The US Food and Drug Administration has discussed with vaccine-maker Novavax the need for an additional trial of its Covid-19 vaccine as a post-approval commitment, a source familiar with the matter told CNN.

Comments over the weekend by FDA chief Martin Makary suggest the agency views Novavax’s updated COVID shot as a “new product” requiring additional clinical study.

In addition, HHS Secretary Robert F. Kennedy Jr. addressed the delay in Novavax's approval in a CBS interview earlier this month, making it clear that it was a strategic decision based on the vaccine's mechanism of action, not an administrative delay.