MedImmune, the global biologics arm of AstraZeneca, announced that it is restructuring its infectious disease and vaccines R&D and operations. This will result in the closure of MedImmune’s sites in Mountain View and Santa Clara, California.

The company estimates that approximately 300 jobs will be affected. Of those, approximately 100 positions will move to other MedImmune locations, including its Hayward, California site. The changes will not disrupt the delivery of the company vaccine supply, according to the company.

In February 2012, AstraZeneca announced an efficiency program to improve productivity, foster innovation, and strengthen the company’s commercial, operations, and R&D capabilities, which runs through 2014. The restructuring at MedImmune’s sites are part of that program.