Swiss pharma company Novartis has raised its bid to purchase Emeryville, CA–based vaccine maker Chiron. In a written statement, Chiron said the new bid was added as an amendment to the existing merger agreement, making the deal now worth roughly $5.4 billion, versus the older offer of $5.1 billion.Novartis already owns a 44% stake in Chiron. Shareholders in Chiron are slated to meet on April 12 to discuss further the takeover. A shareholder vote is scheduled for April 19.