What are the possible side effects of the chickenpox vaccine in an adult with a history of spinal cord injury (SCI) at levels C7-Th4 and multiple sclerosis (MS) with non-active lesions in the brain and spinal cord?

Chickenpox Vaccine Side Effects in Spinal Cord Injury with Multiple Sclerosis

Critical Safety Concern

The chickenpox vaccine (varicella vaccine) is a live attenuated vaccine that carries specific risks in this patient population, particularly concerning neurologic complications and potential MS activity, though the evidence suggests these risks may be manageable with careful monitoring. 1, 2

Common Expected Side Effects

The most frequently reported adverse events after varicella vaccination include:

• Injection site reactions are the most common side effect, occurring in the majority of vaccinees 1
• Systemic symptoms typically develop within 2-3 days and include fatigue (50% of patients), headache (40%), muscle aches and chills (20%), and fever >100°F (10%) 1
• Mild varicella-like rash may develop at the injection site or generalized, usually self-limited 3
• Lymphadenopathy can occur and typically resolves without intervention 4

These common reactions generally resolve within 2-3 days and require only supportive care with acetaminophen or NSAIDs 1, 4

Serious Neurologic Complications

Given this patient's pre-existing neurologic conditions (SCI and MS), the following serious complications warrant particular attention:

Postvaccinial Central Nervous System Disease

• Postvaccinial encephalomyelitis (PVEM) presents with fever, vomiting, headache, malaise, confusion, seizures, and altered consciousness approximately 11-15 days after vaccination 5
• Pathologic features include perivenous demyelination and lymphocytic infiltration—particularly concerning given the patient's existing MS demyelination 5
• Mortality and morbidity historically range from 15-25% mortality with 25% of survivors experiencing permanent neurologic deficits 5
• No specific treatment exists for PVEM; VIG is not effective for this complication 5

Other Serious Neurologic Events

• Guillain-Barré syndrome has been reported following smallpox vaccination (3 cases per 665,000 vaccinees), typically occurring within 12 days 6
• Bell palsy occurred in 11 cases per 665,000 vaccinees, with 69% in primary vaccinees 6
• Seizures were reported in 8 cases per 665,000 vaccinees, including one death 6

MS-Specific Considerations

Disease Activity Risk

• MS pseudo-relapse may occur due to fever-induced symptom worsening, which can be mistaken for true MS relapse 7
• Prompt fever management with antipyretics and controlled normothermia (targeting 36.0-37.5°C) is essential to minimize MS symptom exacerbation 7
• Limited evidence from a pilot study of 50 MS patients showed 14 improved, 4 worsened, and 29 remained unchanged after varicella vaccination, with 4 developing mild chickenpox 3

Immunomodulatory Therapy Interactions

• Live vaccine administration during MS disease-modifying therapy carries variable risk depending on the specific agent 2, 8
• Case series data from 16 MS patients on natalizumab showed generally good tolerance, though one experienced mild chickenpox infection 2
• Viral shedding risk may be increased with certain immunomodulators, potentially transmitting infection to contacts 9

Spinal Cord Injury-Specific Risks

Autonomic Dysregulation

• Fever management is particularly challenging in SCI patients with injuries at C7-T4 level due to impaired thermoregulation below the injury level
• Autonomic dysreflexia could theoretically be triggered by systemic inflammatory responses, though this is not specifically documented in vaccination literature

Infection Control Challenges

• Impaired sensation below the injury level may delay recognition of local reactions or secondary infections at the injection site
• Reduced mobility may complicate management of systemic symptoms

Red Flag Symptoms Requiring Emergency Evaluation

The following symptoms demand immediate medical assessment:

• Severe headache unresponsive to analgesics, especially if worsening 1
• Altered mental status, confusion, or drowsiness 1, 6
• Seizures or focal neurologic deficits 1, 6
• Fever persisting beyond 5 days 1
• New or worsening MS symptoms that don't improve with fever reduction 7
• Shortness of breath or chest pain 1

Monitoring Protocol

Immediate Post-Vaccination (Days 0-3)

• Monitor vital signs with particular attention to fever development
• Aggressive antipyretic therapy at first sign of fever to prevent MS pseudo-relapse 7
• Assess injection site daily for excessive reaction

Early Period (Days 4-14)

• Peak risk window for serious neurologic complications, particularly PVEM at days 11-15 5
• Daily symptom assessment for headache, confusion, or neurologic changes
• Maintain high index of suspicion for CNS complications given pre-existing neurologic disease

Extended Monitoring (Days 15-30)

• Continue surveillance for delayed neurologic events 6
• Assess MS disease stability to distinguish vaccine effects from disease activity

Management of Complications

Mild Reactions

• Supportive care with adequate hydration and acetaminophen or NSAIDs for fever and pain 1, 4
• Local care for injection site reactions

Severe Complications

• Vaccinia immune globulin (VIG) is NOT effective for postvaccinial encephalomyelitis and should not be used 5
• Intensive supportive care with anticonvulsants and ICU-level monitoring may be required for CNS complications 5
• Infection control precautions to prevent secondary transmission if disseminated disease develops 5, 4

Critical Caveats

• This patient has multiple risk factors (pre-existing CNS disease, spinal cord injury) that may increase susceptibility to neurologic complications, though specific data for this combination is lacking
• The evidence base for varicella vaccination safety in combined SCI and MS is extremely limited, with most data extrapolated from single-condition studies 2, 3
• Risk-benefit assessment must weigh protection against severe varicella infection (which could be catastrophic in this immunologically complex patient) against vaccine-related neurologic risks
• Timing relative to MS therapy is crucial but not addressed in the question—live vaccines are generally contraindicated during high-efficacy immunosuppressive therapy 2, 8