The Mercy Brown vampire incident, which occurred in 1892, is one of the best documented cases of the exhumation of a corpse in order to perform certain ritual activities, such as the conduct of 'magical' rites, supposedly for the purpose of banishing an undead manifestation.
In Exeter, Rhode Island, the Brown family suffered a sequence of tragic tuberculosis infections in the last two decades of the 19th century. Tuberculosis was called consumption at the time, and was a devastating and much feared disease.
The mother of the family, Mary, was the first to die of the disease, followed in 1888 by her eldest daughter, Mary Olive.
In 1891, another daughter, Mercy, also contracted the disease, dying in January 1892. Two months later her brother, Edwin, also became sick.
The father, George, believed that one of his dead family members was returning from the grave as a vampire and causing his son's illness. This was in accordance with certain threads of contemporary folklore that linked multiple deaths in one family with undead activity. Consumption was a poorly understood condition at the time, and the subject of much urban myth.
He pursuaded several villagers to help him exhume the bodies. Both Mary and Mary Olive's body had been significantly decomposed over the intervening 4 years. The body of Mercy was still relatively intact. This was taken as a sign that the child was undead, and the agent of young Edwin's condition. In fact, in the cold soil of a New England winter for two months, the lack of decomposition was not surprising.
Mercy's heart was removed from her body, burnt, and the remnants prepared into a potion that was given to the sick Edwin to drink. Unfortunately, despite all his efforts, George was unsuccessful in protecting his son, who tragically died two months later.
Modern medicine has demystified tuberculosis, although it is still held in great fear and shrouded in myth in certain cultures without access to modern medical understanding.
Source: Wikipedia