Due to the new needs and tasks that faced the National Institute of Hygiene, it was necessary to extend it further. After the reorganization, in 1951 the Institute consisted of 8 departments: Bacteriology and Experimental Medicine, Epidemiology, Food and Water Utilities, Aquatic Hygiene, Nutrition, Hygiene, Chemistry and School of Hygiene, and managed 14 provincial branches and 4 field offices.

During 1951, the issues of some departments quickly developed and exceeded their existing organizational framework. This created the need to organize new institutes and institutions. From the National Institute of Hygiene, serum and vaccine factories were separated to form a Union of Serum and Vaccine Manufacturing. The Chemistry Department has become the basis for organizing the Institute of Drugs, and the Department of Work Hygiene for the Institute of Work Hygiene established in Łódź. In later years, the Institute of Antibiotics (1957) and the Institute of Food and Nutrition (1963) were established, the nucleus of which was the Laboratory of Antibiotics and the Department of Food Hygiene of PZH.

The new PZH statute approved by the resolution of the Council of Ministers of 1952 gave it the rank of a research institute. From the existing regional branches of the PZH, independent organizational units were created – voivodship sanitary and epidemiological stations. The National Institute of Hygiene, on the other hand, has become a scientific institute of the character of a specialist and domestic consultant appointed to conduct scientific research in the field of microbiology, epidemiology and hygiene, training personnel in these fields and supervise the operation of sanitary and epidemiological stations.

In 1953-54, the large and constantly growing Department of Bacteriology and Experimental Medicine was divided into six independent Departments – Bacteriology, Virology, Parasitology, Sera and Vaccine Research, Biochemistry and Antibiotics. In July 1954, the organizational structure of PZH formed 13 plants (Epidemiology, Bacteriology, Virology, Parasitology, Sera and Vaccine Research, Antibiotics, Biochemistry, School Hygiene, Municipal Hygiene, Nutrition Hygiene, Food and Objects Research, Sanitary Education, Disinfection and Disinfection) Deratization and Clinical Research Center, Organizational and Methodological Department, Library and Administrative and Business Department.

The following years brought further transformations of the Institute’s organizational structure resulting from new public health needs. In 1967 new plants were established – Radiological Protection and Radiobiology, Immunopathology, Independent Laboratory of Electron Microscopy and three new scientific and service departments: Department of Scientific Activity Planning and Specialist Supervision, Department of Information and Scientific Documentation with the Library and Didactic Department under the name “Sanitary Study” Hygienic “, which was a continuation of the former School of Hygiene. The Sanitary-Hygienic Study was renamed in 1991 at the Public Health College.

In November 1992, in connection with the liquidation of the Institute of Spa Medicine, the Zakład Tworzyw Uzdrowiskowych was incorporated into the National Institute of Hygiene.

Structural transformations of PZH, the emergence of new organizational units have been and are closely related to the new programs for the prevention and control of disease and the strategy of struggle for health of the population.