Very-low-dose hepatitis B vaccine in newborn infants: an economic option for control in endemic areas.

Three 1 microgram or 2 micrograms doses of Merck, Sharp and Dohme plasma vaccine were given to 119 infants of mothers negative for antibody to hepatitis B surface antigen (anti-HBs). Anti-HBs antibodies developed in 25/29 (86%) infants given 1 microgram and in 86/90 (96%) given 2 micrograms doses. Levels of anti-HBs achieved by three 2 micrograms doses were similar to those that have been reported for conventional 10 micrograms doses. Similar levels were recorded from infants of anti-HBs-positive mothers, which suggests that maternal antibody does not interfere with the infant's immune response to low doses of vaccine. Three 2 micrograms doses of vaccine in infancy produce satisfactory immunogenicity and make possible economic control of hepatitis B in endemic areas.