Which of the following are examples of a host's intrinsic factors?

The correct choice highlights intrinsic factors that pertain directly to the individual characteristics of a host. The age and gender of a host are fundamental biological and demographic characteristics that can significantly influence their susceptibility to diseases and overall health status. For instance, age can impact immune response, with very young or elderly individuals often being more vulnerable to infections and certain health conditions. Similarly, gender can also affect susceptibility to various diseases due to hormonal differences and different health behaviors.

Intrinsic factors refer to those influences that come from within the host themselves, rather than external environmental factors. Elements such as vaccination status, while crucial for determining immunity and resistance against pathogens, represent an interaction between the host's characteristics and external interventions. Likewise, availability of healthcare and climate conditions like temperature and humidity are environmental factors that affect health but are not intrinsic to the host.

This distinction between intrinsic and extrinsic factors is essential in understanding the dynamics of disease transmission and vulnerability in various populations. Focusing on the individual's innate attributes, such as age and gender, is critical for developing targeted public health strategies and interventions.