Provided is a method for producing an influenza HA split vaccine which produces an antibody that binds to a HA stem region of influenza, the HA stem region being less likely to cause antigenic variation, An influenza HA split vaccine is subjected to an acidic treatment. Through the acidic treatment, an influenza HA split vaccine which produces an antibody that binds to a LAH of the HA stem region is obtained. This influenza HA split vaccine has an excellent protective ability against infection of other influenza viruses of different antigenicity.
