Hypotonic-hyporesponsive episode (HHE) | |
---|---|
Symptoms | Hypotonia, hyporesponsiveness, pallor, cyanosis.[1][2] |
Usual onset | 1 minute to 48 hours post-vaccination.[1] |
Duration | 1 minute to 14 days (median 10 hours).[1] |
Causes | Vaccination, most commonly pertussis vaccine.[1] |
Diagnostic method | Based on symptoms.[1][3] |
Differential diagnosis | Vasovagal syncope, seizure |
Prevention | Those who experience an HHE after pertussis vaccination may avoid further pertussis vaccines.[1][4] |
Treatment | Usually resolves on its own, management involves checking the airway, breathing, and circulation, and hospitalization for observation and to rule out other conditions.[5][1][6] |
Deaths | None reported |
A hypotonic-hyporesponsive episode (HHE) is defined as sudden onset of poor muscle tone, reduced consciousness, and pale or bluish skin occurring within 48 hours after vaccination, most commonly pertussis vaccination.[2] An HHE is estimated to occur after 1 in 4,762 to 1 in 1,408 doses of whole cell pertussis vaccine, and after 1 in 14,286 to 1 in 2,778 doses of acellular pertussis vaccine.[3]