How the vaccine is made

The flu comes around every year but it is always changing. This means that even if you’ve had it before or been vaccinated against it previously you could still catch it. To fight off these new strains of flu new vaccines have to be prepared, which is a lengthy and complicated process. Work on this begins months before the vaccination programme each October.  Here is the timetable:

February:

The World Health Organisation identifies three flu viruses which are expected to hit in the coming winter and which will need to be countered by the vaccine.

March:

The different kinds of flu strains are grown in special laboratories so they can be sent to the people who make the vaccines.

April:

The vaccine manufacturers inject the flu strains into large numbers of hens’ eggs, which in turn produce a very large amount of flu virus.

May:

The liquid from the eggs is collected put in a machine which spins it very fast. This produces a concentrated soup of flu virus particles.

June:

These particles are treated with chemicals to deactivate them and make them harmless.

August:

The harmless remains of the virus strains are blended together and made into a vaccine. This is then heavily tested.

September/October:

The vaccine is packed, labelled and delivered.