Vol. 27 - Num. 107
Clinical Reviews
Hypotonic-hyporesponsive episode following immunization with the acellular pertussis combination vaccine
María Tejada Péreza, Enrique Guerra Vilchesb, Paz González Rodríguezb
aMIR-Pediatría. Hospital Universitario La Paz. Madrid. España.
bPediatra. CS Barrio del Pilar. Madrid. España.
Correspondence: M Tejada. E-mail: mariatejadaperez@gmail.com
Reference of this article: Tejada Pérez M, Guerra Vilches E, González Rodríguez P. Hypotonic-hyporesponsive episode following immunization with the acellular pertussis combination vaccine. Rev Pediatr Aten Primaria. 2025;27:283-6. https://doi.org/10.60147/4363f14c
Published in Internet: 09-09-2025 - Visits: 8562
Abstract
Post-vaccination hypotonic-hyporesponsive episodes (HHEs) are characterized by a sudden loss of muscle tone associated with reduced responsiveness to stimuli, skin pallor or cyanosis. This adverse event is mainly described following vaccination against pertussis, with a significantly lower risk associated with the acellular vaccine compared to the whole-cell vaccine.
We report the case of an infant who, following administration of the 2-month vaccines, presented with an unresponsive episode consistent with post-vaccination HHE, with a subsequent favorable outcome.
We emphasize the importance of early recognition of this adverse event, as well as its management and considerations regarding the administration of subsequent vaccine doses.
Keywords
● Acellular pertussis vaccine ● Hyporesponsiveness ● Hypotonia ● Side effect