San Francisco County officials said that parents do not need to worry because it is not a safety issue. The problem with the doses that were recalled has to do with their strength.
A pediatric H1N1vaccine in pre-filled syringes tested fine when it was shipped out earlier this fall. But last week, testing of several lots showed the potency had dropped.
"The level of antigen, which is the protein in the vaccine which creates the immune response, was a little bit lower than required," said Dr. Susan Fernyak from the San Francisco Health Department.
San Francisco received 9,000 doses of the shots that were recalled. But the county doesn't know how many were given because a lot of doses went to hospitals and private practitioners.
Santa Clara County says it received 900 doses and almost all have been administered. Marin, San Mateo, Contra Costa and Alameda counties did not receive any of the recalled lots.
This version of the H1N1 vaccine was only administered to children three years and younger.
Mark Mosquera, whose son was vaccinated, is a bit concerned.
"Well you know, it worries me a little if the dose is not that strong," he said.
But Fernyak says Mosquera and other parents need not worry.
"Children who already received the vaccine are going to have an adequate immune response," she said.
Young children are supposed to get two doses, spaced about a month apart.
Santa Clara County Health Officer Dr. Marty Fenstersheib says those who got the recalled shots still need to get the second dose.
"If they got their vaccinations as their second dose, we're confident that that was sufficient and they don't need a third dose of vaccine," he said.
Winsome So echoed the feelings of several parents we spoke with.
"We're just happy that we got the dose in the first place," she said.
Health officials are telling parents not to worry if their kids got one or two doses of the shots, because they said that the vaccine is safe. They are still encouraging parents to get their kids the vaccine at clinics.
Since October, 95 million doses of swine flu vaccine have been available in the U.S.
Again, the recall impacts 800,000 syringes of the vaccine intended for children from the ages of six months to 3 years old. Nearly 48,000 of those doses were sent to California.