Several factors can categorize a patient as high risk: - Age: Patients over 65 or very young infants. - Chronic Conditions: Diabetes, heart disease, hypertension, and chronic respiratory diseases. - Immune System: Compromised immune systems due to diseases like HIV/AIDS, or treatments like chemotherapy. - Pregnancy: Pregnant women, especially those with pre-existing conditions. - Lifestyle Factors: Smoking, obesity, and substance abuse.