SAN DIEGO -- The Trudeau family is back to their normal routine after 7-year-old Effraim and 10-year-old Shanice came down with whooping cough, also known as pertussis.

“She would cough so hard she would literally throw up,“ mother Lyla Trudeau said.

The illness, now at epidemic levels in California, is highly contagious. The Trudeaus had to be quarantined for a week.

“The health department contacted us a couple of times to make sure where we’d been; who we had been around ... ,” Trudeau said.

Whooping cough is especially dangerous for babies: eight have died in California so far this year, including one from San Diego County.

“Our strategy is to get everybody immunized so we can protect young babies,” Dr. Mark Sawyer said.

Sawyer is a pediatric infectious disease specialist at Rady Children’s Hospital.

“Everybody up to age 64 should be getting one version or another of pertussis vaccine,” he said.

However, that push for vaccinations by health officials is coming up against a push back from some parents. There’s a growing trend in California of parents opting out of vaccines.

Our media partner, the Watchdog Institute, crunched the numbers for kindergartners entering California schools in 2009. The number entering kindergarten with so-called “personal belief exemptions” against vaccines hit 10,280 last year. That is nearly quadruple the number of exemptions in 1990.

“Parents who chose not to immunize their children are making that decision not only for themselves but they are really making that decision for all the children who are around them,” Sawyer said.

A study published in the Journal of the American Medical Association estimated that for every 1% increase in exemptions, the risk of a pertussis outbreak goes up 12%.

In San Diego County, private schools, public charter schools and public schools in affluent areas have the highest opt-out rates.

The private Waldorf School of San Diego had the most. Half of its kindergartners had exemptions for vaccines.

California Virtual Academy, San Diego, had exemptions for 45% of its kindergartners. Greater San Diego Academy, which caters to homeschoolers, had a 39% exemption rate.

Also high for exemptions was the San Diego Cooperative Charter School where an unvaccinated child led to a measles outbreak two years ago.

“I think all the preventable diseases will come back if we don’t continue to immunize,” Sawyer said.

Rebecca Estepp is the mother of an autistic child who had adverse vaccine reactions as a baby. “I’m not anti-vaccine, I am for informed choice,” she said.

Estepp said some families, like hers, have genetic sensitivities to vaccines that should not be ignored.

“Vaccination isn’t just a rite of passage. It’s something you have to think about, one size does not fit all,” she said.

Regarding the re-emergence of whooping cough, she pointed out that even the Centers for Disease Control acknowledge on their website that decreased vaccinations is only one of several factors. Other potential factors listed by the CDC as causes for more whooping cough cases are increased awareness, improved testing, sub-optimal vaccines and adaptations in the bacteria that cause pertussis.

“But that information is not getting out," Estepp said, "all we are hearing about is this is because families have decided not to vaccinate."

In fact, most confirmed cases of whooping cough have been in people who were vaccinated, like the Trudeau children. Both were up to date on their vaccines.

Dr. Sawyer said the vaccine has an 80% success rate. “Which is good, but it doesn’t prevent all infections,” he said.

Still, he said that vaccination is the most effective method the community has to keep the epidemic in check.

» Click Here To Find Out How Many Kindergartners Near You Opted Out Of Vaccines

Learn more about the Watchdog Institute and their work, visit watchdoginstitute.org.