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Whooping cough vaccine becomes less effective over time, study says

The modern vaccine for whooping cough becomes less effective as children age, a new study shows, highlighting the need for new vaccines to protect children f...

Posted: Jun 10, 2019 8:59 AM

The modern vaccine for whooping cough becomes less effective as children age, a new study shows, highlighting the need for new vaccines to protect children from the highly contagious disease.

Infants and children are supposed to receive five doses of the DTaP vaccine before age 7. Four vaccines are administered before 18 months, and another is given when a child is 4 to 6 years old. A similar booster shot is given when a child is 11 or 12 years old.

But the new research, published Monday in the journal Pediatrics, found that the risk of contracting whooping cough increased as children were further away from their last shot of the vaccine, suggesting that immunity wanes as time passes between doses.

Take, for example, a 5-year-old child who hasn't yet gotten their fifth dose. That child, who received their last shot more than three years ago, would be five times more likely to contract whooping cough than one who just received a dose within the past year, the study found.

The DTaP vaccine, which also protects against diphtheria and tetanus, was still found to be effective: The risk of coming down with whooping cough was 13 times higher in those who were unvaccinated, and almost twice as high in those who received some, but not all, of their shots.

"The bigger picture is that we've had several outbreaks of pertussis here in California over the past 9 years," said Dr. Nicola Klein, a co-author of the study and director of the Kaiser Permanente Vaccine Study Center. She emphasized that the vaccine generally works, but noted that "most of the children who had pertussis in our outbreaks were fully vaccinated."

Conducted by scientists at the Vaccine Study Center, the research looked at nearly half a million children born between 1999 and 2016, and found that most whooping cough cases -- 82% -- occurred in children who were fully vaccinated or over-vaccinated.

Those results, the researchers wrote, suggest that "suboptimal vaccine effectiveness played a major role in recent pertussis epidemics." Over 13,000 people contracted the disease in 2018, according to the CDC's most recent provisional report, and ten people died, four of whom were less than a year old.

Whooping cough, a respiratory disease caused by a type of bacteria called B. pertussis, can lead to violent and uncontrollable coughing that makes it hard to breathe, according to the CDC. It is particularly dangerous in young babies, for whom it can be deadly.

A safer, but perhaps less effective, vaccine

Before 1997, the whooping cough vaccine used actual cells of B. pertussis to trigger the immune system. Those cells had been inactivated, meaning they couldn't cause disease. But to combat side effects associated with these "whole-cell" vaccines, the CDC recommended in 1997 that a different type of shot be used: DTaP.

The new vaccines reduced side effects such as fever-associated seizures. The vaccines were created with little bits of the bacteria -- called antigens -- instead of entire cells.

Research has shown these new vaccines to be effective at preventing whooping cough, but a growing body of evidence suggests that protection decreases over time. One meta-analysis, for example, found that the odds of pertussis increased by 33% every additional year after the third or fifth dose of the vaccine.

"There is global recognition that the whole-cell vaccine has longer-lasting protection than the acellular vaccine," said Klein, referring to the older version of the vaccine used in some developing countries.

Still, that doesn't mean that the United States should go back to using it, Klein said. "I think probably what's more likely to be acceptable to countries that are currently using (newer) vaccines is some sort of version that incorporates some of the benefits of the whole-cell vaccine with less of the side effects," she said.

Dr. Kathryn Edwards, a professor of pediatrics at Vanderbilt University who was not involved in the study, wrote in an editorial that health care organizations and the CDC must "continue to monitor the pertussis burden in the United States and work with scientists to improve the existing pertussis vaccines."

That research is ongoing, Edwards noted. One technique currently being studied involves increasing the number of antigens -- the bits of B. pertussis cells that are recognized by the immune system -- to better mimic the older whole-cell vaccines.

Another option uses living, but weakened, bacteria that are injected into the nose.

Indiana Coronavirus Cases

Data is updated nightly.

Cases: 752108

Reported Deaths: 13816
CountyCasesDeaths
Marion1033831790
Lake558431013
Allen41736693
St. Joseph37007565
Hamilton36617417
Elkhart29425461
Tippecanoe22938228
Vanderburgh22565400
Porter19369327
Johnson18486389
Hendricks17696317
Clark13233195
Madison13176344
Vigo12631253
LaPorte12429221
Monroe12226176
Delaware10970198
Howard10349224
Kosciusko9643121
Hancock8578147
Bartholomew8174157
Warrick7864156
Floyd7815180
Grant7248179
Wayne7164201
Boone6979103
Morgan6768141
Dubois6224118
Marshall6214116
Cass6024110
Henry5903110
Dearborn589878
Noble581688
Jackson509476
Shelby502396
Lawrence4753122
Gibson445595
Clinton443555
Harrison441775
DeKalb440385
Montgomery439890
Whitley406744
Huntington403381
Steuben400859
Miami395769
Jasper389155
Knox377691
Putnam373461
Wabash362383
Ripley347370
Adams345555
Jefferson336186
White332753
Daviess3035100
Wells295481
Decatur289892
Greene286885
Fayette284864
Posey274335
LaGrange273272
Scott270356
Clay267148
Washington246336
Randolph245183
Jennings235349
Spencer234531
Starke228159
Fountain222048
Sullivan214843
Owen212358
Fulton204043
Jay201032
Carroll193820
Orange188255
Perry187237
Rush175926
Vermillion175344
Franklin170435
Tipton166646
Parke149616
Pike138334
Blackford136232
Pulaski120847
Newton114936
Brown104443
Benton102614
Crawford102516
Martin91815
Warren84115
Switzerland8158
Union72810
Ohio57911
Unassigned0424

Ohio Coronavirus Cases

Data is updated nightly.

Cases: 1109697

Reported Deaths: 20213
CountyCasesDeaths
Franklin1289521469
Cuyahoga1158802216
Hamilton814201251
Montgomery525861049
Summit484551006
Lucas43384824
Butler39098606
Stark33355930
Lorain25689506
Warren24612305
Mahoning22388602
Lake21219389
Clermont20138253
Delaware18892136
Licking16671225
Fairfield16589204
Trumbull16560483
Medina15618273
Greene15292248
Clark14244306
Wood13296200
Portage13254216
Allen11919239
Richland11611211
Miami10857225
Wayne9153225
Columbiana9039230
Muskingum8909135
Pickaway8664122
Tuscarawas8654251
Marion8649139
Erie8058165
Ashtabula7171179
Hancock6999133
Ross6948163
Geauga6850151
Scioto6540106
Belmont6159174
Union585049
Lawrence5741102
Jefferson5683159
Huron5554122
Sandusky5444126
Darke5420129
Seneca5350128
Washington5321109
Athens524460
Auglaize502487
Mercer487785
Shelby477095
Knox4573112
Madison444566
Ashland435997
Putnam4336104
Defiance432399
Fulton432274
Crawford4046110
Brown402761
Logan387678
Preble3859105
Clinton379266
Ottawa373581
Highland360266
Williams348578
Champaign344959
Guernsey325254
Jackson318454
Perry297350
Morrow291940
Fayette285750
Hardin275765
Henry273867
Holmes2703101
Coshocton269360
Van Wert247264
Adams243156
Pike242835
Gallia240850
Wyandot234756
Hocking220663
Carroll197548
Paulding176642
Meigs148540
Monroe136345
Noble136239
Harrison114138
Morgan110124
Vinton85717
Unassigned03
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