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San Diego’s Collective Immunity Threatened By Declining Vaccination Rates

San Diego’s Collective Immunity Threatened By Declining Vaccination Rates

When Daniela Mejia’s daughter Julieta was born, the first-time mother was wary of vaccines.

San Diego’s Collective Immunity Threatened By Declining Vaccination Rates


Joe Yeradi, reporter, iNewsource

Dr. Ellen Rodarte, Sharp Rees-Stealy Medical Centers


When Daniela Mejia’s daughter, Julieta, was born, the first-time mother was wary of vaccines.

"I wouldn't want to have my daughter suffer from any side effects of such a sudden invasion of infectious disease that was just given to her, you know?,” Mejia said. “I'd like her to be exposed slowly to bacterias and viruses and just naturally."

Because of her mother’s concerns, Julieta, now almost four, is one of thousands of young children in San Diego County who aren’t up to date on their vaccinations.

More than 3,300 kindergarteners -- in both public and private schools -- began the 2014-15 school year lacking one or more recommended vaccinations against diseases such as measles, polio and whooping cough, according to an inewsource analysis of data from the California Department of Public Health and the California Department of Education.

That’s nearly 8 percent of the county’s kindergarten population.

Interactive: Map Of Kindergarten Vaccination Rates In San Diego County

And while that represents a decline from the 2013-14 school year’s rate of almost 10 percent, it’s still an increase from a decade ago when the rate was less than six percent.

Immunologists are raising the alarm about what they say is our collective amnesia over the damage these diseases have wrought in the past.

Dr. Shane Crotty, a professor at the La Jolla Institute for Allergy and Immunology, said a parent’s decision to vaccinate their child is motivated by fear.

“It really comes down to two fears,” he said, “the fear of something happening if you get vaccinated versus the fear of something happening if you don’t get vaccinated.”

As decades of widespread vaccination eliminated once-feared diseases from the collective conscience of American parents, the first fear took preeminence in the minds of some.

“You’re like ‘Well, yeah, OK. I won’t vaccinate because I have this small little fear [of vaccination complications] because on the other side you really have no fear of your kid getting measles or polio because you’ve never seen it,” Crotty said.

Mejia believes that vaccines do work and could be right for some children. But the holistic care practitioner and massage therapist said that once she researched their potential dangers, she decided the risks were too great.

“This is research that one has to do on their own, like 'What are my options?' instead of out of fear, doing what my doctor said,” Mejia said.

That fear of vaccines’ complications (greatly overwrought, say scientists and medical professionals) -- and the decisions it leads to -- threatens not just the children whose parents choose not to vaccinate, but other children as well.

Thinning The Herd

So called “herd immunity” is the theory that at some point, enough members of a given population or “herd” are vaccinated against a particular disease that even the unvaccinated are protected.

The precise level at which a group achieves herd immunity varies by disease. For polio, the number usually given is around 85 percent. For whooping cough (also known as pertussis), many doctors say 92 percent or higher is required.

Herds can be any group in which members come into physical contact with each other, from a kindergarten class to an entire county.

Dr. James Cherry, a pediatric infectious disease specialist at the UCLA Medical Center, said maintaining herd immunity is crucial for a community’s well-being.

Cherry used measles as an example. A current outbreak of that highly contagious disease is believed to have originated with a visitor to Disneyland who was not vaccinated. Cherry said measles requires a 95 percent immunization rate to maintain herd immunity.

“When the overall herd immunity drops below that number and down to something like 90 percent, then you’re in trouble because then you’re going to get sustained transmission,” Cherry said.

Database: Kindergartens' Vaccination Exemption Rates

Mejia doesn’t believe that her decision not to vaccinate her daughter can affect the well-being of children who are vaccinated.

Photo caption:

Photo credit: Katie Schoolov

Daniela Mejia, a mother, is shown explaining why her daughter is one of thousands of young children in San Diego County who aren’t up-to-date on their vaccinations.

“If they have the vaccine, doesn’t that mean that they will be able to fight it off?” Mejia asked.

Crotty said that’s a common belief among parents. It’s also wrong.

“If there are unvaccinated kids who are getting sick, that absolutely raises the risk of vaccinated people getting sick because the vaccines aren’t perfect,” Crotty said.

Many vaccines work perhaps 95 percent of the time, Crotty said.

And not every child can be vaccinated before they’re exposed to unvaccinated children.

As an example, Crotty points to whooping cough. Children can’t be fully vaccinated against whooping cough until they’re more than a year old. Those babies’ vulnerability increases when they come into contact with unvaccinated older children.

“Whooping cough kills babies,” Crotty said. “And you can’t vaccinate the babies.”

They rely on herd immunity.

“The way to protect babies under 12 months is to have everybody else vaccinated so you get the herd immunity,” Crotty said.

The same goes for children with autoimmune disorders who can’t get vaccinated no matter their parents’ preferences.

Personal Beliefs

The data of vaccination records for kindergarteners shows that personal belief exemptions -- the opt-out parents can sign against immunizing their school children -- tend to be utilized by higher-income and presumptively better-educated parents.

A recent study found that as the percentage of people with graduate degrees in a neighborhood increased, so too did that neighborhood’s percentage of under-vaccinated children.

This phenomenon seems to hold in San Diego County, where nearly half of all non up-to-date kindergarteners had a personal belief exemption.

In the 2014-15 school year, the personal belief exemption rate among kindergarteners attending public school was 3.3 percent. The rate among kindergarteners attending private school was 5.8 percent.

The difference was even more pronounced when comparing the socioeconomic profiles of public kindergartens.

Among kindergarteners attending public schools where more than half of the student population qualified for free or reduced-cost meals, the personal belief exemption rate was 1.6 percent. The rate among kindergarteners attending public schools, where half or less of the student population qualified for the benefit, was 5.5 percent.

Cherry, the UCLA infectious disease specialist, wasn’t surprised by inewsource’s findings.

“The whole middle aisles of Whole Foods Markets are selling crap,” Cherry said. “And these are the people who go there.”

Cherry noted that Hispanics, whose educational attainment has historically trailed that of white Americans, have the highest proportion of vaccinations against whooping cough of any major ethnic or racial group.

“Because you have a college degree doesn’t mean you understood epidemiology or you understood cause and effect,” Cherry said.

Mejia currently takes Julieta to daycare a couple times a month. She hopes to enroll her in pre-kindergarten next month.

It’s a “co-op” school where Mejia estimates up-to-date vaccination rates may be as low as 80 percent.

Said Mejia, “So, this is actually a school where more parents share my point of view.”

inewsource investigative assistant Madison Hopkins contributed to this report.

KPBS' Patty Lane, Peggy Pico and Maureen Cavanaugh contributed to the Midday and Evening Edition segments.


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