Growing a vaccine in an egg
Chickens. Where would we be without them? Well for one thing, we wouldn’t have nearly as many influenza vaccines as we need. Why? Because the humble egg, responsible for many a delicious meal, also plays an essential part in flu vaccine manufacture.
Most people know that peak flu season starts around November (in the northern hemisphere) and March (in the southern hemisphere) every year. What you may not know is that your annual ‘flu jab’ is made up of three distinct strains of the flu virus (or ‘components’), determined each year by the World Health Organisation to pose the greatest risk to human health.
With the declaration for the northern hemisphere vaccine components only coming in February (and for the southern hemisphere in September) it’s a race from that point on to develop, manufacture and deliver the required vaccine, in sufficient quantities and in time to prevent people getting sick.
With so many component parts involved, and so much pressure to deliver on time, the manufacturing process has to be incredibly flexible and adaptable. It requires a highly complex organism capable of adapting to the demands of the ever-changing virus strains. And, although you might not think so from that crusty exterior, these are some of the egg’s strongest attributes.
At the peak of the vaccine production season, our manufacturing facility in Dresden, Germany, receives nearly 400,000 eggs per day. And these are no ordinary eggs. They are produced to the highest standards of quality by 14 ‘dedicated’ flocks located all over the country. Such high quality eggs require the highest quality standards at the farm as well, something which is tightly regulated by German law and by the contractual arrangements we have with our farmers.
This geographic distribution is important as well because it means we can get the quantities we need throughout the season, even if a problem strikes one of the farms or regional areas.
And so, every morning at 6.00am, two large truckloads of these eggs are delivered to the manufacturing facility. During the journey from the farm they are kept in tightly temperature-controlled circumstances (32-35°C), the same circumstances which await them during the manufacturing process. They are then stored overnight and present for ‘work’ first thing the next morning.
The highly complex production cycle begins with ‘inoculation’ which is when the infective agent, or specific strain of flu virus, is introduced into the egg. Next, the eggs are ‘incubated’ which means they are kept at a suitable temperature in order to allow the virus to multiply (this is essential to producing sufficient quantities of vaccine). Once the virus has multiplied, it is then ‘harvested’ or removed from the egg.
This rich raw material, known as flu serum, is then filtered and further processed to obtain the precise level of purity and concentration. Next, the still active flu virus is broken down to contain only inactive parts of the original virus. These inactive parts of the virus are sufficient to provoke a protective response in the human body without actually giving you the disease.
This process is then repeated for the two additional strains of the virus with every step along the way involving rigorous quality testing and confirmation. The final step is to ‘pool’ or combine the three strains of inactive flu virus to form the single vaccine.
Nothing has yet surpassed the egg in its ability to deliver a high quality result, in large quantities, in record time and all at an affordable price.