"We will be having these clinics for weeks and weeks and weeks to come and we're asking the general public who aren't in those target groups to hold back and let those people in the high risk groups get the vaccine first," said Mary Anderson of the HHS.
They also stress the importance of taking precautionary measures to prevent the flu from spreading even more - like using hand sanitizers and covering your face when you cough, as the secretary displayed during the hearing.