All babies born from Tuesday in England, Wales and Northern Ireland will have an anti-hepatitis B injection added to the other routine vaccinations they are given in their early life.
The jab protects against viral infections that cause cirrhosis and liver cancer.
Babies are already vaccinated against diphtheria, tetanus, whooping cough, Hib and polio.
Public Health England said the new vaccine had been “shown to be safe”.
Babies are currently given vaccinations when they are eight, 12 and 16 weeks old and the new injection will be given at the same time as the others.
Previously, the hepatitis B vaccine was available on the NHS as a separate jab and was only administered to infants considered at risk, such as those born to infected mothers.
While hepatitis B rates in the UK are generally very low, in some inner city areas up to 1% of antenatal women are infected.
The infection has no symptoms so many of these women will be unaware they are ill, while their babies are considered at high risk.
Mary Ramsay, head of immunisation at Public Health England, said: “The Hexavalent vaccine has been extensively tested and shown to be safe and is widely used internationally with millions of doses being given around the world.”
The six-in-one vaccine does not have any live organisms, meaning there is no risk of infants contracting any of the diseases.
Health Protection Scotland has previously indicated it will adopt a similar policy.