Deaths from measles worldwide fell by almost half over a period of six years, World Health Organization and UNICEF said Friday.

The number of deaths fell to 454,000 in 2004 from 871,000 in 1999, thanks to an immunization campaign the UN called "an outstanding public health success story."

"If progress continues at this rate, the global goal to cut measles deaths by half (between 1999 and 2005) will have been achieved in time," said WHO Director-General Lee Jong-wook.

Face of child with measles. (Courtesy: CDC/Barbara Rice)

Sub-Saharan Africa experienced the largest reduction of cases and deaths, but the agencies noted progress has been slower in South Asia.

A safe and cheap measles vaccine has been available for measles, a highly contagious virus, since the 1960s.

Children under five are hardest hit by measles, which can lead to complications such as pneumonia, diarrhea, encephalitis, blindness and brain damage.

Donors such as the United States, Japan, Britain, Canada and Norway and international agencies raised more than $150 million US since 2001 to make measles vaccines available in poor countries, the UN said.