Vaccines research. Undated file photo of a nurse with a syringe. Scientists have found immune cells can fight different strains of the same virus - a discovery which could help transform vaccine development. Issue date: Tuesday May 1, 2018. Vaccines become ineffective when a virus mutates, and tackling this problem is a priority for researchers. See PA story SCIENCE Vaccines. Photo credit should read: David Cheskin/PA Wire URN:36271912