Vaccines are the cornerstone of pandemic preparedness strategies, but challenges remain, including the unpredictability of the emerging viral strain, limited production capacity for a pandemic vaccine, rapid deployment to meet worldwide demand, and the expiry of stockpiled vaccines during the interpandemic period. Currently, the risk of human infection with avian influenza is very low in the general population, and WHO does not recommend vaccination. The seasonal influenza vaccine does not protect against avian influenza, but it may reduce the likelihood of simultaneous infection with both avian and seasonal influenza viruses.

The initial H5N1 vaccines were produced using the same manufacturing methods and regulatory approval criteria as seasonal influenza vaccines, which involve producing a virus seed stock optimised for growth in chicken eggs and inactivated. These conventional influenza vaccine platforms are inefficient to produce and have low immunogenicity. New egg-independent vaccine approaches that have shown effectiveness in human clinical trials include cell-based virus production, recombinant proteins, and virus-like particles. 

An ideal vaccine for an avian influenza pandemic should induce a robust protective immune response with minimal antigen use, provide cross-protection against viruses from different clades, and be rapidly scalable for global supply in the event of a pandemic. Better, faster and more efficient avian influenza vaccine development has expanded to several different platforms to overcome current limitations. All available technologies will be needed to produce a global supply of vaccines within six months of a pandemic outbreak. 

Some countries have developed and licensed vaccines that could be used for avian influenza. The U.S. FDA licensed three H5N1-focused vaccines in 2007, 2013 and 2020. Additional vaccines have been authorized by the European Medicines Association (EMA) or protection against various H5 influenza viruses. The target population for these vaccines and H5N1 vaccines is not the general public, but individuals at highest risk of exposure, such as those who work with poultry or cattle. 

Pandemic preparedness influenza vaccines are intended for use only once a pandemic has been officially declared. These vaccines may be authorised in advance but cannot be marketed before an influenza pandemic. They must be specifically developed against the viral strain causing the pandemic. Pandemic influenza vaccines can only be fully prepared once the pandemic has begun, because the exact strain cannot be known until a pandemic emerges. During a pandemic, data on vaccine effectiveness and safety must be collected against the circulating strain. These vaccines can be adapted to protect against any pandemic influenza virus strain if required. Several pandemic preparedness influenza vaccines are authorised in the EU and can be rapidly modified in a pandemic situation.