Vaccine-Preventable Diseases & Immunology Flashcards

Which of the following best describes the difference between T-dependent and T-independent antigens in vaccine immunology?

Answer: T-dependent antigens (proteins) elicit memory and class switching via T-helper cells; T-independent antigens (polysaccharides) produce weaker responses without memory in young children

Protein antigens (T-dependent) engage T-helper cells to drive B-cell class switching and memory formation; pure polysaccharide antigens (T-independent) cannot engage T cells in infants under 2, which is why conjugate vaccines link polysaccharides to carrier proteins.

A pregnant woman at 27 weeks gestation is found to be rubella non-immune. What is the appropriate management?

Answer: Document the non-immune status and administer MMR vaccine postpartum before discharge

MMR is a live vaccine contraindicated in pregnancy; a non-immune pregnant woman should be vaccinated postpartum (ideally before hospital discharge) and counseled to avoid rubella exposure during pregnancy.

Yellow fever vaccine is a live attenuated vaccine that carries a rare but serious risk of:

Answer: Yellow fever vaccine-associated viscerotropic disease (YEL-AVD), a potentially fatal multi-organ failure

YEL-AVD is a rare but severe adverse event where the vaccine virus disseminates and causes multi-organ failure similar to wild-type yellow fever disease, with highest risk in immunocompromised individuals and those over 60.

Which immunoglobulin class is most important for long-term vaccine-induced humoral immunity and is the predominant antibody in secondary immune responses?

Answer: IgG

IgG is the most abundant serum immunoglobulin, responsible for long-term protection after vaccination; it predominates in secondary (anamnestic) immune responses and can cross the placenta to provide neonatal protection.

Measles encephalitis occurs in approximately what proportion of measles cases and carries a high mortality rate?

Answer: 1 in 1,000 cases

Acute measles encephalitis complicates approximately 1 in 1,000 measles cases and carries a mortality rate of about 15%, with up to 25% of survivors experiencing permanent neurological damage.

The oral cholera vaccine primarily stimulates which arm of the immune system to provide mucosal protection?

Answer: IgA-mediated mucosal immunity at the intestinal surface

Oral cholera vaccines primarily induce secretory IgA at mucosal surfaces of the intestine, which blocks Vibrio cholerae colonization and toxin binding at the site of infection.

Which of the following is a 'cold chain' failure scenario that would most likely render vaccines ineffective?

Answer: Varicella vaccine accidentally exposed to temperatures above 8°C for several hours before administration

Varicella vaccine is particularly heat-sensitive; exposure to temperatures above 8°C can inactivate the live attenuated virus, rendering the vaccine ineffective even if it appears visually unchanged.