Nucleic acid, including DNA, immunization is used to generate a protective immune response in a host, including humans, to a serine-threonine kinase (STK) of a strain of Chlamydia. A non-replicating vector, including a plasmid vector, contains a nucleotide sequence encoding a STK or a fragment of the STK that generates antibodies that specifically react with STK and a promoter sequence operatively coupled to the first nucleotide sequence for expression of the STK in the host. The non-replicating vector may be formulated with a pharmaceutically-acceptable carrier for in vivo administration to the host.