Wars, disease, even personal choice have left children around the world, in rich countries and in poor, underimmunized. The World Health Organization says progress toward global vaccination targets for this year are far off track.

"One out of five children is missed out of routine immunization," said the WHO's Dr. Jean-Marie Okwo-Bele, a public health expert.

In practical terms, this means that 1.5 million children will most likely die from preventable diseases, such as polio, measles and tetanus.

It wasn't until mid-April that immunization programs started up again in the Ebola-stricken countries of West Africa. The WHO said most of the children who are missing their immunizations live in the world's poorest countries.

But some live in rich countries like the United States. The U.S. weathered a measles outbreak that started at the Disneyland amusement park in California last December and lasted until mid-April. Measles can kill. It can also cause blindness, hearing loss and permanent brain damage.

Some parents, however, are lobbying for the right to decide whether to vaccinate. Many such parents are concerned that vaccines can cause autism, despite several studies that show it does not.

Yet another study disproving any connection between autism and a vaccine against measles and mumps has been published in the Journal of the American Medical Association. This study followed nearly 100,000 children who had been vaccinated up until the age of 5.

Dr. Anjali Jain of the Lewin Group, a health care consulting firm in Falls Church, Virginia, led the study. She said that "we found no evidence of a harmful association between the MMR vaccine and autism spectrum disorders."

On a positive note, the Americas are now free of rubella, a viral disease similar to measles. That's according to the Pan American Health Organization, which is part of the WHO.

The WHO aims to eliminate rubella from another region by the end of this year and redouble its efforts to make sure more children get the vaccinations they need to stay healthy and lead productive lives.