The next generation of Covid-19 vaccines in development could come as a pill or a nasal spray and be easier to store and transport than the current handful of shots that form the backbone of the world-wide vaccination effort. These newer vaccines, from U.S. government labs and companies including Sanofi SA, Altimmune Inc. and Gritstone Oncology Inc., also have the potential to provide longer-lasting immune responses and be more potent against newer and multiple viral variants, possibly helping to head off future pandemics, the companies say.