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Additional training may be warranted for clinicians administering DTaP

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Transition from DTwP to DTaP offers trade-off between efficacy, safety

The Vaccine Adverse Event Reporting System offers confirmation that DTaP vaccines are safe and have a reasonably low frequency of adverse events. Despite this, the U.S.-based resurgence of pertussis shortly after acellular vaccines were introduced legitimately raised concerns over the efficacy of DTaP, which is now known to have a shorter duration of protection than its predecessor, the diphtheria, tetanus toxoids, whole-cell pertussis vaccine. Consequently, older children, adolescents, and adults are left unprotected without periodic booster doses, Flor M. Muñoz, MD, wrote in an editorial accompanying the study by Moro et al.

The World Health Organization’s recommendation to countries that never made the switch to DTaP is to continue using the whole-cell vaccines “because of their consistent higher efficacy” points to “an imperative need to develop more immunogenic pertussis vaccines that are also safe,” she observed.

“Active research is ongoing for the development of novel vaccines, including live attenuated vaccines, whole-cell vaccines with reduced endotoxin content to be less reactogenic, outer membrane vesicles–based vaccines, and acellular vaccine formulations prepared with new adjuvants or additional and novel antigens.‍

“As we go back to the drawing board in the fight against Bordetella pertussis, much work is needed to learn more about this fascinating pathogen and its interactions with humans to improve our understanding of how immunity and long-lasting protection can be achieved, to engineer and produce novel vaccines, and to design and perform the clinical studies that will eventually lead to the control of pertussis disease and its global impact with safe and effective vaccines for all,” Dr. Muñoz added.

Dr. Muñoz is affiliated with the section of infectious diseases in the department of pediatrics at Baylor College of Medicine and Texas Children’s Hospital, both in Houston. Her comments here were summarized from her editorial accompanying the article by Moro et al (Pediatrics. 2018. doi: 10.1542/peds.2018-1036). Dr. Munoz said she had no relevant financial disclosures and received no external funding.



Additional training may be needed for providers who administer DTaP vaccine to prevent errors in vaccination, but there are no new or unexpected safety concerns surrounding the DTaP vaccine itself, reported Pedro Moro, MD, MPH, of the Centers for Disease Control and Prevention’s National Center for Immunization and Respiratory Diseases and his associates in Pediatrics.

After Dr. Moro and his associates performed an automated analysis of all reports included in the Vaccine Adverse Event Reporting System (VAERS), which is coadministered by the CDC and the Food and Drug Administration, as well as a clinical review of reported deaths and a random sampling of serious reports in the database, they concluded that safety findings concerning DTaP were consistent with those from prelicensure trials and postlicensure studies.

vaccine toddler Yarinca/istockphoto
A total of 50,157 reports involving DTaP vaccines Jan. 1, 1991, through Dec. 31, 2016, were included in the authors’ data mining of VAERS. They set out to identify DTaP adverse events occurring more frequently than expected in children up to 7 years of age.

DTaP vaccines, which included Infanrix, Daptacel, Pediarix, Kinrix, and Pentacel, were coadministered with one or more other vaccines in 43,984 (88%) of cases reported; of the reports included in the data mining, 5,627 (11%) were classified as serious, including 844 (2%) deaths. Of all reports received in the prelicensure clinical trials, injection site reactions and systemic reactions, such as fever and vomiting, were the most common reactions to DTaP vaccine.

In a 5% random sample of the 4,783 serious nondeath reports included in the study, 25% were neurologic, 23% gastrointestinal, and 20% were caused by general disorders and vaccine site conditions. Fully 80% of those flagged as neurologic were seizure related. In another 79%, for which intussusception was the most common gastrointestinal condition, all but two cases had rotavirus vaccine coadministered with DTaP. Altogether, there were 182 cases of anaphylaxis reported.

Serious events were characterized as death, life-threatening illness, hospitalization, lengthening of existing hospital stay, or permanent disability. In cases of death, reports that followed DTaP vaccine were manually reviewed by a physician, who evaluated autopsy report, death certificate, or medical records. The authors also included in their evaluation of records any reports of postvaccine anaphylaxis.

Of the 844 deaths, death certificates, autopsy reports, or medical records were obtained for 86%. Among these, sudden infant death syndrome (SIDS) was found to be the most frequent cause of death in 48%; of these, 62% were male infants, and 91% were infants under 6 months of age.

“It would not be uncommon to observe a coincidental close temporal relationship between vaccination and SIDS because this condition peaks at a time when children receive a relatively large number of recommended vaccinations,” said Dr. Moro and his associates. “There is a large body of evidence in which it is shown that vaccination is not causally associated with SIDS.”

The authors identified disproportional reporting for injection site reactions, as well as other events and conditions, to which they attribute, at least in part, administration of the wrong vaccine or formulation and administration at the wrong site. Such mistakes can be lessened or even prevented with provider education and training on appropriate recommendations and package insert specifications put forth by the CDC’s Advisory Committee on Immunization Practices, they advised.

While the authors praised VAERS for the wealth of timely data it has offered in detecting potential safety issues that may require further investigation, Dr. Moro cautioned that it is a passive surveillance system with limitations that warrant “careful interpretation of its findings.” Its purpose is to improve immunization programs.

Because it does not “meet the definition of research,” the work performed in this study was not subject to institutional review board evaluation and informed consent requirements, the authors added. VAERS generally is not able to assess whether vaccines are the direct cause of adverse events, primarily because of underreporting or overreporting, biased reporting, and inconsistency in quality and completeness of information reported. Because it does not tally number of vaccines administered, it is also unable to provide data needed to calculate incidence rates.

The authors had no relevant financial disclosures. The study was funded by the CDC and the FDA.

SOURCE: Moro P et al. Pediatrics. 2018. doi: 10.1542/peds.2017-4171.

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