In the wake of several recent measles outbreaks, the U.S. Centers for Disease Control (CDC) have released a report that shows how crucial vaccinations are for saving children’s lives.

Immunizations will prevent more than 21 million hospitalizations and 732,000 deaths among children who were born in the last 20 years, according to the CDC report, which underscores the importance of sustaining high vaccination coverage.

Although the U.S. immunization program has been very successful, 129 cases of measles have been reported this year in the U.S., in 13 outbreaks. In 2013, 189 Americans had measles. The highest number of annual cases since 1996 was reported in 2011, when 220 cases were reported.

­­­­­­­­The Vaccines for Children program, which provides vaccines to children whose parents or caregivers can’t afford them, was launched in 1994, in direct response to a measles resurgence in the U.S. that resulted in tens of thousands of cases and more than a hundred deaths, despite the fact that a measles vaccine had been available since 1963.­­­­­­­­­­­­­­­­­­

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Measles is highly contagious, and it can spread quickly among people who are not vaccinated. The CDC recommend two doses of MMR (measles, mumps, and rubella) vaccine for children older than 12 months. Infants who are 6 through 11 months old should receive one dose of MMR vaccine before some international travel, according to the CDC.

Roberto Posada, MD, pediatric infectious disease specialist at The Mount Sinai Hospital in New York, told Healthline, “It is one of the most contagious viruses, and those infected can spread it even before getting sick. It can also cause life-threatening complications, such as infection of the brain or lungs.”

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According to the CDC, 34 people among the 129 cases this year were infected in other countries and brought measles home. Most of the remaining cases are known to be linked to importations. Most of the people who reported having measles in 2014 were not vaccinated or were unaware of their vaccination status.

Commenting on the CDC report, Posada said, “This report comes at a time when some cities, including New York and Los Angeles, are seeing the highest rates of measles in over a decade. Many of the current cases of measles are related to travelers bringing the disease from other countries where measles is more common, and then spreading it to others in the community.”

Posada advised parents to protect their children by making sure their immunizations are up to date. He added, “Other vaccines are also available against many other deadly diseases and parents should follow the recommendations of their pediatrician.”

In a press release, CDC director Tom Frieden said, “Current outbreaks of measles in the U.S. serve as a reminder that these diseases are only a plane ride away. Borders can’t stop measles, but vaccination can.”

Noting that not all diseases that threaten U.S. borders can be prevented today by vaccines, Frieden said different strategies to protect Americans are required. “The health security of the U.S. is only as strong as the health security of all nations around the world. We are all connected by the food we eat, the water we drink, and air we breathe,” he said.

Frieden advised that stopping outbreaks where they start is the most effective and least costly way to prevent disease and save lives at home and abroad.

The CDC’s analysis also found that hospitalizations avoided and lives saved through vaccination will save nearly $295 billion in direct costs and $1.38 trillion in total societal costs.