The Soviet Union used bacteriophage therapy. Why didn't the United States start using it until recently? originally appeared on Quora, the place to gain and share knowledge, empowering people to learn from others and better understand the world. You can follow Quora on Twitter, Facebook, and Google Plus.

I am amazed at the number of science journalists who write the “phage therapy is being revived and may solve the resistance crisis” article over and over again. It is a genre of science reporting that never seems to grow old.

Reporters, or at least their editors, should know better. Calls to revive phage therapy go back to at least 1962 and they all sound the same themes - it is a solution to the antibiotic resistance crisis, the Russians have used it with good effect, a new study is rekindling interest, some new technology is being applied to phage therapy. It would not be much of a challenge for a good AI program to write these stories.

Phage therapy was tried extensively in the West in the 1920s and 1930s. Despite desperate clinical need, it did not work very well, and was largely abandoned before penicillin became available.

Here, in a nutshell, are the hurdles to using phage therapy:

1. Antibiotics work most of the time. And they are cheap. This means that the market is small (phage would be used only as second- or third-line therapy) and pricing power would be low. There is not much hope of making money in phage therapy.

2. Phage are intrinsically narrow spectrum agents. Not only are they restricted to a single bacterial species, but usually to a subset of strains within that species. Dozens of phage strains are thus needed to cover the likely sources of any given infection. The same level of coverage can be attained with 1–2 antibiotics.

3. Phage are cleared rapidly from the bloodstream and provoke a response from the immune system. Using them for a systemic infection would be challenging, and you couldn’t use them a second time on a patient.

4. The phage efficacy data from Russia and elsewhere are crap. Just because a lot of treated patients get better, as most phage “clinical trials” purport, means absolutely nothing. Most infections resolve even without treatment. Placebo-controlled antibiotic trials are rarely done now, due to ethical concerns. But trials from the 1930s and 1940s show 40–80% resolution of infections in the control arm. Let’s agree that supportive care (these were mostly pneumonia patients) is much better now, so that these numbers are lower bounds. A convincing demonstration of efficacy requires very careful trial design, and no one has come close to meeting a modern standard of proof with phage therapy.

Phage therapy is technically feasible, but probably only for certain applications, like diabetic foot ulcers and ear infections. If someone can figure out how to make the economics attractive, it could definitely happen. But it is never going to be a significant alternative to antibiotics, or a solution to the resistance crisis.

Is OTC phage therapy safe and effective?

Lipstick on the Pig

Drew Smith's answer to What are the major hurdles in using phages to treat bacterial infection?

Drew Smith's answer to Why has phage therapy not taken off in the West?

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