(Below copied from my response to someone on another thread about this shot)
These are the rare but severe effects found in the study of the HepB Energix B vaccine with a follow up of four days (yes, 4 whole days!) after the shot:
Infections and Infestations: Upper respiratory tract illnesses.
Blood and Lymphatic System Disorders: Lymphadenopathy.
Metabolism and Nutrition Disorders: Anorexia.
Psychiatric Disorders: Agitation, insomnia.
Nervous System Disorders: Somnolence, tingling.
Vascular Disorders: Flushing, hypotension.
Gastrointestinal Disorders: Abdominal pain/cramps, constipation, diarrhea, nausea, vomiting.
Skin and Subcutaneous Tissue Disorders: Erythema, petechiae, pruritus, rash, sweating, urticaria.
Musculoskeletal and Connective Tissue Disorders: Arthralgia, back pain, myalgia, pain/stiffness
in arm, shoulder, or neck.
General Disorders and Administration Site Conditions: Chills, influenza-like symptoms,
injection site ecchymosis, injection site pain, injection site pruritus, irritability, malaise,
weakness.
Post- marketing effects (not clear how common):
Infections and Infestations
Herpes zoster, meningitis.
Blood and Lymphatic System Disorders
Thrombocytopenia.
Immune System Disorders
Allergic reaction, anaphylactoid reaction, anaphylaxis. An apparent hypersensitivity syndrome
(serum sickness-like) of delayed onset has been reported days to weeks after vaccination,
including: arthralgia/arthritis (usually transient), fever, and dermatologic reactions such as
urticaria, erythema multiforme, ecchymoses, and erythema nodosum.
Nervous System Disorders
Encephalitis; encephalopathy; migraine; multiple sclerosis; neuritis; neuropathy including
hypoesthesia, paresthesia, Guillain-Barré syndrome and Bell’s palsy; optic neuritis; paralysis;
paresis; seizures; syncope; transverse myelitis
Eye Disorders
Conjunctivitis, keratitis, visual disturbances.
Ear and Labyrinth Disorders
Earache, tinnitus, vertigo.
Cardiac Disorders
Palpitations, tachycardia.
Vascular Disorders
Vasculitis.
Respiratory, Thoracic, and Mediastinal Disorders
Apnea, bronchospasm including asthma-like symptoms.
Gastrointestinal Disorders
Dyspepsia.
Skin and Subcutaneous Tissue Disorders
Alopecia, angioedema, eczema, erythema multiforme including Stevens-Johnson syndrome,
erythema nodosum, lichen planus, purpura.
Musculoskeletal and Connective Tissue Disorders
Arthritis, muscular weakness.