Winter months earlier this year in the Southern Hemisphere witnessed an unusual upsurge in the number of flu cases. In Hong Kong, hospital occupancy during this year’s flu season back in May – July remained consistently above 100%1. On the other hand, Australia recorded a total of 221,853 flu infections this year, which is more than any other seasons2. As winter approaches the Northern Hemisphere, many in the medical world are bracing themselves for another onslaught.
“If you were to start now with a new vaccine for flu – would it be grown in eggs?”What makes 2017 so different? For one, the majority of flu outbreaks this year appear to be brought on by H3N2, a particularly virulent strain of influenza A. To make matters worse, scientists believe that a flaw in the flu vaccine manufacturing process may be seriously tampering with its efficacy4.
The humble egg has carved out a solid niche for itself in the flu vaccine production process. For the last 70 years, eggs have been used as a medium to grow selected flu virus strains, with the yolky contents purified to produce the vaccine4. This time, however, the virus seems to have outsmarted us.
Scientists believe that after decades of egg-based production, the H3N2 virus has finally developed certain mutations that confers it extra protection from being recognised by our immune system. By some estimates, this year’s vaccine is thought to be only 33% effective against H3N2 – a far cry from the already measly efficacy of 60%4.
What’s even more worrying is that all viruses are more likely to develop these mutations – or better termed as antigenic changes – when grown in eggs5.
“We need to do a lot to improve existing vaccines. And getting away from eggs would be very valuable,” comments Dr Kanta Subbarao, director of the World Health Organisation’s (WHO) Collaborating Centre for Reference and Research on Influenza, in Australia3.
Diversifying vaccine production strengthens capabilities in combating mutant strainsThis unexpected turn of events has sparked intense discussion on diversifying manufacturing methods. What are our other options?
Current, alternative vaccine producing technologies include cell-based methods and recombinant methods. The former uses animal cells instead of eggs that serves as the hosts to viral replication, while the latter forgoes viruses and eggs completely – and instead relies on viral proteins in its production3.
Nevertheless, complete shifts to these forms of vaccinations are unlikely to occur. Firstly, available evidence that these alternatives perform better than traditional egg-based methods are scarce. At such high production costs, many manufacturers are unwilling to take their chances.
Furthermore, flu vaccine producers may instead be holding back, waiting for a breakthrough ‘cure’ for influenza to be discovered; instead of investing millions of dollars in solutions that fare no better than current solutions3.
Ultimately, a complete shift in production methods may leave us shorthanded should a new flu strain materialise.
“Some [flu viruses] might grow well in eggs and some well in cells, and some better in recombinant systems,” says Rick Bright, director of the Biomedical Advanced Research and Development Authority in the United States. “So, that’s been part of our strategy to make more capacity available domestically, and also to diversify this for the various unpredictable attributes of influenza3.”
When hard science meets predictionFlu experts from around the world convene twice a year to predict and select virus strains to be mass produced into the coming year’s flu vaccines. Despite the costly and logistically complicated venture, it’s what’s necessary to keep up with the frequently mutating virus. Even experts who have spent years in the game shake their heads when asked to predict trends of coming seasons6.
Our best efforts seem to barely be enough to keep influenza at bay. Given the recently discovered risk that eggs pose, it may well be time to ramp up research and development in finding more efficient methods. MIMS
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