UPDATE 1-Pfizer sells China swine vaccine unit to Harbin Pharma

* Pfizer confirms sale of swine vaccine business

* Price tag seen at $50 mln - source

* Divestment a first under China anti-monopoly law (Add details and comments)

HONG KONG, May 31 (Reuters) - Pfizer Inc PFE.N, the world's biggest drugmaker, is selling its swine vaccine business in China to Harbin Pharmaceutical Group 600664.SS for $50 million, a source with direct knowledge of the deal said on Monday.

A spokeswoman from Pfizer’s Singapore office confirmed the divestment of its China swine vaccine business to Harbin Pharmaceutical but gave no details on the value of the deal or further comments.

“Pfizer did indeed divest,” the spokeswoman said.

Harbin Pharmaceutical officials were not immediately available for comment.

The disposal was required by the Anti-Trust Bureau of China’s Ministry of Commerce as a condition for approval of Pfizer’s $68 billion merger with Wyeth, which closed last October, said the source, speaking on condition of anonymity because the deal had not been officially announced.

The deal marked the first time China had ordered a foreign company to divest a locally-based business as a condition for approval of a merger with another foreign company, as part of a review under the country’s anti-monopoly law that took effect in August 2008, the source said.

Pfizer’s will sell its China operations to manufacture its RespiSure and RespiSure-One swine mycoplasma hyopneumoniae (MH) vaccines in the country, to Harbin Bio-Vaccine, an animal health unit of Harbin Pharmaceutical.

Business Development Asia (BDA), Clifford Chance, and King & Wood advised Pfizer on the deal, the source said.

Other bidders for the asset included Novartis NOVN.VX, Eli Lilly LLY.N, Boehringer Ingelheim, and Agenix AGX.AX, the source said.

Harbin Pharmaceutical, which counts Warburg Pincus [WP.UL] among its major shareholders, manufactures and distributes generic antibiotics in China.

Shares of Harbin Pharmaceutical have risen 21 percent so far this year, compared with a 19 percent drop in the key Shanghai Composite Index .SSEC. The stock was down 1.11 percent by 0542 GMT on Monday. (US$1=HK$7.8) (Reporting by Donny Kwok; Editing by Chris Lewis)