The United States on Monday approved Covid vaccines with formulations that more closely target currently circulating variants, as infections are once more on the rise.

The new approvals relate to updated vaccines produced by Moderna and Pfizer that correspond to an Omicron sublineage. The Food and Drug Administration (FDA) concluded that the benefits of receiving the shots outweighs the risk for those aged six months and up.

"Vaccination remains critical to public health and continued protection against serious consequences of COVID-19, including hospitalization and death," senior FDA official Peter Marks said.

Both companies released statements saying they expect their vaccines to be widely available in pharmacies and clinics within the coming days.

A panel convened by the Centers for Disease Control and Prevention will meet tomorrow to offer clinical recommendations about who should receive the updated vaccines.

However, President Joe Biden's administration has consistently pushed for annual Covid boosters for most Americans and it is expected the CDC will offer similar guidance.

That policy would be at odds with much of Europe, where boosters are generally recommended for the elderly or those at higher risk because of underlying medical conditions.

This is the case in the United Kingdom, France and Germany, for example.

Moderna and Pfizers' updated vaccines target variant XBB.1.5, which has already largely faded from circulation in the United States. But it holds up well against newer strains such as EG.5 and BA.2.86, said the FDA.

Although the WHO and the United States ended their public health declarations of emergency in May, Americans should still be able to receive the new vaccines for free via private insurance and government subsidized programs.

- Vaccines for whom? -

Experts have mixed opinions about how widely the new shots should be targeted.

"I believe that every American is better off getting a Covid booster this fall," Ashish Jha, who served as the White House Covid response coordinator, told AFP.

"People at the highest risk will benefit the most, but even lower-risk individuals do better if they are vaccinated."

But others would prefer the United States follow a more targeted strategy given the differing risk-benefit profiles across age groups.

"I believe boosters should be given to only particular at-risk groups (like older individuals) since a one-size-fits all approach can decrease trust in public health," said Monica Gandhi of the University of California, San Francisco.

Both the Pfizer and Moderna shots, which are based on mRNA technology, carry rare risks of heart inflammation, especially among young men, for example.

Covid took a horrific toll across the world, killing nearly seven million people, according to the World Health Organization (WHO). But thanks to vaccines, prior immunity and better treatments, the virus has become far more manageable.

In the United States, excess deaths -- the total number of people dying for any given cause -- has been nearly normal since springtime.