(Reuters) -The U.S. government has awarded Moderna $590 million to advance the development of its bird flu vaccine, as the country doubles down on efforts to tackle increasing infections in humans.

This is in addition to $176 million awarded last year to complete late-stage development and testing of a pre-pandemic mRNA-based vaccine against the H5N1 avian influenza.

The funding will also support the expansion of clinical studies for up to five additional subtypes of pandemic influenza, Moderna said on Friday.

Moderna is testing the experimental shot, mRNA-1018, against several strains of the virus - including the currently circulating H5N1 variant.

The drugmaker said it is preparing to advance mRNA-1018 into late-stage trials based on preliminary data from an early-to-mid stage study and plans to present the data at an upcoming medical meeting.

The award was made through the Rapid Response Partnership Vehicle (RRPV) Consortium with funding from the U.S. Biomedical Advanced Research and Development Authority.

Nearly 70 people in the U.S., most of them farmworkers, have contracted bird flu since April, as the virus has circulated among poultry flocks and dairy herds.

Most infections in humans have been mild, but one fatality was reported in Louisiana last week.

The risk to the general public from bird flu is low, and there has been no further evidence of person to person spread, according to the U.S. Centers for Disease Control and Prevention.