What are the recommendations for managing Shigella and Varicella infections based on titer results?

Varicella Titers: Interpretation and Management

I need to clarify that your question mentions "shiggle" which appears to be a typo - Shigella is a bacterial pathogen causing dysentery and does not have serologic titers used for immunity assessment. I will focus on varicella (chickenpox) titer interpretation and management, which is what the evidence addresses.

Understanding Varicella Immunity

Evidence of varicella immunity eliminates the need for vaccination or post-exposure prophylaxis. 1 The following constitute evidence of immunity:

• Positive anti-varicella IgG antibody titer 1
• Documentation of 2 doses of varicella vaccine 1
• History of varicella or herpes zoster diagnosed by a healthcare provider 1
• Birth in the United States before 1980 (for non-immunocompromised, non-pregnant patients only) 1

Management Based on Titer Results

If Varicella IgG is POSITIVE (Immune)

No vaccination is needed. 1, 2 Patients with documented immunity require no further intervention for varicella prevention.

If Varicella IgG is NEGATIVE (Non-Immune)

Management depends on the patient's immune status and clinical context:

For Immunocompetent Patients:

• Administer 2 doses of single-antigen varicella vaccine separated by 4-8 weeks 1, 3
• First dose should be given as soon as immunity status is determined 1
• For persons ≥13 years, the two-dose series is mandatory (not optional) 3

For HIV-Infected Patients:

HIV-infected children (ages 1-8 years) with CD4+ percentage >15% should receive 2 doses of single-antigen varicella vaccine 3 months apart 1

HIV-infected adolescents and adults (>8 years) with CD4+ count >200 cells/µL may be considered for vaccination with 2 doses administered 3 months apart 1

Critical considerations:

• Use single-antigen varicella vaccine only, never MMRV combination vaccine in HIV-infected patients 1
• Monitor for postvaccination varicella-like rash and evaluate promptly if it occurs 1
• If clinical disease develops post-vaccination, acyclovir may modify severity 1

For Immunocompromised Patients (Non-HIV):

Vaccination is contraindicated in severely immunocompromised patients 1

Specific thresholds:

• Patients receiving high-dose systemic steroids (>2 mg/kg or >20 mg/day prednisone) should not be vaccinated 1
• May vaccinate once steroids discontinued for >1 month 1
• Patients receiving <2 mg/kg or <20 mg/day prednisone may be vaccinated 1

For Pregnant Women:

Varicella vaccination is contraindicated during pregnancy 1

• Administer first dose postpartum before discharge 1
• Second dose at postpartum visit (6-8 weeks) 1
• Counsel to avoid conception for 1 month after each dose 1

Post-Exposure Management for Non-Immune Patients

If Exposure Occurred:

For vaccine-eligible patients: Administer varicella vaccine within 3-5 days of exposure 1, 4

• Vaccination within 3 days is >90% effective at preventing disease 4
• Even if exposure causes infection, vaccination does not increase adverse event risk 1

For patients with contraindications to vaccination (pregnant, severely immunocompromised): Administer VariZIG within 96 hours (ideally within 10 days maximum) 1

• Contact FFF Enterprises at 1-800-843-7477 for VariZIG 1
• VariZIG may extend incubation period to 28 days 1

Critical Pitfalls to Avoid

• Never use MMRV vaccine in HIV-infected patients - the VZV titer is higher and safety data are lacking 1
• Do not assume immunity based on age alone in immunocompromised or pregnant patients - birth before 1980 only applies to immunocompetent, non-pregnant individuals 1
• Do not delay post-exposure vaccination beyond 5 days - efficacy decreases significantly 1
• Do not administer VariZIG to persons who received 2 doses of vaccine and later became immunocompromised - they already have immunity 1
• Acyclovir is NOT indicated for prophylaxis in healthy individuals after exposure - vaccination is the method of choice 4