U.S. drugmaker Pfizer Inc (PFE.N) said on Thursday it will cease its vaccines sales operations in China after an import license for one of its top-selling treatments, the only vaccine it sold in the country, was not renewed. A Pfizer spokeswoman declined to say why the Chinese import license for Prevenar, an anti-bacterial treatment, had not been renewed. The China Food and Drug Administration regulatory agency could not immediately be reached for comment. The move comes as drugmakers face growing difficulties obtaining approvals for medicines in China, the world’s No.