Audio A KPBS investigation has found that nearly two out of three people diagnosed with whooping cough in San Diego County this year were fully immunized. California is in the midst of the worst whooping cough epidemic in 50 years. The numbers raise questions about how well the vaccine works.



 A KPBS investigation has found that nearly two out of three people diagnosed with whooping cough in San Diego County this year were fully immunized. California is in the midst of the worst whooping cough epidemic in 50 years.

The numbers raise questions about how well the vaccine works.

Whooping cough, or pertussis is a contagious upper respiratory illness that in adults can mimic a bad cold. But in babies it can be deadly. Eight babies have died in California from whooping cough since January.

KPBS examined data from San Diego County’s Health and Human Services Agency from this year so far. We found that of 332 confirmed cases of whooping cough, 197 of the people who got sick were up to date with their immunizations. (Story continues below)

CDC Statement On Why Vaccinated People In Calif. Are Contracting Pertussis Vaccines for pertussis are very effective, but no vaccine protects forever in 100 percent of those vaccinated. Protection wanes over time, which is the reason for intermittent “booster doses.” High vaccination coverage in communities and in families also protects others, including those who are too young to be vaccinated or whose immunity from vaccination has waned. CA is experiencing a significant increase in pertussis circulating in the community. That disease pressure is causing more fully vaccinated and recently vaccinated people to become infected than in a typical year. It does not mean the vaccine is not working. Rather, the higher the vaccine coverage, the higher the proportion of cases who have been vaccinated. This is commonly misinterpreted to mean that a vaccine is not working, when in fact it means that coverage is high.

“I was a little surprised that there was as high a number of fully vaccinated people who got pertussis,” says Dr. Dean Sidelinger, the county’s deputy public health officer.

Sidelinger says 29 of those cases involved babies under six months of age who were immunized, but too young to have full protection against the disease. He is also skepitcal about making assumptions based on the statistics.

“I wouldn’t put all my faith into this I’m sure there is probably more protection from the vaccine then these numbers bear out, but it does show not every vaccine works 100 percent of the time.”

Just how much protection the vaccine provides is up for debate among researchers.

“The studies have a range of effectiveness but most of them fall 80 – 90 percent effective,” says Tom Clark, a scientist with the Centers for Disease Control in Atlanta.

“That’s wrong,” according to Dr. James Cherry, a professor with UCLA, referring to Clark's statement. Cherry has been studying whooping cough for 30 years.

“Vaccine efficacy is not an absolute measure,” says Dr. Fritz Mooi, a scientist with the Netherlands Center for Infectious Disease Control.

Mooi says he can’t put a number on vaccine efficacy.

All three researchers are world authorities with different views on how well the vaccine works. And whether it’s contributing to one of the largest pertussis outbreaks in California – and in other outbreaks around the world.

Mooi says there have also been examples of vaccinated children developing whooping cough in Ireland.

“I think we are seeing that everywhere where vaccinated children whom you would not expect to see get infected, get infected nevertheless.”

Mooi says the vaccine was developed for an older strain of whooping cough. He says the newer strain makes more toxins and puts increased pressure on our immune system. That can lead to illness despite immunization.

“Fritz Mooi is a brilliant scientist but when he tries to put epidemiology with it he screws up." Cherry says referring to Mooi's theory.

Cherry believes current vaccines aren’t as good as the ones used prior to the mid-nineties, but they’re safer and have fewer side effects.

“We gave up something for decreased reactions: we gave up efficacy.”

Cherry says ideally we need new vaccines, but the current vaccines – if used more frequently – especially in older kids and adults, could prevent the spread of whooping cough.

Several sources, including the official Journal of American Pediatrics, show Dr. Cherry received speaking fees and research funds from pharmaceutical companies which produce the pertussis vaccine.

“I think we have to be honest and try to find out what’s happening.” Mooi says.

Mooi believes researchers need to develop new vaccines. But he says the idea that the disease may be mutating and out-smarting current vaccines has been ignored by many public health officials

“That’s not good science and that’s not good public health.”

When KPBS asked the CDC why it believed so many vaccinated people in San Diego county contracted whooping cough - nearly two out of three people - the agency provided a written statement. The CDC says statistically, higher vaccination rates increases the probability a sick person will have been immunized.

The CDC says the data do not indicate the vaccine is ineffective.

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