Novartis’ proposed acquisition of vaccine and biologics specialist Chiron was granted a green light by the European Commission yesterday.

The go-ahead keeps the transaction on schedule to complete in the middle of this year, although opposition to the $5.1 billion deal has been voiced by some of Chiron's shareholders, who claim the offer undervalues the company.

The link-up has already been approved by the US Federal Trade Commission (FTC), and is now subject to stockholder approval and other customary conditions, said Novartis.

The Swiss drugmaker intends to combine Chiron with some of its in-house businesses to create a vaccine and diagnostics division, headed by Joerg Rheinhardt, currently Novartis' global head of pharma development. Chiron's biopharmaceutical business will be subsumed into Novartis' pharmaceutical division.