How to make sense of pertussis immunogenicity data

Area of Science:

• Immunology
• Vaccinology
• Infectious Diseases

Background:

• Serologic correlates of protection (SCoP) are crucial for vaccine efficacy evaluation.
• Historical data on whole-cell pertussis vaccines showed agglutinogen titers correlated with protection.
• Acellular pertussis vaccines (aP) showed inconsistent SCoP for antibodies against pertussis toxin (PT) and filamentous hemagglutinin (FHA).

Purpose of the Study:

• To review studies investigating serologic correlates of protection against pertussis.
• To evaluate the relationship between pre-existing antibody levels and protection following pertussis exposure.
• To inform regulatory agencies on potential biomarkers for pertussis vaccine licensure.

Main Methods:

• Review of historical and recent pertussis vaccine trials and nested household studies.
• Analysis of antibody titers against specific pertussis antigens (PT, FHA, pertactin, fimbriae).
• Correlation of pre-exposure antibody levels with protection against typical and mild pertussis.

Main Results:

• Whole-cell vaccine trials indicated agglutinogen titers as a correlate of protection.
• Acellular vaccine trials showed postvaccination antibodies against PT and FHA did not correlate with protection.
• Household studies revealed pre-exposure antibodies against pertactin and fimbriae correlated with protection against typical and mild pertussis; anti-PT correlated only with typical pertussis protection.

Conclusions:

• Two studies identified measurable anti-pertactin, anti-fimbriae, and anti-PT antibody levels at exposure as correlates of individual protection against pertussis.
• Establishing reference laboratory standards and minimal response levels for pertussis assays is recommended.
• Postvaccination antibody response rates may serve as surrogate markers for pertussis vaccine protection.