Vaccination rates have fluctuated around the globe in the last 15 years. World Health Organization

Do vaccines still matter? A new report says vaccinations have saved millions of lives in the last 50 years, but with more public debate about the perceived health risks of immunizations, it's not clear that the trend will continue.

Based on information about how prevalent nine diseases — including polio, measles, mumps, rubella and hepatitis A, among others — were in the time before vaccines, a study published in AIMS Public Health estimates the number of cases prevented, and thus deaths averted, through vaccinations for those diseases between 1963 and 2015. It puts the number of prevented deaths at 10.3 million across the globe.

Of that avoided death toll, the majority can be attributed to Asia, with 6.2 million lives spared. Out of the rest, about 450,000 were in the U.S.; 1 million in Europe; 1.6 million in Africa; and 886,000 in Latin America and the Caribbean, according to the study.

Those numbers, while already considerable, are dwarfed by the number of infections simply prevented or treated, as not everyone who would have contracted the illnesses would have died, even if they became disabled. The study puts those prevented or treated cases at 4.5 billion around the world, with 198 million of them in the U.S.

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“Vaccination is a particularly important issue to think about now, given the rise of an anti-vaccine movement that has the potential to reverse the health gains achieved through one of the most powerful interventions in medical history,” co-author Leonard Hayflick, from the University of California, San Francisco, said in a statement from the University of Illinois at Chicago, both institutions that worked on the project. “The anti-vaccination movement endangers the health of an entire generation of children.”

In order for vaccines to be truly effective, a large majority of people need to be immunized, referred to as “herd immunity.” Typically, herd immunity is achieved when the percentage of vaccinated people reaches the upper 90s, and in addition to stopping the spread of infection, it helps protect people who are vulnerable to contracting the illnesses yet cannot be vaccinated for health reasons, or because they are not old enough to be immunized. But statistics show that vaccination levels have suffered as more people question the benefits of vaccines — debates that in most cases can be traced back to a study that falsely linked childhood vaccines to autism. That study has since been debunked and retracted and its author discredited, but the myth persists.

Reports have linked recent outbreaks of vaccine-preventable infections like measles to anti-vaccination sentiment.

“It is ironic that in the anti-vaccination community, the very people who are denying protection to their children by foregoing vaccination are healthy and alive today because they, and possibly their parents, were vaccinated,” author and Chicago epidemiology professor S. Jay Olshansky said.

The Centers for Disease Control and Prevention warn against this trend with a real-life cautionary tale: In Japan in the 1970s, people stopped vaccinating their children against whooping cough, officially called pertussis, and at its rock-bottom only 10 percent were immunized. Thousands became infected, with 41 dying, but the infections dropped when vaccinations picked up again.

“It is possible that the anti-vaccination movement has arisen among younger generations, in part, because they cannot bear witness to the tragedy of disfigurement, morbidity, and death caused by viral and bacterial diseases,” the AIMS Public Health study says. But “the diseases our ancestors feared so much have not gone away — they lay dormant.”

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