From early in 1942, American medical journal editors and authors joined scientific journal editors and authors already being "self censored".
Like them, they were asked (virtually required) to submit all articles they were uncertain about, to a NAS/NRC advisory for vetting before printing or submitting.
Supposedly the NAS medical sub-committee was only censored the chemistry of penicillin , but in fact this wasn't consistently imposed until March 1943,when it fell in line with the UK's more legally formal move in this direction.
Between January 1942 till late in 1943, this system's real ambition was to successfully keep every "miracle cure" by penicillin out of medical and scientific media - and thus, by reverse osmosis, out of the daily press.
If the American public didn't hear about this miracle drug, then the chemistry-savvy Germans won't either ---- at least not before D-Day, or so the thought went.
I think the key for this method's success was that the OSRD/CMR/COC controlled (a) all the significant new strains and all the new information on how to make penicillin in mass qualities, (b) controlled all supplies of the resulting therapeutic penicillin (c) and as well was busy dangling $500 million in high-overhead contracts to cash and equipment starved university administrators.
So it could successfully tell the university researchers, commercial penicillin firms and the medical accredited investigators, peep one word and no more penicillin/ penicillin information/ cash.
Informally, the OSRD/CMR/COC tried to fend off all requests for stories on this rumoured new wonder drug from non-science journalists, who they had no hold over.
Science journalists - hello William l Laurence ! - were already totally self-embedded in this self censorship. (Color me surprised ...)
General reporters also read popular science stories for possible leads, so with none coming forth on penicillin, they actually made very few such requests.
Of course when a *Hearst* *city desk editor* got a *Pulitzer* for *spot news reporting* for saving the life of a baby with the miracle cure penicillin (and modestly reporting the story as well) , all that changed.
(I always thought the real miracle was the Pulitzer Committee giving a prize to a Hearst paper, the arch enemy of George Pulitzer. That and a city desk editor breaking a Pulitzer-worthy foot leather news story without ever leaving his desk (or phone.)
But what I am not sure of , was Byron Price ever asked by the OSRD/CMR's Dr A.N. Richards to amend his codebooks to ask editors to avoid any any mention of penicillin.
I have a request on this out to a real expert on the American experience with self censorship in WWII....