As the coronavirus mutations spread across the world and assume more contagious forms, Pfizer and Moderna, the two mRNA technology vaccine-makers, have claimed that their vaccines can give protection from new virus strains. Dr Peter Chin-Hong, Infectious Disease Specialist and Professor at University of California, San Francisco, told NDTV, "There is a difference between a variant and a strain. A variant happens every two week and a strain usually takes years to occur."