Study published in The Lancet, Volume 349, Issue 9052, Pages 599 - 603, 1 March 1997.

The authors found, "There was a significant linear trend on all outcome measures, showing increasing pain scores from uncircumcised infants, to those circumcised with Emla, to those circumcised with placebo." Their interpretation was, "Circumcised infants showed a stronger pain response to subsequent routine vaccination than uncircumcised infants."

The full text is available on The Lancet site and at the CIRP library.
 

See also:

• Effect of neonatal circumcision on pain responses during vaccination in boys