New hepatitis B infections are most common among adults aged 30–49 years old, owing to the fact that many people in this age range have not been vaccinated as advised. Children under five are also at risk because they can't tell the difference between a healthy liver and one with chronic hepatitis B. The virus that causes hepatitis B can also cause serious long-term problems for those who are infected. Infection during adulthood may lead to cirrhosis of the liver, cancer, or death. People who are infected while still babies usually will grow up to be sickly if they are not given the proper treatment immediately after diagnosis. The only cure for hepatitis B is a replacement liver transplant or therapy which restores the patient's immune system to fight off the infection. Hepatitis C is more likely to cause severe disease in infants born to mothers with hepatitis B or C than it is in adults. This is because their immune systems are not developed enough to fight off the virus that causes it. Most children born with hepatitis C do not know it until they are diagnosed with some other condition, such as diabetes or hemophilia. At that point, they need treatment before their organs begin to fail.