IF YOU WANT a lift in this holiday season, take a look at the annual report just issued by the United Nation's Children's Fund. In the poorest parts of the world, children die of simple things. Malnutrition, contaminated water and dehydration caused by uncontrolled diarrhea are major killers. So are the childhood diseases that used to be common here but have been all but eradicated: measles, tetanus, whooping cough, polio, diphtheria and tuberculosis.

James Grant, UNICEF's executive director who is an American, says that many of these problems can be attacked at relatively low cost. The return to breast feeding, as opposed to infant formulas, has cut down on water-borne infection. The use of simple rehydration packets -- a salt, sugar and water solution that costs about 10 cents apiece -- has saved the lives of half a million children this year and will save eight times that number as the procedure becomes more widely known. Simple growth charts distributed at the village level enable mothers to spot early signs of malnutrition and seek help.

UNICEF's priority for the remainder of this decade will be to innoculate all the world's children in fulfillment of a U.N. goal to achieve this objective by 1990. The vaccines are readily available at low cost, but new strategies are being developed to transport and administer them, to enlist the support of local governments and to educate and encourage mothers to take advantage of the service. Some vaccines can be freeze-dried to prolong their potency. "Cold chains" of refrigeration, based on kerosene, bottled gas, electricity, solar energy or ice boxes, have been set up in most nations. Hundreds of thousands of volunteers have been trained to administer vaccines, and governments have proclaimed highly organized immunization days that have been well advertised, promoted by churches and schools and available in even the most remote areas.

In Brazil, 20 million children are vaccinated every time a national immunization day is held. Two-thirds of Turkey's young children were vaccinated in eight days. The Indian government, as a living memorial to former Prime Minister Indira Gandhi, has raised immunization rates in Delhi from 20 percent to over 80 percent in a year. Americans can help by supporting U.S. aid programs and the work of international agencies such as UNICEF. Private groups make important contributions too. Rotary International, for example, has pledged to supply all the polio vaccine required in any developing country for the next five years, a gift that could cost $120 million.

This is exciting and invaluable work in which spectacular results are being achieved at low cost. The UNICEF report is good news for all who care about the world's poor children.