Record Number Of Whooping Cough Cases In San Diego County Despite Immunization

San Diego County is experiencing its highest number of whooping cough cases on record, and most of the people who have gotten sick were immunized, the county’s public health officer said.

So far this year, 1,855 positive cases have been recorded, with more than 80 percent of the people up to date on their whooping cough shots.

In a series of investigative articles in 2010, inewsource and KPBS first revealed a high rate of vaccine failure. Researchers now agree the whooping cough vaccine used today is not as effective as the vaccine used almost 20 years ago.

The older vaccine, made of whole bacterial cells killed in labs, had side effects, including seizures and prolonged crying spells in babies.

“There were complications associated and that was why there was movement to the current acellular vaccinations,” said Dr. Wilma Wooten, San Diego County’s public health officer.

In 1996, the U.S. Food and Drug Administration approved the new acellular vaccine, which uses only purified components of the disease-causing organism. It is considered safer than the whole-cell vaccine and is the only one used in the U.S. today.

Research is also being conducted into whether a change in the bacterium that causes whooping cough, also known as pertussis, is mutating and becoming resistant to the vaccine.

Dr. James Cherry is a physician and researcher at UCLA and a prominent expert in pertussis. Cherry believes the biggest reason we are seeing more cases of whooping cough is because of increased awareness and better testing.

“Basically, people are finding more cases,” he said.

Hardest hit by the latest outbreak have been children between 10 and 18, accounting for more than half of all cases in the county.

Whooping cough is highly contagious and may mimic a cold for the first 10 days. It can produce a violent and persistent cough with a unique “whooping” sound.

For infants, the disease can be deadly because they can’t cough up the mucus that collects in their lungs.

The epidemic extends across California, with 9,935 cases reported so far this year. For example, Sonoma County’s rate of the disease is 141 per 100,000 population, nearly as high as pre-vaccine rates in the 1940s.

At that time, before widespread vaccination, the rate of disease was around 157 cases per 100,000 population. By the 1970s, the pertussis infection rate had dropped to less than one per 100,000.

In the midst of the 2010 epidemic, the California Legislature passed a law mandating a sixth dose of the vaccine for everyone entering seventh grade. Research shows immunity to the disease wanes over time, and so adding a booster shot, called Tdap, was supposed to help curb the spread of the disease. Tdap protects against tetanus, diphtheria and pertussis.

Wooten said it’s too soon to know whether adding that extra shot will reduce the number of whooping cough cases in the future.

San Diego County