Effect of erythromycin treatment on antibody responses in pertussis.

The effect of erythromycin treatment on antibody responses to Bordetella pertussis filamentous haemagglutinin (FHA) and pertussis toxin (PT) was investigated in convalescent blood samples from 105 children with pertussis. Erythromycin had been given to 59 children, median age 3.2 years (range 0.3-9.9) on median day 7 (range 11-14) after onset of disease while the remaining 46 children, age 3.45 (0.6-8.1) were untreated. No significant differences in IgG antibody concentration were noted to FHA by ELISA and to PT, neither by NT nor by ELISA, but a tendency towards lower median titers was seen to both antigens and by both type of assays in the erythromycin-treated group. Similarly, early erythromycin treatment i.e. within 7 days of onset of symptoms, did not influence significantly of the development of the antibody responses but tended to lead to lower titer levels. A significant response to PT and FHA was found in about 90% of blood samples, irrespective of treatment. All 56 children with culture-confirmed B. pertussis infection had a significant response to PT. The study has thus shown a slight but not significant effect of erythromycin treatment on antibody responses in pertussis.