Photo Credit PHIL
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A year after the 2009 pandemic started, vaccine manufacturers began delivering a seasonal trivalent influenza vaccine (TIV) with this newly emergent H1N1 strain included.
Australia was among the first to receive this new formulation in the spring of 2010.
Within weeks it became apparent that a significant number of young Australian children receiving a specific brand of flu shot - FluVax or FluVax Junior (CSL) - developed adverse reactions. Most of the side effects were mild and related to fever, but some children experienced potentially serious febrile convulsions.
Other symptoms included nausea and vomiting, or injection site inflammation (see Australia Investigating Adverse Vaccine Reactions).
For a while, Australia placed a moratorium on dispensing flu shots to children under the age of 5, but that was lifted after investigations found the problem was only linked to one manufacturer (see Australia Lifts Ban On Flu Vax For Under Five’s).
Since then, Australia, the United States, and Great Britain have recommended that CSL’s vaccine not be used in children under the age of 5 (see FDA Approves 2010-2011 Flu Vaccines) and cautioned for those aged 5 to 9, and investigations into the cause of these adverse reactions have continued.
Fast forward two years, and today we have a report from CSL Biotherapies that describes, at least in general terms, what appears to have gone wrong.
The details are presented in a press release and a series of supporting documents, including an Investigation summary. Some excerpts (in blue) from that summary follow:
After ruling out bacterial or chemical contamination as the cause, the focus moved to CSL’s manufacturing process, and there they found (in animal models and in vitro systems):
- CSL’s influenza vaccines, as a class, trigger a greater immune gene response and induce higher levels of immune-stimulating hormones (cytokines) compared to other manufacturer’s influenza vaccines
- Fluvax® 2010 induces higher levels of immune-stimulating hormones (cytokines) compared to previous season’s formulations of CSL’s influenza vaccine
- The B strain followed by the H1N1 strain used in Fluvax® 2010 induces the strongest activity in the paediatric blood samples.
The reasons for these differences, CSL believes, include but may not be limited to:
CSL’s method of manufacture preserves more short gene fragments and lipids from the virus than other manufacturers.
The particular characteristics of the gene fragments and/or lipids from the swine flu strain and the B strain used in Fluvax® 2010 may have led it to being more reactive in some young children in 2010 compared to CSL’s vaccines in previous seasons.
The gene fragments and lipids appear to be from split virus, but residual whole virus or clusters of both may have also contributed, and are under further investigation.
Increasing the amount of splitting agent (TDOC) reduces the amount of short gene fragments and lipids in the CSL vaccine, and also reduces the reactivity of the CSL vaccine (in vitro).
The scientific studies indicate that the root cause of the severe febrile response seen in some young children after vaccination with Fluvax® in 2010 is complex and multi-factorial.
CSL continues their investigation, and is looking at ways to remedy the problem. Until they do, they plan no immediate changes to their manufacturing process, and recommend their vaccines for children over the age of nine.
While there are a number of news stories on the wires this morning, the always excellent Jason Gale, writing for Bloomberg News has some of the most complete coverage that I’ve seen.
Convulsion Risk From CSL Flu Vaccine Linked to Components
By Jason Gale on June 20, 2012
Convulsions in children immunized with a CSL Ltd. (CSL) flu shot probably were caused by an excessive immune response to viral components in the vaccine, according to preliminary findings of a two-year study.
It is worth noting that In the summer of 2011, the Medical Journal of Australia (MJA) published a letter that looked at early flu-season testing of several non-CSL TIVs (Trivalent Influenza Vaccines) given to thousands of children under the age of 5.
Ensuring safety of the 2011 trivalent influenza vaccine in young children
Christopher C Blyth, Tracy Y Markus, Paul V Effler and Peter C Richmond
As expected, a small number of febrile reactions were observed, but none proved serious, and none required professional medical attention.
Their reassuring finding was that the pediatric flu shots manufactured by both Sanofi Pasteur and Solvay proved to be very safe when administered to young children, with no repeat of the significant number of adverse reactions reported in 2010.
While no vaccine (or drug) can be said to be 100% safe – and rare but sometimes serious adverse effects have been reported - the preponderance of evidence continues to support the scientific consensus that flu vaccines are very safe and most years, reasonably effective.
Given that influenza-related illnesses claims thousands of lives each year in the United States (cite Estimating Seasonal Influenza-Associated Deaths in the United States), the smart money is on getting the vaccine every year.
For more on flu shot safety and benefits, you may wish to revisit:
