Margins for the vaccine could also be a concern. Novavax's vaccine is based on subunits – essentially using a fragment of the virus – and the manufacturing process is apparently more complex compared to the method used in messenger RNA vaccines including Moderna's. This could potentially make the Novavax vaccine more expensive to manufacture. Based on a supply agreement with the U.S. government, the Novavax vaccine will be priced at about $16 per dose, below the $19.50 for Pfizer's vaccine and as much as $37 per dose for Moderna's.