Hepatitis B is found in blood, semen and vaginal fluids, so your risk is above average if you’ve had unprotected sex with multiple partners, if you’ve ever injected drugs or if you’ve shared toothbrushes, razors or nail clippers with an infected person.
If you contract hepatitis B as an adult, there’s a 95 per cent chance your immune system will defeat it without medical treatment. However, children—most often infected during delivery—typically become lifelong carriers. This strain doesn’t necessarily show symptoms until it leads to complications, which are a risk for a quarter of chronic carriers. Therefore, most national health authorities suggest that children get the vaccine, along with at-risk adults who missed it in childhood.