How Novavax is different from other coronavirus vaccines

The Novavax vaccine is called a subunit vaccine because it uses a portion of a virus to activate the immune system.

Scientists grow coronavirus spike proteins in the cells of fall armyworm moths inside giant bioreactors. (Insect cells are particularly good at making complex proteins such as those that make up the spikes.)

They mix in a detergent to create a spike-covered soap bubble that looks like the coronavirus. They also add an ingredient called an adjuvant that revs up the immune system so it will respond more forcefully.

Subunit vaccines take longer to produce than the newer types. A handful of cases of heart inflammation occurred during the Novavax trials, although it is unclear whether the vaccine caused the inflammation.

But Novavax has advantages. It stays stable longer under typical refrigeration, does not contain ingredients used in other vaccines that trigger allergies, and may appeal to people who prefer an older, more familiar technology. Some flu, hepatitis B and shingles vaccines are subunit vaccines.