Immunogenicity and Safety of a Chemically Synthesized Divalent Group A Streptococcal Vaccine

Table 1

Bactericidal activity of antisera to the divalent vaccine.

Serotype	CFU		Percentage reduction
	Immunized sera	Control sera
M1	69	>1000	93.1
M12	105	>1000	89.5

CFU of one plate more than 1000 were counted as 1000. Percent reduction in CFU = (1 − (mean CFU from immunized sera/mean CFU from control sera)) × 100. Indirect bactericidal assays were performed by adding 50 μL of M1 or M12 GAS to 50 μL of immunized sera or control sera. Then, 400 of μL nonopsonic heparinized human donor blood was added. The mixture was kept shaking for 3 h at room temperature, and then 50 μL of mixture was plated on blood agar. CFU was quantitated after incubating overnight.