From the Journals

Waning vaccine immunity linked to pertussis resurgence



The resurgence of whooping cough in the United States could be the result of waning pertussis immunity combined with incomplete historical coverage, researchers said.

In the March 28, 2018, edition of Science Translational Medicine, researchers reported on a study that used different models of transmission to explore what might be the cause of the steady increase in pertussis infections since the mid-1970s.

A photomicrograph of Bordetella (Haemophilus) pertussis bacteria using Gram stain technique. copyright CDC
The three modes of vaccine failure modeled in the study were primary vaccine failure in a fraction of the population; waning of vaccine-induced protection over time; and failure in the degree of protection offered by the vaccine, perhaps caused by antigenic evolution in the pertussis bacteria.

Using 16 years’ worth of detailed, age-stratified incidence data from Massachusetts, researchers found that the model which assumed a gradual waning in protection was the best fit for the observed patterns of pertussis incidence across the population.

This model suggested significant variability in how the level of protection changes over time, with a 10% risk of vaccine protection waning to zero within 10 years of completing routine vaccination and a 55% chance that the vaccine would confer lifelong protection.

“Crucially, we find that the vaccine is effective at reducing pathogen circulation but not so effective that eradication of this highly contagious bacterium should be possible without targeted booster campaigns,” wrote Dr. Matthieu Domenech de Cellès, PhD, of the Institut Pasteur at the University of Versailles (France) and his coauthors.

The model also considered the possibility that the whole-cell and acellular pertussis vaccines might show differences in immunity, which had been suggested as one explanation for the resurgence of the disease. However, the authors found little evidence of a marked epidemiological switch from the whole-cell to acellular vaccines, although their results did suggest the acellular vaccine has a moderately reduced efficacy.

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