Repeat whole cell vaccinations should be avoided after hypotonic-hyporesponsive episodes.

EDITOR—Vermeer-de Bondt et al1 imply that recurrence of hypotonic-hyporesponsive episodes is exceptionally rare and that therefore their occurrence after whole cell vaccination should not be a contraindication for further doses. During the clinical trial on pertussis vaccines in Italy we studied 15 601 infants who received three doses of either a whole cell diphtheria-tetanus-pertussis vaccine, one of two acellular diphtheria-tetanus-pertussis vaccines, or a diphtheria-tetanus vaccine.2 We monitored hypotonic-hyporesponsive episodes within 48 hours of vaccination, …