Plague World was a comic story from the Doctor Who Annual Vol 1 16 (1982) published by World Distributors.
The plot[]
The Doctor, Adric and K9 arrive on the planet Publius, which is in the grip of a lethal plague which only the planet's ruler, Bemar, is immune to. Bemar is actually a servant of the insectoid Druden, who are feeding on the planet's population, but with the assistance of a local named Kidson (who sacrificed himself to destroy the Druden) our heroes are able to end the threat, curing the plague and seemingly killing Bemar.