The H1N1 virus is no longer front page news, and the World Health Organization (WHO) has not classified the current outbreak as a pandemic despite 40 countries collectively reporting over 10,000 cases, including 79 deaths. Most epidemiologists agree that widespread transmission of H1N1 is inevitable, and that a more virulent strain may emerge in the fall.  This sobering prediction and the 5 to 6 month lead time to produce a vaccine, beg the question: “Why hasn’t development started?”

There are multiple reasons. For one, the conventional flu may pose more of a global threat than this new strain. According to a recent Los Angeles Times article, mass production of a new H1N1 vaccine could sharply curtail the amount of seasonal flu vaccine available because the new vaccine would be made instead. The WHO, in consultation with manufacturers, is responsible for making this decision. It’s a difficult call because seasonal flu kills 250,000 to 500,000 people each year worldwide (36,000 in the U.S.). So going full steam ahead on a novel H1N1 vaccine presumes the swine flu virus would have an even higher mortality rate.

Another consideration is timing the selection of the H1N1 strain used in development. Because the genetic composition of new flu strains is constantly evolving, premature selection of a strain could render a new vaccine ineffective.  Of course, waiting too long might not allow enough time to manufacture a vaccine to prevent a pandemic.

Compounding this dilemma, one of the key variables in producing a new vaccine is how well the virus can be grown in culture.  According to the WHO, disappointing lab results to date indicate that vaccine manufacturers will not be ready to produce a swine flu vaccine until mid-July at the earliest. If this assessment proves true, a vaccine will not be ready until January, 2010–three months into the flu season.

Finally, mass distribution of the vaccine will not take place until it is clear that the evolving H1N1 virus results in significant morbidity and/or mortality this autumn. Once the vaccine begins to be administered, world health officials will vigilantly watch for any incidence of Guillain Barre syndrome, a complication that affected hundreds of recipients following the mass administration of another swine flu vaccine in 1976. The WHO and CDC want to make sure we don’t once again hatch a cure that is worse than the disease.