Influenza Vaccine By Margot L Savoy, MD, MPH, Lewis Katz School of Medicine at Temple University Reviewed / Revised Oct 2022 View Patient Education Preparations Indications Contraindications and Precautions Dose and Administration Adverse Effects More Information Based on recommendations by the World Health Organization and the Centers for Disease Control and Prevention (CDC), vaccines for influenza are modified annually to include the most prevalent strains (usually 2 strains of influenza A and 1 or 2 strains of influenza B).