WRAP OF THE REST

What about other vaccines? The Sinopharm and Sinovax vaccines, both developed in China, use the older-school, inactivated virus method. The Us-developed Johnson & Johnson vaccine uses an adenovirus vector, like Astrazeneca, but unlike Astrazeneca it only needs one dose. Sputnik V, developed in Russia, is a two-dose adenovirus vector vaccine – but dose 1 and dose 2 each use a different adenovirus, which gives the vaccine two different opportunities to trigger the immune system.

The US vaccine Novavax uses another old-school tactic in a new way: it’s a protein subunit vaccine. It contains whole SARS-COV-2 spike proteins, so the body doesn’t have to make them. These proteins have been grown in lab-based insect cells (originally taken from the fall armyworm moth), then purified.

Without a virus to support them, SARS-COV-2 spike proteins fall apart in the vaccine vial or in the body, before the immune system has time to recognise them. But Novavax has figured out a way to keep them stable: when mixed with polysorbate 80, the proteins arrange themselves into “rosettes” the size of nanometres, with polysorbate 80 at the core keeping them together. These nanoparticles then last long enough for our immune system to find them.