Varicella is caused by the varicella-zoster virus (VZV), which also causes shingles (herpes zoster). The virus typically affects children aged 2‒8 years.
Rubella is a mild febrile rash illness caused by rubella virus. It is transmitted from person to person via droplets (the virus is present in throat secretions). It affects mainly, but not only, children and when pregnant women are infected, it may result in malformation of the foetus. Humans are the only reservoir of infection.
Pertussis, also known as whooping cough, is a highly contagious acute respiratory infection, caused by the bacterium Bordetella pertussis. The disease is characterised by a severe cough, which can last two months or even longer.