"A brief shortage of OS is expected through mid-January. We may be unable to fill complete orders from distributors for a limited time," [Roche spokeswoman Tara] Iannuccillo added.
Tamiflu is used to reduce the severity of the flu when taken at the outset of symptoms. The oral suspension of the drug is primarily prescribed for children under the age of 13 and for people who have difficulty swallowing.
The delay in packaging of the liquid version has not impacted supplies of regular Tamiflu 75 milligram capsules, Genentech said.
The flu is spreading quickly this season, with 25 states already reporting cases, according to the U.S. Centers for Disease Control and Prevention.
Thousands of people die every year from flu, which typically peaks in the United States between the months of October and March. This season's virus has killed six children in the United States so far, according to CDC data.
Roche said it expects to have additional supply of Tamiflu OS available in mid-January.
"We expect that these new supplies should meet demand for OS overall and we will continue to receive and ship out new supplies of Tamiflu OS and capsules throughout the flu season," Iannuccillo said.
If the drug is unavailable in a particular area during the shortage, pharmacists can mix the capsules into an oral suspension for people who need it.
Meanwhile, the CDC is recommending that people continue to get flu shots to prevent the virus.
Image: Child with flu waiting for medicine, via Shutterstock