Around 4,500 children in the county are not fully vaccinated against measles, according to Powys Teaching Health Board.
There have been 66 cases reported in Powys in the current outbreak, which the health board says is the third biggest outbreak in England and Wales since records began.
We need to vaccinate as many children as possible, but we need parents’ permission to do so.
If you receive a letter inviting your child to be vaccinated, please, please sign and return the consent form so that we can help to protect your child against measles.
2013 is expected to be the worst year for measles in the UK for the past two decades. Read more about the illness and how it is treated.
If the Government's top adviser on immunisation thinks the risk of an emergency in England is a possibility, I believe him.