Novavax will delay submitting its COVID-19 vaccine for emergency use authorization until the fourth quarter of this year, the company announced Thursday.

The Maryland-based drug maker previously said it would seek authorization from the Food and Drug Administration in the third quarter.

Chief Executive Officer Stanley Erck said during an earnings call that the timeline is “hopefully early” in the fourth quarter.

The Novavax vaccine candidate offers potential for the U.S. to add another highly effective vaccine. In June, the company said its vaccine has an efficacy of 90 percent, on par with the effectiveness of the Pfizer-BioNTech and Moderna vaccines.

But the company struggled to scale up production, and has repeatedly delayed its expected submission date.

Still, Erck said the company remains on track to produce 100 million doses per month by the end of the third quarter of this year, and 150 million doses per month by the end of the fourth quarter.

The company said it has filed for regulatory authorization of its COVID-19 vaccine in India, Indonesia and the Philippines, and expects to file for World Health Organization’s (WHO) emergency use listing later this month. 

Once the vaccine is authorized by the WHO, it can be exported to countries that participate in the COVAX program.

Erck said the vaccine will be ready to ship upon authorization, though doses will likely be prioritized to low-and middle-income countries.

Separately, the company announced data from clinical trials showed that a booster dose of the vaccine candidate provided a fourfold increase in neutralizing antibody levels against the original “wild type” virus when given six months after an initial two-dose regimen.

Novavax said its data also showed that a booster dose could provide up to sixfold protection against the delta and other variants. Complete data from the study will be submitted to a peer review publication and posted to a preprint server, the company said.