Influenza viruses are part of the Orthomyxoviridae family, and are divided into 3 genera; influenzavirus A, B and C. Types A and B are the most common, therefore only these will be discussed. Members of the type A species of influenza include the strains H1N1, which caused the swine flu epidemic in 2009, and H5N1, which caused the bird flu pandemic in 2004. Type B strains almost only infect humans, are less common, mutate 2-3 times slower and are less genetically diverse, therefore pandemics of influenza B cannot occur.
The most effective way to protect against influenza is by vaccination. Vaccines for influenza have been available since the 1950′s, and are capable of preventing 70-90% of illness. Despite the World Health Organisation vaccination recommending flu vaccination, the proportion of vaccine uptake in the UK remains low.
The advantages of the vaccine is that it is highly protective, free if you are in the at-risk group and easily accessible. However, unlike other vaccine in which one injection in most cases while keep an individual protected for their lifetime, a new influenza vaccine is available every year from September onwards. This is because every year there is a new influenza strain that circulates and becomes dominant, so protection needs to be adjusted accordingly. Influenza epidemics can vary in their timing, severity, length and virus strain, meaning that it is highly unpredictable; this needs to be taken into consideration when designing a new vaccine.
How is a new flu vaccine produced each year?
A new flu vaccine is required to be produced each year due to the virus’ nature of constantly changing. Every winter different strains of flu circulate, meaning that while the symptoms of flu might be similar, it could actually be a different virus that it causing the infection.
In order to prepare for this, action must be taken months in advance of the winter season. Therefore, in February of every year, WHO have to make an assessment of the flu strains that are most likely to be circulating in the northern hemisphere in winter. They do this by continually surveying the pattern of influenza infections through the Global Influenza Surveillance Network (GISN) and through information from advisers from international institutions and laboratories. As well as infection patterns, WHO have to consider the evolving strains of flu virus and strains of influenza virus that have caused sporadic infection, such as avian and swine strains which can cause infections in humans and lead to a pandemic. Influenza strains are also continually assessed for resistance to anti-viral drugs, so that evaluations of the effectiveness of therapeutics can be conducted.
Following this assessment, the three most likely strains are selected for the vaccine. This year the three strains that WHO have recommended to be protected against in the 2011-2012 season in the northern hemisphere are:
• An A/California/7/2009 (H1N1)-like virus
• An A/Perth/16/2009 (H3N2)-like virus
• A B/Brisbane/60/2008-like virus
Flu vaccine production and accessibility
The vaccine is manufactured by growing the three selected strains in hen’s eggs. The viruses are then killed and purified and made into a vaccine. As the virus strains are killed, and the virus is not live, it is not possible to develop flu from the vaccine. The flu jabs are available from local GP surgeries, Boots drug stores and are even now offered to your office by a company run by the Fleet Street Clinic, London.
In summary, flu is a highly infectious disease which can be prevented through vaccination. As it is a virus, antibiotics are not effective and therefore vaccination is the main protection. Individuals in the at-risk group are highly advised to have the vaccination to prevent the severe diseases that can occur from influenza infection. Individuals not in the at-risk group can pay privately for the vaccination; the immune systems of these individuals should be strong enough to fight of influenza protection within one week.
Finally, may I ask everyone to take an extra minute to look at the link below and sign up for the FluSurvey. This is an independent flu infection tracking website, which measures flu trends in the UK directly from the general public, with the aim of gaining more accurate information on flu epidemics in order to predict and prevent them. See website: http://flusurvey.org.uk/en/