Background: Hypotonic-hyporesponsive episodes (HHE) were once considered a contraindication to pertussis vaccination.
Methodology: To evaluate the safety of further vaccination, chart review was conducted of 66 children who had experienced an HHE, and who were assessed in one of three special clinics in three capital city tertiary paediatric hospitals. Immediately prior to the HHE, 63 children had received whole-cell pertussis vaccine, three had received acellular pertussis vaccine.
Results: Sixty-four of the 66 children were vaccinated in the special clinic, 59 with pertussis-containing vaccines (55 acellular, four whole-cell), without serious adverse events. There were no HHE after these further vaccinations.
Conclusions: Previously healthy children who experience HHE reactions can safely continue standard vaccination schedules.