Table 4.

Previous GAS human challenge studies. CFU/mL: colony-forming units per millilitre.

Year	Strain	Dose (CFU/mL)	Number of participants	Number of not vaccinated	Clinical illness in nonvaccine group	Reference
1971	M1	4 × 106	50	25	52%	[94]
1973	M1	4 × 106	44	23	74%	[95]
1975	M3, M12	5 × 106	84	36	44%	[96]