Influenza viruses have a great capacity to mutate and change. Current flu vaccines are safe and effective, but they have to be updated annually to match the epidemic strains and occasionally there is a mismatch with the circulating virus strains. There is hence a great need for new vaccines that can induce broad protective immunity against as many variants of influenza A virus as possible. This goes for seasonal influenza viruses, but it especially holds true for new subtypes with pandemic potential.
A flu vaccine would certainly become more universal if it were to entice the immune system to make antibodies and T-cells against parts of the virus that are genetically conserved, thus against epitopes on the virus that are common in all influenza viruses. In other words, to induce broad protective and long-lasting immunity, an influenza vaccine should be directed to conserved viral proteins. One of the candidate antigens is the M2e protein, which would elicit cross-reactive antibodies. Another group of antigens are the antigens that induce virus-specific T cells, which could play a very important role in protective immunity and supplement the effect of virus-specific antibodies. Current research aims to bring together all these antigens and produce the most potent, up-to-date influenza vaccine.