Author: Paul T Francis
Position: Associate Professor, Community Medicine
Institution: Amrita Institute of Medical Sciences, Cochin, India
E-mail: paultfrancis@gmail.com
Additional Authors: Nil
Submitted Date: December 13, 2007
Published Date: December 13, 2007
This comment was originally posted as a “Reader Response” on the publication date indicated above. All Reader Responses are now available as comments.

I read with interest the study on Oral Cholera Vaccine.
But the main conclusions of the study seems to be unbelievable.

Herd protection/Herd effect prevents disease in some of the unimmunised because of being 'surrounded' by immune persons who probably prevent spread of disease agent. This makes the actual protection in the community a shade more than what we expect from the vaccine efficacy.

However the conclusions from this study is unbelievable. A vaccine whose efficacy is moderate (about 70%) when given to 50% of the population reducing the disease in the unvaccinated by 89% seems to defy all immunology and epidemiology.

Even though it is a 'model' study I feel that this incredible phenomenon requires some explanation within what is known about Cholera epidemiology and immunology.