Vaccines and Immunoprophylaxis Practice Questions
20 free Vaccines and Immunoprophylaxis practice questions for the USMLE Step 1. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
A 2-month-old infant receives the DTaP vaccine. Which type of vaccine protects against tetanus?
- A Live attenuated vaccine
- B Inactivated whole organism
- C Toxoid vaccine
- D Conjugate polysaccharide vaccine
Correct answer: Toxoid vaccine
The tetanus vaccine is a toxoid vaccine made from inactivated toxin. It stimulates antibody production against tetanospasmin.
A patient traveling to an area with yellow fever receives the yellow fever vaccine. Which type of vaccine is this?
- A Live attenuated
- B Inactivated
- C Subunit
- D Toxoid
Correct answer: Live attenuated
The yellow fever vaccine is a live attenuated virus vaccine. It generates strong, long-lasting immunity.
A 6-month-old infant receives the Haemophilus influenzae type b (Hib) vaccine. What type of vaccine is this?
- A Toxoid
- B Polysaccharide only
- C Conjugate vaccine
- D Live attenuated
Correct answer: Conjugate vaccine
Hib vaccine is a polysaccharide conjugated to a protein carrier. This enhances T-cell–dependent immunity in infants.
A traveler is exposed to rabies and receives rabies immunoglobulin plus the rabies vaccine. What type of immunity do these provide?
- A Active only
- B Passive only
- C Passive then active
- D Neither active nor passive
Correct answer: Passive then active
Rabies immunoglobulin provides immediate passive immunity, while the vaccine stimulates long-term active immunity.
A patient with chronic lung disease receives the annual influenza vaccine. Which formulation is recommended for adults?
- A Live attenuated intranasal vaccine
- B Inactivated intramuscular vaccine
- C Conjugate vaccine
- D DNA vaccine
Correct answer: Inactivated intramuscular vaccine
Adults, especially those with chronic conditions, receive the inactivated influenza vaccine. The live intranasal vaccine is contraindicated in many adults.
A child with SCID should NOT receive which vaccine?
- A DTaP
- B Hepatitis B
- C MMR
- D Inactivated polio vaccine
Correct answer: MMR
MMR is a live attenuated vaccine and is contraindicated in severe immunodeficiency. Inactivated vaccines are safe.
Which vaccine is recommended to prevent shingles in older adults?
- A Live attenuated varicella vaccine
- B Recombinant zoster vaccine
- C Subunit influenza vaccine
- D Conjugate pneumococcal vaccine
Correct answer: Recombinant zoster vaccine
The recombinant zoster vaccine is preferred for adults over 50 due to strong efficacy. It is non-live and safe in immunocompromised persons.
A pregnant woman should receive which vaccine during each pregnancy?
- A MMR
- B Varicella
- C Tdap
- D Live attenuated influenza
Correct answer: Tdap
Tdap protects infants from pertussis through maternal antibody transfer. Live vaccines are contraindicated in pregnancy.
Which vaccine prevents infection by a virus with circular, partially double-stranded DNA?
- A Hepatitis A
- B Hepatitis B
- C Rotavirus
- D MMR
Correct answer: Hepatitis B
Hepatitis B is a partially double-stranded DNA virus. The vaccine uses recombinant HBsAg to elicit immunity.
A child receives the rotavirus vaccine. Which type of vaccine is it?
- A Inactivated whole-virus vaccine
- B Live attenuated oral vaccine
- C Toxoid-based vaccine
- D Recombinant subunit vaccine
Correct answer: Live attenuated oral vaccine
Rotavirus vaccine is a live attenuated oral vaccine. It induces mucosal immunity in the gastrointestinal tract.
Which vaccine is required for functional asplenic patients due to increased susceptibility to encapsulated bacteria?
- A Hepatitis A virus vaccine
- B Hepatitis B virus vaccine
- C Pneumococcal conjugate vaccine
- D Rotavirus oral vaccine
Correct answer: Pneumococcal conjugate vaccine
Asplenic patients are at risk for infections by encapsulated organisms. The pneumococcal conjugate vaccine provides protection through T-cell–dependent responses.
A healthcare worker is exposed to hepatitis B but has never been vaccinated. What is the recommended post-exposure prophylaxis?
- A Hepatitis B vaccine only
- B Hepatitis B immunoglobulin only
- C HBIG plus hepatitis B vaccine
- D No prophylaxis needed
Correct answer: HBIG plus hepatitis B vaccine
Unvaccinated individuals require both passive (HBIG) and active (vaccine) immunization. This prevents acute infection.
Which vaccine is contraindicated in infants younger than 6 weeks?
- A Rotavirus
- B Hepatitis B
- C BCG
- D Pneumococcal conjugate vaccine
Correct answer: Rotavirus
Rotavirus vaccine is not administered before 6 weeks of age. Other routinely recommended vaccines can be started earlier.
A patient receives a vaccine containing purified polysaccharide antigens that stimulate B cells without T-cell help. Which vaccine fits this description?
- A PCV13
- B PPV23
- C Hib conjugate
- D Tdap
Correct answer: PPV23
PPV23 contains unconjugated polysaccharides, producing a T-cell–independent response. It is less immunogenic in young children.
Which vaccine uses recombinant subunit technology to prevent cervical cancer?
- A HBV vaccine
- B HPV vaccine
- C Varicella vaccine
- D Influenza vaccine
Correct answer: HPV vaccine
The HPV vaccine contains recombinant L1 capsid protein, forming virus-like particles. It protects against high-risk HPV strains.
Which type of vaccine is most effective at producing mucosal IgA immunity?
- A Inactivated vaccine
- B Live attenuated vaccine
- C Subunit vaccine
- D Toxoid vaccine
Correct answer: Live attenuated vaccine
Live attenuated vaccines stimulate replication at mucosal sites, generating strong IgA responses. This improves protection against mucosal pathogens.
A child receives an oral polio vaccine in a country where it is still used. What advantage does OPV have over IPV?
- A Higher overall safety profile
- B Induces intestinal mucosal immunity
- C Cannot revert to neurovirulence
- D Requires only a single dose
Correct answer: Induces intestinal mucosal immunity
OPV induces strong mucosal IgA immunity, reducing viral shedding and transmission. However, it has rare risks of reversion to virulence.
Which vaccine is associated with rare immune-mediated thrombocytopenia and Guillain–Barré syndrome?
- A Influenza vaccine
- B Hepatitis A vaccine
- C Rotavirus vaccine
- D Polio vaccine
Correct answer: Influenza vaccine
The inactivated influenza vaccine has been rarely associated with GBS. The risk is small compared to the risk from influenza infection itself.
A newborn receives intramuscular vitamin K. What type of prevention does this represent?
- A Primary prevention
- B Secondary prevention
- C Tertiary prevention
- D Quaternary prevention
Correct answer: Primary prevention
Vitamin K prophylaxis prevents hemorrhagic disease of the newborn. This is primary prevention since it prevents disease before onset.
Which pathogen requires both pre-exposure and post-exposure prophylaxis in high-risk laboratory workers?
- A Diphtheria
- B Rabies
- C Tetanus
- D Measles
Correct answer: Rabies
Rabies poses high risk to lab workers exposed to infected animals. Both pre-exposure vaccination and post-exposure prophylaxis are recommended.