Answer:
Passive immunity
Explanation:
Active immunity occurs when the immune system of an individual encounters a disease and produces antibodies to fight against it. This type of immunity is usually slow but when achieved the effect lasts for a lifetime.
Passive immunity involves the introduction of antibodies into the body of individuals. The effect is usually instant but it lasts for a short period of time. This explains why every few years, Shelley took her dog in for injection with a rabies vaccine which contained the heat-killed virus.
