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.

Federal regulators are asking Novavax to complete an additional randomized clinical trial on its Covid-19 vaccine after previously delaying approval, people familiar with the matter said, a request that could be so prohibitively expensive the company might not be able to fulfill it.

Federal regulators have asked Novavax to complete an additional clinical trial on its COVID-19 vaccine after previously delaying approval, the Wall Street Journal reported on Friday, citing people familiar with the matter.