Covid booster shots that target hyper-transmissible omicron variants will be available from September, the Biden administration has announced.
The reformulated vaccines appear to be effective against the BA.5 and BA.4 strains that now make up more than 90 per cent of cases in the United States, CDC figures show.
On Friday, the Department of Health and Human Services (HHS) announced the purchase of 66 million doses of the Moderna vaccine that would be available over the fall and winter.
It came after the purchase of 105 million Pfizer vaccine booster doses last week.
“We must stay vigilant in our fight against Covid-19 and continue to expand Americans’ access to the best vaccines and treatments,” HHS Secretary Xavier Becerra said in a statement.
“As we look to the fall and winter, we’re doing just that — ensuring Americans have the tools they need to stay safe and help keep our nation moving forward.”
The US is experiencing a sixth wave of Covid cases fuelled by the highly contagious BA.5 and BA.4 omicron subvariants, with the CDC recording a rolling 7-day average of 126,272 cases on 27 July.
President Joe Biden last week contracted a mild case of the BA.5 sub variant, his doctors said.
Existing vaccines are effective at minimising the risks of severe illness, hospitalisation and death, but the BA.5 variant has evolved to bypass the effects of the doses and immunity from past infection.
The HHS said should the booster shots pass receive authorisation, they would seek additional funding from Congress to ensure there were enough shots for every American who wanted one.