TDAP Vaccine During Pregnancy Protects Infants Against Whooping Cough

MedicalResearch.com Interview with:

Sylvia Becker-Dreps, MD MPH Associate Professor, Department of Family Medicine Associate Director, Office of International Activities (Latin America Focus) Director, UNC Program in Nicaragua University of North Carolina at Chapel Hill Chapel Hill, NC 27599-7595

Dr. Becker-Dreps

Sylvia Becker-Dreps, MD MPH
Associate Professor, Department of Family Medicine
Associate Director, Office of International Activities (Latin America Focus)
Director, UNC Program in Nicaragua
University of North Carolina at Chapel Hill
Chapel Hill, NC 27599-7595

MedicalResearch.com: What is the background for this study? What are the main findings?

 Response: Pertussis (or whooping cough) is a respiratory infection caused by bacteria. It has been becoming more common in the US over the past two decades. Infants are more likely to be hospitalized and die of the disease. They are especially vulnerable in the first months of life because they have not yet had time to complete the DTaP vaccine series themselves. (Currently, infants receive 3 doses of DTaP at 2,4, and 6 months of age.) Immunizing mothers allows the mothers to pass antibodies against pertussis through the placenta and provide passive immunity to infants early in life. In early 2013, the CDC recommended that pregnant women receive a Tdap vaccine in every pregnancy. That recommendation was based on studies of the immune response to the vaccine, not real cases of pertussis.

Our study examined clinical cases of pertussis in over 675,000 infants throughout the US. We found that in the first six months of life, infants of vaccinated mothers (those that received Tdap during pregnancy) had 75% less pertussis hospitalizations and 50% less pertussis cases overall.  Continue reading

End of Honeymoon Period Means Whooping Cough Can Resurge

MedicalResearch.com Interview with:

This Gram-stained photomicrograph depicts numbers of Bordetella pertussis bacteria, which is the etiologic pathogen for pertussis, also known as whooping cough.

This Gram-stained photomicrograph depicts numbers of Bordetella pertussis bacteria, which is the etiologic pathogen for pertussis, also known as whooping cough.
CDC image

Matthieu Domenech de Cellès PhD
Department of Ecology and Evolutionary Biology
University of Michigan, Ann Arbor, MI, USA.
Biostatistics, Biomathematics, Pharmacoepidemiology, and Infectious Diseases Unit
Institut Pasteur, Inserm,
University of Versailles St-Quentin-en-Yvelines,
Versailles, France.

MedicalResearch.com: What is the background for this study? What are the main findings?

 

Response: Our main motivation was to elucidate an apparent paradox: Why has the US experienced a resurgence of pertussis (whooping cough) since the mid-1970s, despite persistently high vaccine coverage? A variety of hypotheses have been proposed to explain this resurgence, but most attention has focused on the potential shortcomings of the new generation of pertussis vaccines (called acellular pertussis vaccines). However, there remains considerable uncertainty about the degree and the mechanisms of protection conferred by pertussis vaccines.

Via a collaboration with the local department of public health, we used detailed surveillance data in the state of Massachusetts to test a number of hypotheses about pertussis vaccines. We found that, although pertussis vaccines are imperfect (in the sense that they do not provide lifelong, 100% protection to 100% of children vaccinated), they are still highly efficacious. Specifically, we estimated that vaccine protection wanes over time, but slowly, with about 85% of children still protected 10 years after vaccination. Despite this high vaccine efficacy, we showed that the resurgence of pertussis was, in fact, to be expected. What happens is that the introduction of routine vaccination leads to an overall reduction in transmission, not only in vaccinated children but also in the population at large. Accordingly, those who escaped vaccination as children (as a consequence of incomplete vaccine coverage or imperfect vaccine protection) increasingly age having also avoided natural infection. As a result, the number of individuals susceptible to contract pertussis gradually increases. Because such people are the “fuel” of epidemics, this sets the stage for pertussis’ resurgence, with increasing incidence among older individuals.

This overall effect is called the “end-of-honeymoon” and means that resurgence is therefore a predictable consequence of incomplete vaccination with efficacious, but imperfect, vaccines. Importantly, these results show that recent trends do not necessarily reflect recent changes in the epidemiology of pertussis. Rather, they may be interpreted as a legacy of past immunization practices, with long-to-manifest effects. This is a significant shift of perspective about pertussis epidemiology.  Continue reading

Immunity to the Acellular Whooping Cough Vaccine Wanes With Time

MedicalResearch.com Interview with:
Dr. Kevin Schwartz, MD MSc
Infection Prevention and Control Physician
Infection Prevention and Control
Public Health Ontario | Santé publique Ontario

MedicalResearch.com: What is the background for this study?

Response: There has been a resurgence of pertussis, or ‘whooping cough’, in several countries and regions since the introduction of the new “acellular” pertussis vaccine in the 1990s to replace the older “whole cell” vaccine. In Ontario, we have not seen large increases but observed a small outbreak in 2012 that affected both unvaccinated people, as well as in those who have been vaccinated against pertussis. Our objective was to evaluate the effectiveness of the current acellular vaccine used in Ontario. We wanted to find out whether immunity wanes with time in the same way as had been previously observed during a large outbreak in California. We also wanted to study the impact of receiving the older ‘whole cell’ vaccine, which we used in Ontario until 1997.

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Timely Pertussis Vaccination Important For Preventing Infant Deaths

MedicalResearch.com Interview with:
Tejpratap S.P. Tiwari, MD
Meningitis and Bacterial Vaccine Preventable Diseases Branch
Division of Bacterial Diseases
National Center for Immunization and Respiratory Diseases
Division of Global HIV/AIDS, Center for Global Health
Centers for Disease Control and Prevention,
Atlanta, Georgia

Medical Research: What is the background for this study? What are the main findings?

Dr. Tiwari: Infants younger than one year old in the United States are at highest risk for severe outcomes from pertussis and death. The first childhood pertussis vaccine dose is recommended at 2 months old, with additional doses in the first year of life at 4 and 6 months. Studies have established that pertussis vaccines can protect against pertussis disease, complications, and hospitalization in infants when 1 to 3 doses are administered by six months old. This study’s findings suggest that the first pertussis vaccine dose and appropriate antibiotic treatment protect infants against death, hospitalization, and pneumonia. Improved on-time infant vaccination (at 2, 4, and 6 months) could potentially prevent up to 1 out of every 4 infant pertussis deaths.
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