A pertussis outbreak in a Florida preschool in 2013 that affected 26 vaccinated children has raised concerns about pertussis vaccine effectiveness in children under five, according to a report by researchers from the Florida Department of Health and the Centers for Disease Control and Prevention. Only five students in the school including two among the affected did not receive the complete series of vaccinations. The authors say their data suggest recent vaccinations should not prevent physicians from diagnosing, testing or treating people with pertussis like symptoms for the disease.
Dr. Mark Schleiss, Professor of Pediatrics and Director of Division of Infectious disease and Immunology, University of Minnesota (webpage):
Expertise: Vaccines; Pediatric Infectious Diseases; Viral Infections; Molecular Virology
“In this manuscript by Matthias and colleagues, the Florida Department of Health in Leon County (Tallahassee, Florida), in collaboration with the CDC, an outbreak of approximately 40 cases of whooping cough (pertussis) was investigated. The majority of cases were identified in young children age 1-5. The outbreak investigation was centered in a preschool where compliance with pertussis vaccination was excellent. Most of these children were fully vaccinated: only 5 of 117 children in the preschool had not received the complete series of vaccinations. Thus, this outbreak offered a powerful opportunity to examine vaccine effectiveness in the context of a “real-world” outbreak of disease, and not just the context of a clinical trial. Vaccine effectiveness among children attending the preschool was estimated to be a disappointing 45.0%. These findings are not novel. Outbreaks of disease in groups of fully immunized children have been described in the past, including an outbreak in Cincinnati, Ohio reported in 1994 described by Christie and colleagues (Christie et al., N Engl J Med 1994). The overwhelming majority of cases were in fully vaccinated children.
“What does this outbreak from Tallahassee tell us about pertussis? First and foremost, we need to acknowledge that these data in no way imply that current pertussis vaccination strategies lack value. Importantly, there were no deaths in this Tallahassee group. In an outbreak of pertussis in California in 2010, 10 unimmunized and under-immunized infants died of the disease. Therefore, even though current pertussis vaccines may be suboptimal in preventing infection, they do prevent death. Secondly, we need more research on strategies to improve pertussis vaccines. There is evidence that circulating strains of the pertussis organism have evolved to “escape” vaccine-induced immunity. The current generation of so-called “acellular” pertussis vaccines were developed and licensed in the early 1990s in response to demand for vaccines that had fewer side effects (fever, inoculation site swelling) than the first-generation “whole cell” pertussis vaccines. We need to understand if the trade-off for improved safety has been a vaccine with decreased effectiveness. The Tallahassee outbreak, though not unique, reminds us that pertussis remains unsolved, and improved vaccines are needed.”
Dr. James Cherry, Distinguished Research Professor of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles (webpage):
Expertise: pediatric infectious diseases, epidemiology and vaccine prevention strategies of Bordetella pertussis worldwide
“The finding of sustained transmission of pertussis in vaccinated 1-5 children in a preschool in Florida as reported by James Matthias and others is not surprising. However, the results need to be analyzed and put into perspective. The first point to be made is that our present DTaP acellular vaccines containing proteins from the pertussis bacteria are less effective than the whole cell DTP vaccine which we used in the United States until about 1997. This is very clear from historic vaccine efficacy trials carried out in Europe in the early 1990s which showed that the two presently used vaccines in the US had efficacies of 71% and 78%. However, studies by our group in Germany at that time indicated that the even the modest efficacies were overestimates because of bias. From studies in baboons by FDA investigators, we now know the DTaP vaccines are not as good as the DTP vaccines that they replaced because they do not generate the same cellular immune response as DTP vaccines.
“The present report is disappointing in that severity of illness data are not presented. However, from other studies, we know that illness in children who were previous vaccinees (vaccine failures) is less severe than illness in non vaccinated children.
“The present resurgence of pertussis in the US and other regions has three main reasons. The most important reason is greater awareness. Much has been written about pertussis and this attention has led to the finding of cases that would otherwise have been misdiagnosed. The second reason is the use of newer diagnostic tests. The third is the fact that the present DTaP vaccines (which cause less reactions than their predecessors) are not as effective as DTP vaccines.
“However, it is extremely important to note that today the number of cases of pertussis are 20 times less than in the pre-vaccine era. We should continue to use our present vaccines as they are recommended including vaccinating all pregnant women with Tdap. Also of importance is the fact that early treatment of pertussis with the correct antibiotic will shorten the illness and prophylactic use of the correct antibiotic will prevent illness.”
Declared interests (see GENeS register of interests policy):
Dr. James Cherry: JC has given talks on behalf of Sanofi Pasteur which manufactures pertussis vaccines used in the United States.
No further interests declared
‘Sustained Transmission of Pertussis in Vaccinated, 1– to 5-Year-Old Children in Preschool, Florida, USA‘ by James Matthias et al., published in Emerging Infectious Diseases on Wednesday 13 February 2016