Shares of China’s biotechnology firms plunged on Dec. 15 amid concerns that the Biden administration would put an investment and export ban on more Chinese companies. The decline was led by WuXi Biologics, which tumbled nearly 20 percent, while WuXi AppTec Co. slid 19 percent, and Sino Biopharmaceutical slumped 5 percent. The Hang Seng Healthcare Index fell almost 7 percent. The mainland index tracking the health care sector also slumped 3.2 percent, against a drop of 0.87 percent in the broader index. The declines followed a Dec. 14 report in Financial Times, which cited two people briefed on the plans, that said the Biden administration would add two dozen Chinese companies, including unnamed biotechnology firms, to a trade blacklist known as the “entity list.” Health care firms were already under pressure on Dec. 15 as Chinese biotech company BeiGene Ltd plunged in its Shanghai debut, amid concern that some Chinese firms …