Four vaccines are now approved by the Food and Drug Administration to fight against H1N1, also known as swine flu.

The vaccines are expected by mid-October. Doses will be available both with and without the preservative thimerosal.

Some parents have voiced skepticism about the forthcoming vaccines because of concerns about a possible link between vaccines containing thimerosal and autism. However, numerous scientific studies have disproved such a link and most vaccines now given to children do not contain the mercury-based preservative.

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Meanwhile, health officials say they are particularly concerned about children with disabilities who present with flu-like symptoms. Of the 36 children who died from swine flu by early August, two-thirds had a chronic illness or developmental disability such as cerebral palsy, developmental delay, muscular dystrophy, respiratory troubles or cardiac problems.

With that, officials at the Centers for Disease Control and Prevention are calling for children with disabilities to be among the first to receive the new vaccine.

In clinical trials of the now-approved H1N1 vaccines, most healthy adults responded to the vaccines within eight to 10 days of receiving a single dose, which is similar to the response to typical flu vaccines. Side effects were also similar to those found from the seasonal flu vaccines offered annually and included soreness near the injection, slight fever, body aches and fatigue.

Researchers are still conducting clinical trials to determine the dosage appropriate for children.