Hundreds of people who were given a shot of the COVID-19 vaccine at a New Haven clinic will need another jab after health officials said late Friday that vials of the Pfizer vaccine were improperly refrigerated.

As many as 650 people were administered shots of the vaccine over a 6-week period between Dec. 23 and Feb. 7 at a New Haven Health Department clinic, according to the Hartford Courant.

Officials said the efficacy of the doses might have been diminished because vials containing the vaccine were kept at a temperature below what is recommended.

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“After consulting with Pfizer and the Connecticut Department of Public Health it was recommended that those who received the improperly stored Pfizer vaccine or booster get revaccinated as soon as they can,” Health Director Maritza Bond said.

There’s no evidence that the temperature discrepancy has caused medical harm. The city said it is reviewing its policies and procedures of vaccine storage, and conducting an internal investigation.