APHA Vaccine-Preventable Diseases & Immunology 3

Question 1

Which hepatitis virus is transmitted primarily through the fecal-oral route and does NOT cause chronic infection?

Accepted Answer

Hepatitis A

Answer

Hepatitis A virus is transmitted via contaminated food and water (fecal-oral route) and causes only acute infection, never progressing to chronic hepatitis.

Question 2

In the context of immunology, what does 'seroconversion' mean?

Accepted Answer

The development of detectable antibodies in serum following vaccination or infection

Answer

Seroconversion refers to the point at which detectable antibodies against a specific antigen first appear in a person's serum, indicating a successful immune response.

Question 3

Haemophilus influenzae type b (Hib) most commonly causes which serious invasive disease in unvaccinated young children?

Accepted Answer

Bacterial meningitis

Answer

Before Hib vaccination, H. influenzae type b was the leading cause of bacterial meningitis in children under 5, along with epiglottitis, pneumonia, and septic arthritis.

Question 4

The polysaccharide capsule of Streptococcus pneumoniae is important in vaccine development because it:

Accepted Answer

Allows the bacterium to evade phagocytosis and serves as the target antigen in vaccines

Answer

The polysaccharide capsule prevents phagocytosis, making it a key virulence factor; pneumococcal vaccines target capsular polysaccharides to generate protective antibodies.

Question 5

Which statement best describes the concept of 'original antigenic sin' in immunology?

Accepted Answer

Prior exposure to an antigen shapes future immune responses, sometimes to the detriment of responses to related antigens

Answer

Original antigenic sin describes how the immune system preferentially recalls responses to previously encountered antigens, which may impair optimal responses to related but distinct antigens encountered later.

(APHA) American Public Health Association Immunization Certification Practice Test

(APHA) American Public Health Association Immunization Certification Practice Test

APHA Vaccine-Preventable Diseases & Immunology 3