Article Source: University of Illinois at Chicago
Abstract: Vaccination in the period from 1963 to 2015 prevented nearly 200 million cases of polio, measles, mumps, rubella, varicella, adenovirus, rabies and hepatitis A and approximately 450,000 deaths from these diseases in the US alone, says new study.
Complete report: Researchers from University of Illinois have estimated that approximately 200 million cases of diseases like polio, measles, mumps, rubella, varicella, adenovirus, rabies and hepatitis A – and over 450,000 deaths from these diseases, were prevented in the U.S. alone between 1963 and 2015 by vaccination. The study has been published recently in AIMS Public Health.
In the year 1963, vaccination targeting these infections became widespread, the reason being the development of a human cell strain that allowed vaccines to be produced safely. On a global level, an estimate of 4.5 billion cases of diseases were prevented and over 10 million lives were saved due to the vaccines developed from this strain and its derivatives.
The study began when the coauthor Leonard Hayflick from the University of California, San Francisco approached the author S. Jay Olshansky, professor of epidemiology and biostatistics at the University of Illinois at Chicago School of Public Health as he wanted to know how many lives had been saved by his development of cell strain WI-38.
The normal human cell strain was developed by Hayflick in 1962 which has been in use ever since to safely grow the viruses which are required to produce vaccines against more than 10 diseases. Previously, many viral vaccines had been grown in monkey cells, but contamination with potentially dangerous monkey viruses forced an end to production, leaving millions vulnerable to common diseases.
In the context of the study, Hayflick says, “Given the acknowledged large, positive global health impact of vaccines in general, I was curious what contribution my discovery of WI-38 in 1962 had in saving lives and reducing morbidity, since a large number of viral vaccines in use today are made with my cell strain or its derivatives.”
So, for finding out the number of cases of disease and deaths prevented by vaccines developed using WI-38, Olshansky used previously-published data on cases and deaths for each disease in the U.S. in 1960, before vaccines were available for these diseases. He made an assumption that these prevalence rates would have held constant through the years without vaccines. Because vaccines for individual disease were introduced over time, to determine how many cases were prevented and lives saved for each disease, Olshansky multiplied the number of years the vaccine has been out (from its debut through 2015) by the prevalence of cases and deaths caused by that disease in 1960.
“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. “The anti-vaccination movement endangers the health of an entire generation of children.”
Measles outbreaks in California in 2014 and 2015 among unvaccinated children are just one example of the resurgence of previously unseen diseases attributable to parents who wrongly believe that vaccines have been shown to be harmful.
“The reduced number of children being vaccinated in the U.S. isn’t just a problem for those children,” said Olshansky. “It’s a problem for the country because it lowers herd immunity.”
When enough people in a community are immunized against a particular disease, if an unimmunized person becomes infected, then it becomes more difficult for that disease to get passed on to few others who are unimmunized. This is termed as ‘herd immunity.’ But if most people refrain from taking the vaccination, outbreaks can occur as the disease spreads among unimmunized individuals.
Disease like measles and few other which were previously thought to have become dormant recently emerged in the U.S. which demonstrates that the anti-vaccination movement is having a direct, negative effect on public health, Olshansky said, and vaccination rates for measles, mumps and rubella (MMR) in the U.S. are now as low as 50 to 86 percent.
According to Olshansky,”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.” A 1998 study often cited by the anti-vaccine movement claimed a link between vaccines and autism in children, but that study has since been shown to be fraudulent.
Nearly 1.4 million children under 5 worldwide still die each year due to lack of access 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.
“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.”
J. Olshansky, L. Hayflick.The Role of the WI-38 Cell Strain in Saving Lives and Reducing Morbidity.AIMS Public Health, 2017; 4 (2): 127 DOI: 10.3934/publichealth.2017.2.127