Table 1.

Description of adverse event grading in vaccine clinical trials.

Adverse Reaction Grade	General Descriptions
1	Mild. Does not interfere with normal activity
2	Moderate. Interference with normal activity. Little or no treatment required.
3	Severe. Prevents normal activity. Requires treatment.
4	Serious or Potentially Life-Threatening. Generally requires hospitalisation and stopping of any clinical trial where this grade is observed.