The hepatitis B vaccine is a recombinant vaccine. This means that yeast cells are used to duplicate a protein on the outer wall of the hepatitis B virus. This protein is filtered out of the solution and used in the vaccine. There is no way that someone can become infected with the virus because only the capsule protein is used as the immune-system stimulant. However, this process does make it more likely that someone with an allergy to yeast might have a reaction to the vaccine.
There are many different schedules for the hepatitis B vaccine. One common schedule is to give the first dose at birth, the second one month later, and the third dose six months after the first dose. This is also an acceptable schedule for adults. Another common schedule is to give the three doses at birth, two, and six months of age.
One important detail is that children who are born to mothers who are hepatitis B carriers need to get the vaccine within twelve hours of birth. At the same time, they will receive a dose of hepatitis B immune globulin (HBIG), which contains antibodies against the virus. This combination of vaccine and HBIG dramatically decreases the risk that the baby will contract hepatitis B from its mother.