Modern vaccines can do quite a lot. Instead of the former one, they today usually protect against several diseases or several stereotypes (subgroups of microorganisms that differ in their antigenic properties.) of a pathogen. Ever-increasing cleaning procedures ensure that side effects can be reduced. “Vaccination is one of the most important and effective preventive measures available in medicine. Modern vaccines are well tolerated and adverse reactions to medicines are only observed in rare cases,” says Robert Koch Institute (RKI).
The idea behind a vaccination is actually quite simple: it is supposed to help the body to defend itself. On the other hand, implementing these projects properly and safely is far from easy: “Long lead times are not uncommon in the production of vaccines,” says Elsie Soto, responsible for vaccines at the pharmaceutical company Pfizer. Producing a conjugate vaccine that works against 13 different serotypes to prevent infection with pneumococcal is a challenge, despite state-of-the-art technology and science: “It’s like making 13 different vaccines. The manufacturing process is divided into 581 individual steps.”
The production of vaccines can be roughly traced in five steps:
- The first thing to do is to produce an antigen to trigger the immune response. For this purpose, proteins or the DNA of a pathogen (viruses or bacteria) must be grown. This happens in cell cultures, in bioreactors or, as in the case of most flu vaccines, in chicken eggs.
- Next, the antigen must be isolated, that is, separated from the cells or proteins in which it has grown. The aim is to “harvest” as much antigen as possible.
- The antigen must then be cleaned. This is done in several processes – depending on the size of the proteins, their binding properties and their biological activity.
- More components are now added. These can be adjuvants to enhance the action of the antigen, or stabilizers to prolong the effective duration of the vaccine. In the case of combination vaccines, additional components are added.
- Finally, the vaccines are bottled and packaged with the utmost care.
Quality control: Nearly 700 tests
Vaccines are subject to special quality controls that run through the entire production process. “We conduct 678 tests for our conjugate vaccine alone before it is released. Quality and safety is our top priority,” says Elsie Soto.
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There are repeated reports of supply bottlenecks in vaccines. The reasons for this can be many – from the failure of a production plant to contaminants that can delay or even prevent the approval of a batch of vaccines. Due to the long lead times, it is usually not possible to procure replacements at short notice. The example of flu vaccines clearly shows this: the total production time is about half a year. The season is usually almost over until a new vaccine is available in significant quantities.
Sometimes, however, it is simply due to the growing demand worldwide – partly because more and more people worldwide have access to vaccines. Actually good news – but also a real challenge for the people and companies responsible for the production of vaccines. It takes time to build up new production capacities. “Depending on the size of the capacity expansion, you have to take four to five years to plan and approve a plant, to acquire the machinery and to hire and train qualified workers,” says Elsie Soto. “A vaccine plant on the green meadow takes a good three years to stand. And the machines for this are not available off the shelf either. The lead times can take up to 20 months.”