Vadim was a villager of Klimtenburg during the 19th century, and he claimed to be a doctor. He discovered pieces of metal which, unbeknownst to him, were fragments of the Hapthoid reactor from a Cyberman spaceship which had crashed in Klimtenburg some centuries prior. His wife Nefta turned the metal into jewellery and gave it to a number of the other villagers, causing them to become ill with Hapthoid Radiation Sickness. Before the Eleventh Doctor arrived and investigated the issue, the sickness was believed to be a plague, and Vadim and Nefta were among its earliest victims.
According to Old Nicolai, Olga Bordmann knew Vadim more than any other villager. (PROSE: Plague of the Cybermen)