The present invention is a Haemophilus parasuis vaccine against serovar type 4 capable of triggering a protective immune response when administered to pigs as a killed vaccine. The present invention is also a method for vaccinating swine against Haemophilus parasuis infection, serovar type 4, by a) clonally propagating one or more cells which are capable of triggering an immune response against Haemophilus parasuis infection, serovar type 4, that protects the pig against Haemophilus parasuis infection, and b) combining an immunologically effective amount of the cells with a veterinarily acceptable carrier in a form suitable for administration as a vaccine to the pig, and c) administering as a killed vaccine. The cell culture is from a pathogenic parent strain.