The following groups of people shouldn't be vaccinated unless the risk of contracting the disease exceeds the small risk associated with the vaccine:
• Infants under six months, because of the risk of viral encephalitis.
• Pregnant women, because of a theoretical risk that the vaccine may infect the foetus.
• People with an egg allergy, as the vaccine is grown in eggs.
• People with compromised immune systems, such as those with HIV/Aids.
If you fall into one of these groups, ask your doctor for advice before being vaccinated.