Understanding immunological memory

Humans encounter innumerable pathogenic bacteria, viruses and other microbes in their day-to-day activities. While infections from some pathogens can be easily cleared by the innate immune system, others can evade this first line of defense and require the highly specific responses of the adaptive immune system. Vaccines are also able to activate the adaptive immune system to create “memory” conferring long-lasting immunity specific to the pathogen. However, research demonstrates that protective immunity developed naturally and through vaccination may weaken over time.