The COVID-19 vaccine developed by Novavax is being delayed again, as the Maryland-based company on Monday blamed shortages on production materials.

Novavax said it expects to seek regulatory authorization for its shot in the United States, Britain and Europe before the end of September, rather than the end of June. It also pushed back its timetable for reaching full production of 150 million doses a month to the fourth quarter of 2021 — it had targeted the third quarter.

While the announcement is not the first delay for the Novavax two-shot vaccine, Chief Executive Stanley Erck said Monday that it now appears the company has overcome “nearly all of the major challenges” it has faced in manufacturing the shots and that “we can clearly see the light at the end of the tunnel.”

Erck, however, said Novavax is still running into shortages of materials such as 2,000-liter bags, purification filters and substances that help grow proteins used in the vaccine. 

With three vaccines already on the market and demand declining in the U.S., Novavax’s latest delay is more of a setback for the global effort to combat COVID-19, as many poorer countries have extremely low vaccination rates.

Novavax has produced 30 million to 40 million doses of its vaccine to date, Erck said. The company has committed 1.1 billion shots to the COVAX international vaccine sharing program as well as an additional 200 million doses to countries around the world.

In March, Novavax, which has never brought a vaccine to market, announced that preliminary data from its clinical trial in the United Kingdom showed its vaccine was 96% effective against the original COVID-19 strain and 86% effective against the variant first detected in Britain.