Whooping Cough Vaccine Diminishes After 5th Dose
Protection against whooping cough (also called pertussis) waned
during the five years after the fifth dose of the combined diphtheria,
tetanus, acellular pertussis (DTaP) vaccine, according to researchers
from the Kaiser Permanente Vaccine Study Center. The fifth dose of DTaP
is routinely given to 4- to 6-year-old children prior to starting
kindergarten.
The study appears in the current online issue of the New England Journal of Medicine.
This is the first study to specifically focus on the large population
of highly vaccinated children who had exclusively received DTaP
vaccines since birth and for whom enough time had passed since their
fifth dose that DTaP vaccine waning could be measured, said the
researchers. They explained that the study period included a large
pertussis outbreak that occurred in California
during 2010. Researchers examined the relationship between time since
vaccination with the likelihood of a positive pertussis test in the
Kaiser Permanente Northern California population, which includes 3.3
million members in an integrated care system with electronic medical
records and a central laboratory.
Researchers compared 277 children, 4 to 12 years of age, who were
positive for pertussis with 3,318 children who were negative for
pertussis and separately with 6,086 matched controls. They assessed the
risk of pertussis in children from 2006 to 2011 in California
relative to the time since the fifth dose of DTaP and found that
protection from pertussis after the fifth dose of DTaP vaccine wanes
more than 40 percent each year. The amount of protection remaining after
five years depends heavily on the initial effectiveness of the fifth
dose of DTaP, according to Nicola Klein, MD, PhD, co-director of the Kaiser Permanente Vaccine Study Center and the lead author of the study.
If the initial effectiveness of the fifth dose of DTaP was 95
percent, the effectiveness of DTaP would decrease to 71 percent after
five years. Whereas if the initial effectiveness was 90 percent, it
would decline to 42 percent after five years, explained the researchers.
"The findings suggest that whooping cough control measures may need
to be reconsidered. Prevention of future outbreaks may be best achieved
by developing new pertussis–containing vaccines or reformulating current
vaccines to provide long-lasting immunity," said Klein.
"That said, the DTaP vaccine is effective and remains an important
tool for protection against whooping cough for children and the
communities in which they live, and following current CDC
recommendations remains important."
The CDC currently recommends five DTaP shots for children. The first
three shots are given at 2, 4, and 6 months of age. The fourth shot is
given at 15 through 18 months of age, and a fifth shot is given when a
child enters school, at 4 through 6 years of age.
The first pertussis vaccine was developed in the 1930s and was in
widespread use by the mid-1940s, when pertussis vaccine was combined
with diphtheria and tetanus toxoids to make the combination whole cell
pertussis vaccine DTP. In 1991, concerns about DTP safety led to the
development of the acellular pertussis DTaP vaccines that are associated
with fewer side effects. DTaP vaccines have completely replaced the
whole cell DTP vaccines in the United States as well as in many countries around the world.
This study is part of ongoing efforts at Kaiser Permanente to conduct
studies focused on the safety and effectiveness of vaccines. In 2009,
Kaiser Permanente researchers found
that children of parents who refuse vaccines are 23 times more likely
to get whooping cough compared to fully immunized children. Earlier this year,
Kaiser Permanente researchers found that the herpes zoster vaccine,
also known as the shingles vaccine, is generally safe and well
tolerated. Another study
from the Vaccine Study Center this year found that vaccines for measles
were not associated with an increased risk of febrile seizures among
4–6 year olds during the six weeks after vaccination.
Additional investigators on the paper include: Joan Bartlett, MPH, MPP; Bruce Fireman, MA, with the Kaiser Permanente Northern California Division of Research ; Ali Rowhani-Rahbar, MD, MPH, PhD; and Roger Baxter, MD, co-director of the Kaiser Permanente Vaccine Study Center.
The research was funded by Kaiser Permanente.
SOURCE Kaiser Permanente