The four companies, sanofi pasteur, MedImmune, CSL Limited, and Novartis Vaccines and Diagnostics, Limited, all have experience with immunizations, and used the same techniques to brew their batches of vaccines. ”The H1N1 vaccines approved today undergo the same rigorous FDA manufacturing oversight, product quality testing and lot release procedures that apply to seasonal influenza vaccines,” said Jesse Goodman, MD, acting chief scientist for the FDA.

As expected, the immunizations will be available to physicians by mid-October. Still, the flu season may be well underway in four weeks’ time, so the vaccine may come too late for some.

The US government has order 195 million doses of the vaccines. While recent studies have found one-shot efficacy in adults, children may still be recommended to get two doses. Some formulations are being made without the preservative thimerosal, which some parents distrust. There will also be a nasal-spray version available.