UNIVERSITY OF CALIFORNIA, SAN FRANCISCO 
BERKELEY • DAVIS • IRVINE • LOS ANCELES • RIVERSIDE • SAN DIECO • SAN FRANCISCO 
SANTA BARBARA • SANTA CRUZ 
SCHOOL OF MEDICINE 
SAN FRANCISCO, CALIFORNIA 94143 
Department of Microbiology 
and Immunology 
14 December 1979 
Dr. Donald Fredrickson 
Director, 
National Institutes of Health 
Bethesda, Maryland 20205 
Dear Dr. Fredrickson: 
I am writing to urge you in the strongest possible terms to approve the 
new version of the NIH Guidelines for Recombinant DNA Research, proposed in 
the Federal Register of November 30, 1979. In particular, I would like to 
emphasize, as have many others, the importance of the section (III-O) which 
would relax regulations governing experiments which employ E. coli K12 host- 
vector systems. There is now ample risk assessment on both sides of the 
Atlantic (from the Rowe and Martin groups here and from Fried et al in Europe) 
to show what the vast majority of microbiologists had long predicted about 
the dangers of recombinant DNA work with this system. Compared with other 
risks of modern laboratory lift' (e.g., chemicals, fires, radioisotopes), 
the risks of this work appear trivial; the likelihood that E. coli K12 can 
behave as a pathogen has always been very small; and the bureaucracy that 
has mushroomed to deal with recombinant DNA is now am impediment to the 
productive pursuit of scientific objectives. The new proposal is a reason- 
able response to such arguments. Ultimately, I believe that even the regis- 
tration of experiments with E. coli K12 can be dispensed with, but the step 
recommended by your Advisory Council seems to me to be a satisfactory begin- 
ning. 
Sincerely 
HAROLD E. VARMUS 
Professor , 
Department of Microbiology 
and Immunology 
HEV:kwj 
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