 14. The use of prophylactic medications e.g. acetaminophenparacetamol, aspirin, naproxen, or ibuprofen within 24 hours of randomization to prevent or pre-empt symptoms due to vaccination. Subjects discovered to have taken a prophylactic medication to prevent or pre empt symptoms due to vaccination within the 24 hours prior to planned randomization must be delayed until at least the 24-hour period is met; 