Though the FDA specifications for transfusion of blood permit the use of 42 days old blood but a latest research shows that patients given 29 days or longer stored blood transfusions were twice likely to get hospital- acquired infections.

The patients become prone to  urinary-tract infections, pneumonia and infections associated with intravenous lines.

"We're not talking about hepatitis, HIV or other things that are transmitted in the transfused blood, but an increased susceptibility to infection as a result of the transfusion," Dr. David Gerber of Cooper University Hospital, one of the researchers, told during an interview.

"There are significant policy implications for this. Transfusion is still an important medical practice," Gerber added.
It’s not the blood that gets infected but the stored blood releases chemical agents called cytokines which affect the recipients' immune systems. This makes them more susceptible to infections as per Dr. Raquel Nahra of Sparks Regional Medical Center in Fort Smith, Arkansas.

At the same time many experts fear that if new regulations regarding blood transfusion are implemented less blood will be available. This in itself would create problems for patients.