Every year, we see those signs pop up reminding us to get our yearly flu shot. If you have ever wondered how they make each year’s shot, read on.
In 1938, the first flu vaccine was created by Jonas Salk and Thomas Francis, and was used to protect soldiers who fought in World War II. Vaccines were improved from the 1940s to the 1960s, but still were not as purified as vaccines are today. Side effects of fever and aches were common, and were blamed on the flu shot.
However, the flu shot has always been made from non-live virus, so flu shots cannot give you the flu. The side effects some have to the flu shot are from one’s own body building an immune response.
Flu nasal spray like FluMist is made from weakened virus so is only recommended for those without health problems, those aged 2 to 49 years old, and those who meet other restrictions.
Prior to 2009, there had not been a widespread outbreak of swine flu in humans. The outbreak started in Mexico and by June, had spread to 74 countries.
“On Oct. 25, 2009, President Obama declared a national emergency as a result of the outbreak,” which had reached 46 states in the United States, reported Emedicinehealth.com.
A new vaccine against the H1N1 virus was quickly made. The swine influenza virus H1N1 was named based on the two main proteins in the flu virus hemagglutinin and neuraminidase.
A second strain called H3N2v needed to be added to the swine flu vaccine due a mutation of the virus. Each year, there are only a few flu virus strains that circulate, but viruses can continue to mutate through alterations in the eight RNA strands that make up the influenza virus genome.
The yearly seasonal flu shot is made up from strains that currently have been circulating worldwide. Labs from 142 National Influenza Centers in 113 countries study influenza disease trends and send influenza viruses to five World Health Organization Collaborating Centers for Reference and Research on Influenza.
The researchers then decide what flu viruses are likely to be the major cause of flu illness for that year. In the United States, the FDA determines which vaccine viruses will be used in U.S. licensed vaccines.
The flu shot needs to be taken every year, as our bodies may not have an adequate response to the current flu strain from a previous year’s shot.
In addition, our body’s antibody response decreases over time so even if the flu virus was the same for the current year, we may not be protected.
There are three different technologies used to make flu vaccines that meet the approval of the FDA.
1) Egg-based Vaccines
For over 70 years, egg-based manufacturing has been used to create inactivated (killed) vaccines for the flu shot and the live (weakened) vaccine in the nasal spray.
The live viruses are injected into fertile hen eggs and allowed to grow and duplicate. The viruses produced are then killed if they will be used in a flu shot, and weakened if used for the flu nasal spray.
Many batches are needed so a number of manufacturers produce the flu shot with different batch and lot numbers, to be ultimately approved by the FDA prior to shipment. The use of egg production takes a lot of time — months.
2) Cell-based Vaccines
In 2012, the FDA approved the use of cell-based production. Flu viruses are set up to start growing in hen eggs but then are transferred to mammalian (animal) cells for them to duplicate. The virus in the fluid from these cells is purified so that only the virus antigen is present. The use of cell-based vaccines takes less time than egg-based.
There is only one company that currently is approved to produce this cell-based vaccine called Flucelvax. It is only approved for use in those 18 years of age or older.
3) Recombinant Flu Vaccines
Recombinant technology used to make flu vaccines was approved in 2013 by the FDA. There are no eggs or animal cells used to make these vaccines. Instead an influenza virus protein, hemagglutinin (HA) is isolated, grown in insect cells and purified.
Currently there is only one company making this type of vaccine called Flublok. It too is recommended for those over the age of 18. It takes the least time to produce.
There are also two types of flu shots available. Versions are made using all three types of the above technologies.
1) Trivalent flu vaccine: protects against two influenza A viruses (an H1N1 and an H3N2) and an influenza B virus.
2) Quadrivalent flu vaccine: protects against the two influenza A viruses and two influenza B viruses.
The CDC recommends that everyone aged 6 months and older should get a flu vaccine every year.
Sources:
1) History and Development of Flu Vaccines. Emedicinehealth.com. Retrieved Dec. 13, 2015.
http://www.emedicinehealth.com/flu_vaccine/page2_em.htm and http://www.emedicinehealth.com/swine_flu/page4_em.htm
2) Pandemic Flu History. Flu.gov. Retrieved Dec. 13, 2015.
http://www.flu.gov/pandemic/history
3) The 2009 and 2011 Outbreaks of Swine Influenza. Emedicinehealth.com. Retrieved Dec. 13, 2015.
http://www.emedicinehealth.com/swine_flu/page2_em.htm#the_2009__and_2011...
4) Flucelvax: First seasonal vaccine using cell-culture technology. American Pharmacy Association. Retrieved Dec. 13, 2015.
http://www.pharmacist.com/flucelvax-first-seasonal-vaccine-using-cell-cu...
5) Key Facts About Seasonal Flu Vaccine. Center For Disease Control and Prevention. Retrieved Dec. 13, 2015.
http://www.cdc.gov/flu/protect/keyfacts.htm
Michele is an R.N. freelance writer with a special interest in woman’s healthcare and quality of care issues.
Edited by Jody Smith