A greater share of L.A. County pertussis cases in recent years are among kids 5 to 14, raising questions about the waning efficacy of the current vaccine and sending experts scrambling to review the vaccination schedule.
The recent death of an infant in Riverside County from pertussis has renewed concerns about the disease, also known as whooping cough.
It’s usually thought of as something that mainly targets babies, but from 2010 to 2012, 5 to 14-year-olds made up nearly a third of pertussis cases in Los Angeles County, according to the county Department of Public Health.
It’s a concern because older kids and adults often bring the infection home to infants, who are too young for the vaccine.
Public health officials say this is raising questions about how many times kids should get a pertussis shot. The current vaccine went into widespread use in 1997. It has fewer side effects than the previous one. For more than a decade, kids were getting five separate shots between the ages of 2 months and 7 years.
But public health officials discovered that "the effects of the vaccine does not seem to last as long as we had hoped," said Jonathan Fielding, director of the L.A. County public health department. "There is a lot of work going on to understand why it is waning."
In 2011, the state legislature mandated another pertussis shot, a booster for all incoming 7th graders.
"This is just coming to the surface," said James Watt, chief of communicable disease control at the state Department of Public Health. "The previous vaccines did not confer lifetime immunity but did confer a better duration."
He said national health officials are reviewing the effectiveness of the vaccine and the recommended schedule of doses.
Pertussis is cyclical and peaks every three to five years, according to the Centers for Disease Control. Over the last three decades the peaks have grown larger. CDC officials attribute that to "increased awareness, improved diagnostic tests, better reporting, more circulation of the bacteria, and waning immunity."
Statewide the number of pertussis cases last year were higher than the year before but still lower than the peak in 2010. In Los Angeles County the number of cases has been dropping since the high four years ago. But the share of cases among older kids has remained the same.
Last year pertussis cases in L.A. County among children 1 through 18 years of age were up 22 percent and among those under 1 year old cases were up 9 percent, said Fielding.
In 2013 there were 183 cases of pertussis in L.A. County and more are still being investigated, according to the county health department. There were 154 cases in 2012. In 2011 there were 453 cases and in 2010, the peak year, there were 972 cases.
Statewide, there were 2,372 cases of pertussis reported in 2013, an increase over the prior year. Children seven to 16 years of age accounted for 62 percent of the cases with the peak age being 15, according to the California Department of Public Health.
Los Angeles County, the CDC, AARP, and other groups have ongoing campaigns encouraging grandparents to get a booster so they can safely be around their grandchildren.
Of the pertussis cases in Los Angeles County, 8 percent were individuals who had never been vaccinated. Experts say the number is not a significant factor in the spread of pertussis.
Parents who do opt out will now have to get a health practitioner to sign a form before their children can start school. Governor Jerry Brown signed the law in the fall and it went into effect this year.
Pertussis vaccinations are given at 2, 4 and 6 months, between 15-18 months and again at 4 through 6 years old. A booster Tdap is given to all preteens before they enter 7th grade. Experts also recommend a booster for pregnant women and anyone who interacts with young children.