What CIC Questions and Answers feature?

Chickenpox (varicella) is primarily spread through airborne transmission, and exposure is defined by being in the same airspace with a contagious person (from 1-2 days before rash onset until lesions are crusted), even if briefly.

The APIC Text states:

“Significant exposure is defined as being in the same room or airspace during the period of infectivity, regardless of duration”.

This reflects airborne precaution definitions and CDC exposure management guidelines for varicella.

The Certification Study Guide (6th edition) defines passive immunity as protection that results from the administration of preformed antibodies, rather than stimulation of the individual’s own immune system. Passive immunity provides immediate but temporary protection, because the recipient does not produce antibodies and therefore does not develop immunologic memory.

Tetanus antitoxin is a classic example of passive immunity. It contains antibodies that neutralize tetanus toxin directly and is used in situations where immediate protection is needed, such as after certain wounds in individuals with unknown or inadequate vaccination history. The study guide emphasizes that passive immunization is particularly important in post-exposure management when waiting for an active immune response would be too slow to prevent disease.

The other options represent active immunization, not passive immunity. Vaccines such as hepatitis B vaccine, influenza vaccine, and human diploid cell rabies vaccine stimulate the recipient’s immune system to produce its own antibodies and immune memory. While rabies immune globulin provides passive immunity, the rabies vaccine itself is an active immunizing agent.

This distinction between active and passive immunity is a frequently tested CIC exam concept, especially in the context of occupational health, post-exposure prophylaxis, and immunization programs. Recognizing that passive immunity involves antibody products (antitoxins or immune globulins) rather than vaccines is essential for accurate infection prevention decision-making.

The Certification Study Guide (6th edition) explains that the probability of infection after an exposure is influenced by several factors, including the dose of the infectious agent, the route of exposure, and host susceptibility. Among the options provided, an unknown concentration of infectious virions introduced via a needlestick injury represents the greatest increase in infection risk.

Percutaneous injuries, such as needlesticks, provide direct access to the bloodstream, bypassing natural protective barriers like intact skin. The study guide emphasizes that when the inoculum (number of organisms) is unknown, particularly in bloodborne exposures, the risk of transmission for pathogens such as hepatitis B virus, hepatitis C virus, and human immunodeficiency virus is significantly higher. This uncertainty necessitates immediate evaluation and consideration of post-exposure prophylaxis.

The other options describe situations with lower or reduced risk. Prior immunization for hepatitis B is protective and therefore decreases susceptibility. Exposure of clothing alone does not constitute a significant transmission route unless there is penetration to skin or mucous membranes. Blood splashes onto intact skin are considered low-risk because intact skin acts as an effective barrier against infection.

CIC exam questions frequently test understanding of exposure routes and inoculum size. Recognizing that percutaneous exposure with an unknown infectious dose poses the highest risk is essential for accurate risk assessment and appropriate occupational health response.