How vaccines are made, and why it is hard

Nine vaccines against covid-19 have already been approved in one jurisdiction or another, with many more in various stages of preparation. That this has happened within a year of the illness coming to the world’s attention is remarkable. But it is one thing to design and test vaccines. It is another to make them at sufficient scale to generate the billions of doses needed to vaccinate the world’s population, and to do so at such speed that the rate of inoculation can outpace the spread and possible mutation of the virus.

Maximising a bioreactor’s yield is as much an art as a science. The underlying health of the cells involved matters. So do environmental conditions at the manufacturing site.

There are other bottlenecks, too. In particular, the factories in which vaccines are made must be built to a high standard, known as GMP, for “Good Manufacturing Practice”. There is currently a shortage of GMP facilities. Andrey Zarur, boss of GreenLight Biosciences, a firm in Boston that is developing an mRNA vaccine, says his company has employees whose entire job, at present, is to work the phones trying to find GMP facilities in which to make their vaccine. There is though, nothing available. He is therefore looking to buy firms whose vaccines candidates have turned out not to work, simply in order to acquire the facilities in question.