Liz Szabo

USA TODAY

Vaccines given to infants and young children over the past two decades will prevent 322 million illnesses, 21 million hospitalizations and 732,000 deaths over the course of their lifetimes, according to a new report from the Centers for Disease Control and Prevention.

Vaccines also will have saved $295 billion in direct costs, such as medical expenses, and a total of more than $1.3 trillion in societal costs over that time, because children who were spared from sometimes-devastating illnesses will be able to contribute to society, the report shows. These calculations may underestimate the full impact of vaccines, the study notes, because authors considered only the early 14 routine childhood immunizations typically required for school entry. Authors didn't include flu shots or adolescent vaccines given at ages 11 or 12.

The CDC released the report at a time when many parents are uncertain about the benefits of vaccines, leading some to skip or delay routine childhood shots. Authors of the new report based their estimates on CDC annual immunization surveys and published reports showing the known efficacy of vaccines, as well as complication rates from infectious diseases.

Before the measles vaccine became available in 1963, the virus infected about 500,000 Americans a year, causing 500 deaths and 48,000 hospitalizations. In recent years, the number of diagnoses fell to around 60 to 65, mostly in isolated travelers arriving in the USA.

Doubts about vaccines safety – and fading memories of vaccine-preventable diseases — have contributed to a resurgence of nearly forgotten diseases such as measles, which was officially declared eradicated in the USA in 2000. Numerous studies have debunked the notion that vaccines cause autism or other chronic diseases, says William Schaffner, an infectious disease specialist and professor at the Vanderbilt University School of Medicine in Nashville.

"We have roomfuls of evidence" showing that vaccines are some of the safest medications available, Schaffner says, "but rumors and conspiracy theories still spread. Young parents today haven't seen these disease, and they don't respect and fear them."

The CDC reports that 129 people in the USA have developed measles this year, in 13 outbreaks largely sparked by unvaccinated travelers who become infected while abroad, then spread the disease to their communities. Most measles patients were either unvaccinated or didn't know whether they had been vaccinated. Among the unvaccinated measles cases, 68% had a "personal belief" exemption from school vaccination requirements, the CDC's Anne Schuchat says.

The USA also is fighting outbreaks of whooping cough, which has infected 5,634 people this year. Mumps has sickened 393 this year, more than twice the number of cases in 2013.

Health officials have battled such outbreaks for the past 20 years through the federal Vaccines for Children program, which provides free immunizations to poor and uninsured kids. About half of children and teens in the USA are eligible for the program, which has a budget of $4 billion a year, according to the CDC.

Congress created the entitlement program in 1994, responding to a measles outbreak in 1989 to 1991 that sickened 55,000 people and killed more than 100. At the time, measles outbreaks were fueled by viruses circulating among low-income, inner-city residents.

The picture has completely changed today, Schaffner says. The federal program has eliminated racial and ethnic disparities among vaccines. Today, the bulk of the unvaccinated children come from wealthy, educated families where parents intentionally choose not to immunize them, due to concerns about vaccine safety. These relatively wealthy children can then spread measles after returning from vacations in Europe, which has had large outbreaks for several years, Schaffner says.

"Borders can't stop measles, but vaccination can," CDC Director Tom Frieden says.

Containing a measles outbreak can be tricky, given that many younger doctors have never seen a case, says Julia Shaklee Sammons, a hospital epidemiologist at Children's Hospital of Philadelphia. That can allow measles to spread in doctor's offices and hospitals, Sammons wrote in an article in Annals of Internal Medicine published today.

Sammons described the typical symptoms and course of a measles infection in her article to help remind younger doctors who aren't familiar with the disease.

The CDC recommends two doses of the measles, mumps, and rubella vaccine for babies starting at age 12 months. Babies who will be traveling internationally can receive one dose as early as 6 months.

Adults who aren't sure if they've been vaccinated should also get a measles booster before going abroad, especially to the Phillippines, where an ongoing outbreak has sickened 20,000 people, Schuchat says.

"If you're not sure, get another dose," Schuchat says.