Most of the developed world and many countries in the developing world include it in their immunization programs often in combination with measles and rubella vaccine known as MMR. A formulation with the previous three and the varicella (chickenpox) vaccine known as MMRV is also available. As of 2005 110 countries provided the vaccine as part of their immunization programs. In areas where widespread vaccination is carried out it has resulted in a more than 90% decline in rates of disease. Almost half a billion doses of one variety of the vaccine has been given.