Hypotonic-hyporesponsive episodes after administration of hexavalent DTP-based combination vaccine: A description of 12 cases

ABSTRACT

Hypotonic-hyporesponsive (HHE) episodes are known and recognized phenomena, which typically occur within 48 hours of immunisation..Our aim is to describe 12 cases of HHE brought to the Center of Pediatric Sleep Medicine, with attention to the clinical features of the episode and their follow-up. Medical charts of infants visited between 2005–2015 were reviewed. Twelve infants showed a HHE using HHE using Brighton Collaboration Criteria. All infants received a Hexavalent diphtheria -tetanus -pertussis acellular component -hepatitis B-,inactivated poliovirus- Haemophilus influenzae type-b conjugate vaccine. Five out of 12 were brought to Emergency Department, where 2 were symptomatic (one was hyporeactive, the other had fever). No infant died during the episode, or the follow-up, nor developed neurological disease after subsequent vaccinations. HHE are confirmed as benign events, even after administration of hexavalent vaccination, devoid of negative neuropsychomotor outcome.

KEYWORDS:

• emergency department
• hexavalent
• HHE
• infant
• vaccination
• vagal reaction

Abbreviations

ED	=	Emergency Department
HHE	=	Hypotonic Hyporesponsive Episode
VAERS	=	Vaccine Adverse Event Reporting Systems

Disclosure of potential conflicts of interest

No potential conflicts of interest were disclosed.

Acknowledgments

We would like to thank for their kind collaboration the referents for the Active Surveillance on Sudden Death 0–2 years Network of Regione Piemonte, Italy.

Author contributions

Alessandro Vigo conceptualized and designed the study, wrote the manuscript and approved the final manuscript as submitted.

Giulia Costagliola and Elisa Ferrero were involved in the acquisition and the analysis of the data, wrote the manuscript and approved the final manuscript as submitted.

Silvia Noce was involved in the acquisition and the analysis of the data, wrote the article and approved the final manuscript as submitted.