A California city with a large number of whooping cough cases despite a high immunization rate is revealing the limitations of the current vaccine used to protect against the disease, a newspaper reported.



Elk Grove had a whooping-cough infection rate three to five times higher than other places in Sacramento County last year even though only 80 of the suburb's 4,500 kindergartners opted out of vaccinations, according to the Sacramento Bee.



"Children who were vaccinated did not receive the protection desired,'' said Kate McAuley, program coordinator of communicable disease and immunization at the Sacramento County Public Health Department.



Experts say the whooping cough vaccine introduced in the late 1990s provides less protection each year after it is administered, often leaving children vulnerable before they get their booster shot, the Bee reported.

The new vaccine uses only pieces of the bacteria that cause whooping cough, or pertussis, as opposed to whole, dead bacteria. The change was made after some children who took the earlier vaccine experienced reactions including a high fever and seizures.

But the new vaccine loses its effectiveness after its first year, according to experts and a recent study in the Journal of the American Medical Association.



Concerns about the vaccine come as a record-high 11,000 Californians caught whooping cough in 2014 and a measles outbreak sweeps the state. Parents of unvaccinated children have been blamed for the measles outbreak, but experts say pertussis is different.



"It's not correct to only pin (the pertussis outbreak) on the people who are unvaccinated,'' Mark Sawyer, a professor of pediatrics at the University of California, San Diego, and a member of the U.S. Centers for Disease Control and Prevention's immunization practices committee, told the Bee. "The effectiveness of the vaccine is a huge part of this. People who are immunized do still get pertussis.''



Still, Sawyer and other experts said parents should vaccinate their children against whooping cough because the vaccine reduces the chances of infection. Pertussis — symptoms of which include fever, vomiting, fatigue and a severe cough that forces people to take deep breaths that result in a "whooping'' sound — can be fatal.



And they encourage adults to get a pertussis booster shot if it has been more than a decade since their last shot, or they spend time around infants.



"People shouldn't avoid this vaccine for any reason,'' Sawyer said.