To the Editor.
—A Medical News & Perspectives article entitled "Changes Ahead in Childhood Immunization"1 mentioned an investigational hepatitis A vaccine manufactured by Merck and Co (Vaqta). In the article, a Merck spokesperson stated that he hopes this vaccine will "translate into a safety advantage" compared with the currently licensed inactivated hepatitis A vaccine (Havrix, SmithKline Beecham Biologicals, Rixensart, Belgium).Havrix appears to be an extraordinarily safe vaccine. In the efficacy trial by Innis et al,2 more than 104 000 doses of Havrix were administered to children and adolescents without the occurrence of a single serious adverse event related to the vaccine.2 This safety record has been confirmed in clinical trials elsewhere.3To date, Havrix is the only licensed vaccine in the United States for the prevention of hepatitis A. No trials have been published comparing the safety of Havrix with that of Vaqta. Given the