It’s in the middle of a Russian winter so the central heating must have been belting out so much heat for the poor Colonel to open said window.

Umm, it’s your immune system that detects the vaccine and responds to it by developing antibodies specific to the vaccine (and by extension to the actual disease). Just as it would when challenged in real life by the pathogen.

Vaccination basically gives your immune system a several day head start on producing antibodies.