How effective is the varicella vaccine in preventing varicella disease?
Pre-licensure studies of varicella vaccine showed the vaccine to be 70-90% effective in preventing disease and more than 95% effective in protecting against severe disease. If a vaccinated person does get varicella, it is usually a very mild case with fewer lesions (usually <50, which are frequently not vesicular), mild or no fever, and a quicker recovery. Investigations of vaccine field effectiveness since vaccine licensure have demonstrated that vaccine provides 100% protection against moderate to severe disease and most commonly is effective in preventing 80-90% of all disease. These data indicate that the vaccine performs well under conditions of community use.
