Hundreds of thousands of doses of the H1N1/swine flu vaccine are being recalled, because they may not be effective enough to protect against the virus.

The Centers for Disease Control has issued a recall for about 800,000 doses made by Sanofi Pasteur.

The affected vaccines are pre-filled syringes for children aged six months to almost three years old. According to the CDC, the doses were sent all over the country, and it is reaching out to providers who received to notify them not to use any of the remaining supplies.

Health officials say children who already received the dose likely will not need to be re-vaccinated. They say the lots passed potency tests when they were first shipped, but decreased later.

City health officials say they are still waiting to hear if any of the recalled doses were sent to the five boroughs.

(Source: NY1)