Health officials in the UK have urged millions of parents to vaccinate their children due to the rising number of measles cases in the country. The sharp increase in measles cases in the UK at a time when vaccination against measles, rubella and mumps, known as MMR, is at its lowest level. The mixed vaccine against the three diseases is offered free of charge in two doses. The first vaccine is recommended to be administered to babies before they turn one year old and the reminder vaccine when children reach the age of 3. Jenny Harries, Chief Executive of the UK Health Safety Agency, reported that vaccination rates have fallen to around 85 percent across the country, and much lower in parts of London. A 95 percent vaccination rate is recommended by the World Health Organization (WHO) to "maintain safe population coverage". Officials warn that outbreaks can occur wherever vaccination coverage is below the 95 percent needed to ensure herd immunity. In 2017, measles was declared eradicated in the UK, but cases have continued to rise since then. According to public health officials, more than 3.4 million children under the age of 16 are vulnerable and at risk of contracting the disease.