Many vaccine viruses used to be made in monkey cells and would then be transferred to humans. But the risk of money-borne infections contaminating the intended virus made this process too risky.

So in 1963, a new method was developed that replaced monkey cells with human cells known as “cell strain WI-38,” an incubator that held none of the potential for extraneous infection.

This was a game-changer for public health, making vaccines far more available and unquestionably effective. Through 2015, WI-38 has saved more than 450,000 lives and prevented more than 200 million people from contracting dangerous diseases, according to a new study published in AIMS Public Health.

The diseases that were considered in the study are polio, measles, mumps, rubella, varicella, adenovirus, rabies, and hepatitis A, many of which ravage the human body.

Take Action: Vaccines Should Be Accessible and Affordable For All

More than 10 vaccines have been made using the WI-38 method, which was developed by the University of California researcher Leonard Hayflick. Last year, Hayflick collaborated with S. Jay Olshansky, professor of epidemiology and biostatistics at the University of Illinois at Chicago School of Public Health, to conduct the analysis of how many people have been saved.

Hayflick said that the rise of the anti-vaccine movement motivated him to further illustrate the effective of vaccines.

“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,” Hayflick said in a press release. “The anti-vaccination movement endangers the health of an entire generation of children.”

In recent years, parents across the US have refused to vaccinate their children, imperilling what is known as “herd immunity.” When enough people in a community or “herd” are vaccinated, then if a disease appears, it will have a hard time finding new vectors to instigate an outbreak. When more and more people forgo vaccinations, a disease has more potential vectors, and therefore more potential for an outbreak.

Read More: Vaccines Are So Clearly Effective, Even Congress Agrees They Are Safe

Outbreaks in recent years of measles and mumps have shown the risks of losing herd immunity.

Vaccination rates in the US for certain diseases like measles, mumps and rubella (MMR) are reaching dangerous lows — often as few as 50% to 86% in age groups are vaccinated.

Around the rest of the world, where vaccines may not be as readily available as in the US, 1.4 million children under the age of 5 are endangered through lack of vaccination.

Similar anti-vaxxer momentum elsewhere in the world would derail the progress that has been against polio, a catastrophic disease that is 99.99% eradicated thanks to vaccines.

“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,” Olshansky said in the press release.

Anti-vaxxers often believe that vaccines can cause autism or other neurological diseases, a claim that has been debunked countless times.

Read More: Japan Gives $33.3 Million to End Polio For Good

The election of US President Donald Trump makes some health advocates worried because he has doubted vaccines in the past. 

“If the anti-vaccination movement gains any additional traction, developed and developing nations will have taken a dangerous step backward in protecting public health, especially of children,” Hayflick said.

“There is no medication, lifestyle change, public health innovation, or medical procedure ever developed that has even come close to the life-saving, life-extending, and primary prevention benefits associated with vaccines.”


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Study: Vaccines Have Prevented 450,000 Deaths in US Since 1963

By Joe McCarthy