Drugmakers are crafting Covid-19 vaccines that would target more than one strain of the virus, hoping to strengthen the immunization campaign against the pathogen as it evolves.Researchers at Moderna Inc., Novavax Inc.
and the University of Oxford are designing the shots, known as multivalent vaccines, to protect not only against the form of the virus commonly circulating globally but also potentially contagious strains that have emerged or might in the future.The work belongs to a range of efforts vaccine makers and drug researchers are undertaking to get ahead of variants like the one identified in the United Kingdom, South Africa and Brazil.Research indicates some vaccines currently in use generate weaker immune responses against the.