Clemens Peter Freiherr

Freiherr

The German titles Freiherr and Freifrau and Freiin are titles of nobility, used preceding a person's given name or, after 1919, before the surname...

 von Pirquet (May 12, 1874–February 28, 1929) was an Austria

Austria

Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...

n scientist and pediatrician

Pediatrics

Pediatrics or paediatrics is the branch of medicine that deals with the medical care of infants, children, and adolescents. A medical practitioner who specializes in this area is known as a pediatrician or paediatrician...

 best known for his contributions to the fields of bacteriology

Bacteriology

Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

 and immunology

Immunology

Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

.

Born in Vienna, he studied theology at the University of Innsbruck and philosophy at the University of Leuven before he enrolled at the University of Graz

University of Graz

The University of Graz , a university located in Graz, Austria, is the second-largest and second-oldest university in Austria....

 where he became a doctor of medicine

Physician

A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...

 in 1900. He started practicing at the Children's Clinic in Vienna.

In 1906 he noticed that patients who had previously received injections of horse serum or smallpox

Smallpox

Smallpox was an infectious disease unique to humans, caused by either of two virus variants, Variola major and Variola minor. The disease is also known by the Latin names Variola or Variola vera, which is a derivative of the Latin varius, meaning "spotted", or varus, meaning "pimple"...

 vaccine had quicker, more severe reactions to a second injection.