The National Influenza Centres are able to analyse and review all of the virus strains that are coming in from around the globe, and can advise the World Health Organization about which ones are most common and which are causing disease.
Each year the seasonal flu vaccine contains three different strains of the flu virus1A vaccine containing four different strains became available for the first time for the 2013-14 season 2.
The flu virus for inactivated vaccines is grown in hen’s eggs. After incubation the virus is harvested from the eggs, and then purified to get the live virus. Hundreds of millions of eggs are needed to produce enough flu vaccine for the season2. This can cause a delay depending on the availability of eggs for production.
The next step is to kill the virus, or inactivate it. After this the virus particle is split up and then the three strains are added together, and a buffer solution is added to make the final formulation of the vaccine.
The three strains need to be added together there can be a risk of delay, because the slowest growing strain will dictate how much vaccine you can make.2
Once there is an inactivated vaccine, it is tested in around a hundred healthy individuals. These tests ensure that the vaccine has a good safety profile, and that when vaccinated people produce enough antibodies to fight off the flu should infection occur. Vaccine production involves very rigorous quality assurance and quality control testing. These tests are carried out both by the manufacturer and external agencies.2All of this means that 70% of the entire vaccine development time is spent on testing.3
The entire process of manufacturing an inactivated vaccine includes reviewing existing production capacity; ordering sufficient pathogen-free eggs to meet production needs; filling, packaging and labelling, prior to supply of vaccine.2
Manufacturing a new vaccine usually takes around two years but for flu vaccines the entire process is compressed into eight months. With such complex and time consuming steps in the process any delay is likely to have a knock on effect, which ultimately impacts on the timing of vaccine availability.123
Information about the flu virus, symptoms, complications and disease patterns can be found at the following sites.
Up-to-date guidelines & advice are available from the Department of Health.
Product information for flu vaccines & antivirals licensed for use in the UK can be accessed via the electronic Medicines Compendium (eMC).
Adverse Events should be reported. Reporting forms and information can be found here. Adverse events should also be reported to the appropriate pharmaceutical company.