WASHINGTON (AFP) - The United States on Monday (Aug 2) hit US President Joe Biden's goal of administering 70 per cent of adults with at least one dose of a Covid-19 vaccine, almost a month after the July 4 target date.

The Centers for Disease Control and Prevention's website showed that 60.6 per cent of adults, and 49.7 per cent of the total population, have now been fully vaccinated.

The Biden administration initially targeted the country's Independence Day to hit the goal and declare victory over the worst of the pandemic.

But falling vaccination rates, particularly in politically conservative regions in the South and Midwest, and among groups like younger people, those with lower income and racial minorities, meant the objective was missed.

Recent weeks however have seen an uptick in the vaccination rate in the regions hit hardest by the latest Covid-19 wave, which is being driven by the hyper-contagious Delta variant.

States such as Arkansas, Missouri, Louisiana, and Florida have all seen significant increases.

The national average of daily cases is currently higher than 60,000 and rising rapidly.

However, with 80 per cent of seniors fully vaccinated, hospitalisations and deaths are rising far slower than in previous waves.

While one dose of an mRNA vaccine by Pfizer or Moderna conferred strong protection against previously dominant variants, new peer-reviewed research highlights the need for two doses against the Delta variant.

Federal health authorities are also debating whether a third dose may be required for certain groups such as the immunocompromised.

The CDC has also reinstituted guidance for fully vaccinated people to wear masks indoors in high-risk areas, after a preliminary analysis suggested that people who have breakthrough cases of the Delta variant might be able to transmit the virus onward.