INDIANAPOLIS -- Health officials recommend all children get vaccinated against the H1N1 flu, but some parents are worried there might not be enough booster doses to go around.

Children need two doses of the vaccine for it to adequately protect them from the virus, 6News' Stacia Matthews reported.

More: H1N1 Special Section

"For most children through the age of 9, the vaccine will not be effective without that second dose," said Dr. Joan Duwve with the Indiana State Department of Health.

One dose will only protect a quarter of children six months to 3 years old, and only a half between 3 years old and 9 years old, Duwve said.

The Centers For Disease Control and Prevention recommends children get the booster within 28 days of the first dose, but it's important no matter when its administered, officials said.

"But if a child doesn't get that second dose for a month and half, two months, that second dose is still effective and also still necessary," Duwve said.

She said more pharmacies are now offering the H1N1 vaccine, along with doctor's offices, pediatricians and public clinics.