Seven manufacturers in the late stages with clinical trials and manufacturing of the vaccine utilizing traditional vaccine technology in order to determine safety and whether two doses are needed. At least five countries have trials underway.
The formulation change for the upcoming season in the US would be to add the H1N1 flu strain (strain change) to the seasonal lflu vaccine.
For pandemic use in Europe, a number of vaccines are under development which utilize an adjuvant that was extensively tested for prototypes of H1N5 (Avian Flu) vaccines in 2007. Forty million doses of adjuvanted vaccines have already been in use in Europe for H5 with no safety concerns. Adjuvanted flu vaccines have never been registered or licensed in the US. (WHO Virtual Press Briefing August 6, 2009)
Manufacturers have begun to submit dossiers to regulators that may be authorized for use in September with more widespread release in October
There have been safety concerns about the Flu vaccine but the WHO position is that it is not possible to have a zero safety concern so there will be adverse events experienced by some people.
Availability of the vaccine may be limited so it will be important to target populations most at risk. Some experts are recommending vaccination of 55 million school age children to stop the Flu from spreading. In a study published in Lancet, CDC scientists found pregnant women most at risk. The WHO said One Billion doses of swine vaccine have been ordered and that there will be limited supply in the early days. US health officials recently estimated that just 45 million of 195 million doses ordered will be delivered by mid-October.