A pregnant woman whose niece lives with her in the same house contracted Varicella. She tested negative for serum antibodies against varicella. What would this mean?

Correct Answer: D. She is susceptible to chicken pox

Serum antibodies against varicella-zoster virus (VZV) indicate prior infection or vaccination-induced immunity. This pregnant woman tested negative for serum antibodies, meaning she has never had chickenpox and has no vaccine-induced immunity. Therefore, she is susceptible to varicella (chickenpox). In India, where varicella vaccination coverage remains variable and many adults acquired natural immunity through childhood infection, a seronegative status in adulthood is relatively uncommon but carries significant risk—especially during pregnancy, where varicella can cause severe maternal complications (pneumonitis, encephalitis) and fetal/neonatal varicella syndrome. The absence of antibodies is the direct marker of susceptibility; immunity requires either prior natural infection (which produces lifelong antibodies) or vaccination. Since she is seronegative, she has neither. This is a straightforward serological principle: negative VZV serology = no immunity = susceptibility to primary varicella infection.

Why the other options are wrong

A. She is susceptible to zoster — This is incorrect because zoster (shingles) only occurs in individuals with prior varicella infection or vaccination—it is reactivation of latent VZV in dorsal root ganglia. A seronegative person has never had chickenpox, so there is no latent virus to reactivate. She cannot develop zoster without first acquiring primary varicella. This option confuses the natural history of VZV: zoster is a consequence of immunity (latency), not susceptibility. B. She is immune to zoster — Immunity to zoster is not determined by serology alone; it requires prior VZV infection establishing latency. A seronegative woman has no latent virus, hence no risk of zoster. While technically she cannot develop zoster (because she has no latent infection), saying she is 'immune to zoster' is misleading—immunity implies protection from a disease she could otherwise get. She is simply not at risk because she lacks the prerequisite infection. C. She is immune to chicken pox — Seronegative status is the opposite of immunity. Antibodies against VZV (whether IgG from past infection or vaccine-induced) confer immunity to chickenpox. Absence of these antibodies means absence of immunity. This option directly contradicts the serological finding and represents a fundamental misunderstanding of what negative serology signifies in the context of varicella.

High-Yield Facts

Mnemonics

VZV Serology Rule Negative antibodies = No immunity = Susceptible. Positive antibodies = Prior infection/vaccination = Immune (and at risk for zoster reactivation if latency established). Zoster Prerequisite Zoster needs latency. Latency requires prior varicella infection. Seronegative → no prior infection → no latency → no zoster risk.

NBE Trap

NBE pairs "seronegative" with "zoster" to trap students who conflate immunity with zoster risk. Students may incorrectly reason: "If she's seronegative, she's not immune, so she's susceptible to zoster"—forgetting that zoster requires prior infection to establish latency, not susceptibility to primary disease.

Clinical Pearl

In Indian obstetric practice, seronegative pregnant women exposed to varicella should receive VZIG or IV acyclovir within 96 hours of exposure—not the live varicella vaccine, which is contraindicated in pregnancy. This distinction is critical for preventing both maternal morbidity and congenital varicella syndrome, which carries high fetal mortality if infection occurs in the first trimester.

_Reference: Park's Textbook of Preventive and Social Medicine (Communicable Diseases section); Harrison's Principles of Internal Medicine Ch. 173 (Varicella-Zoster Virus Infections)_