Early stage clinical trial results show the Covid-19 vaccine candidate made by Novavax is safe and elicits an immune response, according to a study published Wednesday in The New England Journal of Medicine. The results had previously been announced by the company in early August. Using a randomized, placebo-controlled trial -- the gold-standard method of study -- scientists gave the vaccine or a placebo, an inert substance like saline, to 131 healthy adults in May. At day 35, there were no serious or unusual adverse events. One person reported a mild fever that lasted for a day after the second shot. Otherwise, most didn't have any reaction at all, or if they did have a reaction, it was mild.