Pfizer IncEarly data submitted by the company and BioNTech SE to US regulators showed that a third dose of their Covid-19 vaccine eight to nine months after the completion of the initial vaccination program produced higher levels of protective antibodies.

According to Monday's announcement, the two companies expect to have the results of a larger final phase of the trial soon, which will be submitted to the U.S. Food and Drug Administration, the European Drug Administration and other regulators.

Pfizer Inc said last month that based on early data, the company would apply to US regulators for emergency use authorization for its vaccine. Early data show that a third dose of the vaccine can significantly enhance immune protection against coronavirus and its variants, including Delta.

Now, the two companies are looking for another way to seek formal approval rather than emergency authorization for strengthening needles. Pfizer Inc and BioNTech said that after their initial application submitted in May was approved, they planned to seek permission for a third shot of vaccination for people aged 16 and over by supplementing the "application for permission for biological agents".

At 1:23 in New York time, Pfizer Inc's shares were basically flat in New York, while BioNTech's American depositary receipts fell 12%, extending the decline seen before the announcement.