(Bloomberg) -- Biotech companies that are chasing treatments and vaccines for Covid-19 tumbled Monday after positive news about Pfizer Inc.’s inoculation.

Smaller vaccine developers such as NantKwest Inc. and Inovio Pharmaceuticals Inc. fell after study results from Covid-19 shots from Pfizer and its German partner BioNTech SE showed that they could prevent more than 90% of infections. Many of these smaller drug developers have yet to develop a successful treatment of any kind and have seen triple or even quadruple digit share gains so far this year.

NantKwest slumped as much as 16%. Inovio sank as much as 15% -- the company’s Phase 2-3 vaccine study was put on a partial hold in September. Humanigen Inc., which is developing a treatment for a potentially lethal side-effect of the virus, and Sorrento Therapeutics Inc., which has been touting results for its antiviral treatment in hamsters, also fell 15% each.

Vaxart Inc., which is testing an oral vaccine, tumbled as much as 20%.

Moderna Inc. which, like Pfizer, is working on messenger-RNA vaccines, rallied 9.3% on the heels of Pfizer’s success. Novavax Inc., which is expected to start a late stage-study later this month, briefly plunged 11% premarket Monday but then rallied as much as 10% after revealing its vaccine received fast track status in the U.S.

(Updates shares throughout)

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