US President Joe Biden received his updated Covid booster dose on Tuesday, as the country confronts a slow overall uptake of the new shot and faces a possible winter surge in cases and hospital admissions.
"The truth is, not enough people are getting [boosted]. We've got to change that so we can all have a safe and healthy holiday season," Mr Biden said before the injection.
US agencies last month approved bivalent Pfizer and Moderna booster shots that target both the original coronavirus and Omicron variants, and it was available for everyone shortly after.
More than 19.4 million people in the US over the age of 5 have received their updated booster dose, the most recent data from the US Centres for Disease Control and Prevention shows.
Because he was eligible due to his age, he had a second booster in March but was still infected with Covid in July.
The US president called on Congress to approve more than $22 billion in Covid funding, which his administration been requesting for months.
The White House Covid Response co-ordinator, Dr Ashish Jha, said on Tuesday that financing shortfalls have led to a pause in the government's free rapid home-testing programme and a depleted PPE stockpile for healthcare workers.
And investments in newer treatments or vaccines may be at risk without more money.
The coming winter poses several challenges apart from a lagging booster campaign.
Fewer people are testing for Covid-19 and US agencies are updating their Covid data platforms less frequently, which may leave only a murky picture of the virus's effects on the country as new subvariants emerge.
"We're seeing new subvariants, we're seeing an increase in cases of hospitalisations in Europe. So we know that there are some challenges ahead," Dr Jha said.
The spectre of a serious Covid surge looms while reports say the US flu season has started earlier than normal, and as child RSV infections are overwhelming paediatric hospitals.
More than 1 million people have died of Covid-19 in the US.