AstraZeneca's announcement that it paused a study of a Covid-19 vaccine candidate after a patient suffered a serious side effect shook the stock price — and put a dent in investor optimism of a speedy end to the pandemic.

Barry Norris, chief executive of Argonaut Capital, and manager of the Argonaut Absolute Return Fund, says he is short healthcare stocks including Novavax and Inovio, saying he made those bets because market expectations of a vaccine are misplaced.