It's a sentence no mother wants to hear when her child's health is at stake: "Sorry, we've run out of vaccines."
But it's a bleak reality many families in the developing world face.
In the video above produced by UNICEF, the humanitarian group points out that roughly one out of every five children around the world lacks access to vaccinations. This "immunization gap" is evident in the fictional narrative played out in the video, which follows two South African mothers with their young ones.
One of the babies -- whose mother lives in a nice neighborhood, has enough money to drive her own vehicle and visits a private doctor -- is able to get vaccinated. The other -- whose mother has no personal mode of transportation and is forced to wait in an overcrowded clinic to access medical attention for her child -- is denied the potentially lifesaving care because there were no vaccines left.
"Two mothers, two children, two very different journeys for vaccines," UNICEF says of the video.
Although UNICEF highlights the need for more children to gain access to vaccines, the world has made substantial progress in recent decades.
In an infographic provided to The Huffington Post in recognition of World Immunization Week last month, UNICEF points out that global coverage of DTP3 -- vaccinations protecting against diphtheria, pertussis (whooping cough) and tetanus -- has increased remarkably. In 1980, just 20 percent of children around the world were given the routine vaccinations -- in 2012, that figure had grown to 83 percent.
"Congratulations are due to many individuals and institutions for making all this happen," Flavia Bustreo, World Health Organization's assistant director-general for family, women's and children's health, wrote in a HuffPost blog in April of the globe's progress.
But as Bustreo noted, more needs to be done, as "progress towards global vaccination targets for 2015 is far off-track," WHO explains on its website. The group says that 1.5 million deaths could be averted each year if every child had access to vaccines.