As thousands of Bay Area residents get the H1N1 vaccine, researchers say the drug is showing a "strong and robust" immune response in people.
Sanofi-Aventis of France is one of the manufacturers. The company reports patients were given the vaccine and checked during a six week follow-up period.
"It has not materially mutated over the summer and so this vaccine that we are giving now should be very efficacious," says Yan Chin, M.D., with the Current Health Medical Group.
However, in order to be this effective in children, the manufacturer is once again saying those under the age of 10 must be vaccinated twice. It is a recommendation given weeks ago by the Centers for Disease Control.
"We need that booster in order to get their immune system geared up to really protect them," says Chin.
"I didn't realize until today that we had to get two and so the next one is a month from now, but who knows if they have enough doses at that time. They say it might be until February before we get the second one," says parent Julie Ledbetter.
As of Wednesday, 38 million doses had been shipped to the different states. More should have arrived by now, but the virus used to produce the vaccine has taken longer to grow.
"It just hasn't been available through our doctor's clinic. So, I literally call every other day and check their website every day to see if they have in and it's just been out of stock," says parent Elizabeth Sutro.
In the meantime, to avoid the spread of the virus, doctors recommend good hygiene practices -- washing hands and staying home if you're sick.