 The biotechnology exchange-traded fund SPDR SP Biotech ETF NYSE: XBI is up around 50 in 2020 and Jefferies managing director Michael Yee says the valuations are not only justified but sustainable in 2021. Exciting stories for 2021 While looking at the Biotech sector, it is important to separate the small group of COVID-19 vaccine makers from the overall biotech innovation thesis, Yee said Tuesday on CNBCs Closing Bell. 