When should academic papers be censored due to public health/safety concerns?
This is a rising bioethics topic in the area of biosecurity and dual-use developments. Last year there was controversy with H5N1 and censorship.

There is no set policy, though they are being devolped. Most recently there is the United States Government Policy for Institutional Oversight of Life Sciences Dual Use Research of Concern

The IAP Statement On Biosecurity principles state:


  Awareness. Scientists have an obligation to do no harm. They should
  always take into consideration the reasonably foreseeable consequences
  of their own activities. They should therefore:
  
  
  always bear in mind the potential consequences – possibly harmful – of their research and recognize that individual good conscience does
  not justify ignoring the possible misuse of their scientific
  endeavour;
  refuse to undertake research that has only harmful consequences for humankind.
  


The US NIH Office of Biotechnology Activities is often consulted for such research concerns and has a report Enhancing Responsible Science Considerations for the Development and Dissemination of Codes of Conduct for Dual Use Research and has a series of recommendations.

The WHO Laboratory Biosafety Manual does not address publication restrictions/censorship.