Moderna has sought emergency use authorisation with US health regulators for a second COVID-19 booster shot for all adults, as a surge in cases in some parts of the world fuels fears of another wave of the pandemic.

The company's request comes days after Pfizer and its German partner BioNTech SE filed an application with the US Food and Drug Administration, seeking emergency use authorisation for a second booster shot of their COVID-19 vaccine for people aged 65 and older.

Moderna said its request covered all adults over the age of 18 so US Centers for Disease Control and Prevention and healthcare providers could determine the appropriate use of an additional booster dose of its vaccine, including "for those at higher risk of COVID-19 due to age or comorbidities".

Moderna, without specifically commenting on the effectiveness of a fourth shot, said its submission was partly based on data recently published in the United States and Israel following the emergence of the Omicron variant.

US health officials, including top infectious disease expert Dr Anthony Fauci, have raised the prospect of a fourth shot, especially for older people and to prepare for the possibility of another surge in cases.

The news was first reported by the New York Times.