APHA IMMUNIZATION EXAM 300 ACTUAL
QUESTIONS AND CORRECT ANSWERS
WITH RATIONALE LATEST UPDATE
ALREADY GRADED A+ ASSURED PASS
Section 1: Immunology and Vaccine Types (Questions 1-50)
1. What type of immunity occurs when a person receives antibodies from an
external source, such as through breast milk or immunoglobulin therapy?
A. Active immunity
B. Passive immunity
C. Innate immunity
D. Adaptive immunity
Correct Answer: B
Rationale: Passive immunity occurs when antibodies are transferred from an
external source. This type of immunity is temporary and does not create
immunological memory.
2. How do inactivated vaccines elicit an immune response?
A. By replicating within host cells
B. By using killed pathogens that cannot replicate
C. By using live attenuated pathogens
D. By using bacterial toxins
Correct Answer: B
Rationale: Inactivated vaccines use killed pathogens that cannot replicate but still
stimulate an immune response.
3. Which of the following is an example of a live attenuated vaccine?
A. Hepatitis B vaccine
B. Influenza injectable vaccine
C. Measles, mumps, and rubella (MMR) vaccine
D. Tetanus vaccine
,Correct Answer: C
Rationale: The MMR vaccine is a live attenuated vaccine, meaning it contains
weakened forms of the viruses that can replicate but do not cause disease in
healthy individuals.
4. What is the primary advantage of live attenuated vaccines?
A. They are safe for immunocompromised patients
B. They produce a strong, long-lasting immune response
C. They cannot cause disease
D. They do not require refrigeration
Correct Answer: B
Rationale: Live attenuated vaccines produce a strong, long-lasting immune
response because they closely mimic natural infection.
5. Which of the following is a contraindication for live attenuated vaccines?
A. Pregnancy
B. Mild illness
C. Breastfeeding
D. Age over 65
Correct Answer: A
Rationale: Pregnancy is a contraindication for live attenuated vaccines due to the
theoretical risk of the attenuated virus affecting the fetus.
6. What is the mechanism of action for toxoid vaccines?
A. They use killed bacteria
B. They use inactivated toxins to stimulate immunity
C. They use live attenuated bacteria
D. They use viral vectors
Correct Answer: B
Rationale: Toxoid vaccines use inactivated toxins (toxoids) to stimulate an immune
response without causing disease.
7. Which of the following is an example of a toxoid vaccine?
A. Influenza vaccine
B. Tetanus vaccine
C. Varicella vaccine
,D. Pneumococcal vaccine
Correct Answer: B
Rationale: The tetanus vaccine is a toxoid vaccine that uses inactivated tetanus
toxin to stimulate immunity.
8. What is the purpose of an adjuvant in a vaccine?
A. To prevent allergic reactions
B. To enhance the immune response
C. To preserve the vaccine
D. To reduce side effects
Correct Answer: B
Rationale: Adjuvants are added to vaccines to enhance the immune response to the
antigen.
9. Which of the following is an example of a conjugate vaccine?
A. Haemophilus influenzae type b (Hib) vaccine
B. Influenza vaccine
C. Varicella vaccine
D. Measles vaccine
Correct Answer: A
Rationale: The Hib vaccine is a conjugate vaccine that links a polysaccharide
antigen to a carrier protein to improve the immune response.
10. What is the primary purpose of a booster dose?
A. To increase the initial immune response
B. To maintain immunity over time
C. To prevent allergic reactions
D. To reduce side effects
Correct Answer: B
Rationale: Booster doses are given to maintain immunity over time by stimulating
memory B cells and antibody production.
11. Which of the following best describes herd immunity?
A. Immunity acquired through vaccination
B. Immunity acquired through natural infection
, C. Protection of unvaccinated individuals when a sufficient proportion of the
population is vaccinated
D. Immunity passed from mother to infant
Correct Answer: C
Rationale: Herd immunity occurs when a sufficient proportion of the population is
vaccinated, providing indirect protection to those who cannot be vaccinated.
12. What is the minimum percentage of the population that must be vaccinated to
achieve herd immunity for measles?
A. 50%
B. 70%
C. 95%
D. 100%
Correct Answer: C
Rationale: Measles is highly contagious and requires approximately 95%
vaccination coverage to achieve herd immunity.
13. Which of the following is a barrier defense mechanism of innate immunity?
A. Antibody production
B. Skin and mucous membranes
C. T cell activation
D. Memory B cells
Correct Answer: B
Rationale: The skin and mucous membranes are barrier defense mechanisms of
innate immunity, preventing pathogen entry.
14. What is the role of antigen-presenting cells (APCs) in the immune response?
A. They produce antibodies
B. They present antigens to T cells
C. They directly kill infected cells
D. They produce memory cells
Correct Answer: B
Rationale: Antigen-presenting cells process and present antigens to T cells,
initiating the adaptive immune response.
15. Which of the following is a function of helper T cells?
QUESTIONS AND CORRECT ANSWERS
WITH RATIONALE LATEST UPDATE
ALREADY GRADED A+ ASSURED PASS
Section 1: Immunology and Vaccine Types (Questions 1-50)
1. What type of immunity occurs when a person receives antibodies from an
external source, such as through breast milk or immunoglobulin therapy?
A. Active immunity
B. Passive immunity
C. Innate immunity
D. Adaptive immunity
Correct Answer: B
Rationale: Passive immunity occurs when antibodies are transferred from an
external source. This type of immunity is temporary and does not create
immunological memory.
2. How do inactivated vaccines elicit an immune response?
A. By replicating within host cells
B. By using killed pathogens that cannot replicate
C. By using live attenuated pathogens
D. By using bacterial toxins
Correct Answer: B
Rationale: Inactivated vaccines use killed pathogens that cannot replicate but still
stimulate an immune response.
3. Which of the following is an example of a live attenuated vaccine?
A. Hepatitis B vaccine
B. Influenza injectable vaccine
C. Measles, mumps, and rubella (MMR) vaccine
D. Tetanus vaccine
,Correct Answer: C
Rationale: The MMR vaccine is a live attenuated vaccine, meaning it contains
weakened forms of the viruses that can replicate but do not cause disease in
healthy individuals.
4. What is the primary advantage of live attenuated vaccines?
A. They are safe for immunocompromised patients
B. They produce a strong, long-lasting immune response
C. They cannot cause disease
D. They do not require refrigeration
Correct Answer: B
Rationale: Live attenuated vaccines produce a strong, long-lasting immune
response because they closely mimic natural infection.
5. Which of the following is a contraindication for live attenuated vaccines?
A. Pregnancy
B. Mild illness
C. Breastfeeding
D. Age over 65
Correct Answer: A
Rationale: Pregnancy is a contraindication for live attenuated vaccines due to the
theoretical risk of the attenuated virus affecting the fetus.
6. What is the mechanism of action for toxoid vaccines?
A. They use killed bacteria
B. They use inactivated toxins to stimulate immunity
C. They use live attenuated bacteria
D. They use viral vectors
Correct Answer: B
Rationale: Toxoid vaccines use inactivated toxins (toxoids) to stimulate an immune
response without causing disease.
7. Which of the following is an example of a toxoid vaccine?
A. Influenza vaccine
B. Tetanus vaccine
C. Varicella vaccine
,D. Pneumococcal vaccine
Correct Answer: B
Rationale: The tetanus vaccine is a toxoid vaccine that uses inactivated tetanus
toxin to stimulate immunity.
8. What is the purpose of an adjuvant in a vaccine?
A. To prevent allergic reactions
B. To enhance the immune response
C. To preserve the vaccine
D. To reduce side effects
Correct Answer: B
Rationale: Adjuvants are added to vaccines to enhance the immune response to the
antigen.
9. Which of the following is an example of a conjugate vaccine?
A. Haemophilus influenzae type b (Hib) vaccine
B. Influenza vaccine
C. Varicella vaccine
D. Measles vaccine
Correct Answer: A
Rationale: The Hib vaccine is a conjugate vaccine that links a polysaccharide
antigen to a carrier protein to improve the immune response.
10. What is the primary purpose of a booster dose?
A. To increase the initial immune response
B. To maintain immunity over time
C. To prevent allergic reactions
D. To reduce side effects
Correct Answer: B
Rationale: Booster doses are given to maintain immunity over time by stimulating
memory B cells and antibody production.
11. Which of the following best describes herd immunity?
A. Immunity acquired through vaccination
B. Immunity acquired through natural infection
, C. Protection of unvaccinated individuals when a sufficient proportion of the
population is vaccinated
D. Immunity passed from mother to infant
Correct Answer: C
Rationale: Herd immunity occurs when a sufficient proportion of the population is
vaccinated, providing indirect protection to those who cannot be vaccinated.
12. What is the minimum percentage of the population that must be vaccinated to
achieve herd immunity for measles?
A. 50%
B. 70%
C. 95%
D. 100%
Correct Answer: C
Rationale: Measles is highly contagious and requires approximately 95%
vaccination coverage to achieve herd immunity.
13. Which of the following is a barrier defense mechanism of innate immunity?
A. Antibody production
B. Skin and mucous membranes
C. T cell activation
D. Memory B cells
Correct Answer: B
Rationale: The skin and mucous membranes are barrier defense mechanisms of
innate immunity, preventing pathogen entry.
14. What is the role of antigen-presenting cells (APCs) in the immune response?
A. They produce antibodies
B. They present antigens to T cells
C. They directly kill infected cells
D. They produce memory cells
Correct Answer: B
Rationale: Antigen-presenting cells process and present antigens to T cells,
initiating the adaptive immune response.
15. Which of the following is a function of helper T cells?
