Influenza vaccines are administered using solid biodegradable microneedles. The microneedles are fabricated from the influenza vaccine in combination with solid excipient(s) and, after penetrating the skin, they dissolve in situ and release the vaccine to the immune system. The influenza vaccine is (i) a purified influenza virus surface antigen vaccine, rather than a live vaccine or a whole-virus or split inactivated vaccine (ii) an influenza vaccine prepared from viruses grown in cell culture, not eggs, (iii) a monovalent influenza vaccine e.g. for immunising against a pandemic strain, (iv) a bivalent vaccine, (v) a tetravalent or >；4-valent vaccine, (vi) a mercury-free vaccine, or (vii) a gelatin-free vaccine.
