(CNN) The White House's Covid-19 response team sent a clear message to the nation this week on the spread of the Omicron subvariant BA.5 and the importance of second vaccine booster doses for adults over the age of 50.
"If you have not gotten a vaccine shot in the year 2022, if you have not gotten one this year, please go get another vaccine shot," response coordinator Dr. Ashish Jha said Tuesday. "It could save your life."
Second boosters have been authorized for US adults 50 and up, as well as certain people with weakened immune systems, since March. But for anyone under the age of 50, only one booster is authorized.
The officials had less to offer younger adults at the briefing, other than to say that the US Food and Drug Administration is considering second boosters for this age group.
As of the end of June, adults under age 50 had the highest rates of Covid-19 cases compared to other age groups, according to preliminary data from the US Centers for Disease Control and Prevention.
"I know that the FDA is considering this, looking at it," Jha said Tuesday of second boosters for younger adults. "And I know CDC scientists are thinking about this and looking at the data, as well. The decision is purely up to them."
Dr. Anthony Fauci, director of the National institute of Allergy and Infectious Diseases, stressed Wednesday in an appearance on CNN that the idea was being "actively considered." But beyond that, he made no promises, saying the OK on expanding eligibility had to come from the FDA.
In the meantime, Americans under 50 are watching the lightning spread of the BA.5 subvariant and wondering about their own protection.
"It's frustrating and, frankly, scary," said Jennifer O'Neill, 42, who lives in Boston with her 74-year-old mother. O'Neill says she's been waiting on the government to expand eligibility for boosters to younger adults and doesn't understand why it hasn't happened yet.
Both O'Neill and her mom have had all the boosters they're eligible for, but O'Neilll's last shot was around Thanksgiving. She believes that booster protected her during their first family dinner in two years. Four of the 10 guests at Thanksgiving dinner caught Covid-19, but O'Neill and her mom didn't get sick.
"I know it's not the same variant. I know in my head it won't prevent transmission entirely, but I am just so concerned with her not getting sick that I'll do whatever I can," O'Neill said of her mother, whose age puts her at high risk of more severe illness. "And it frustrates me that I can't because of eight years."
About 139 million adults in the US are between 18 and 50, according to Census data. Many of them followed public health guidance and got boosters as soon as they became eligible last fall, when the original Omicron strain was tearing across the country.
Data from the UK shows that the effectiveness of booster shots against symptomatic disease caused by the Omicron variant is higher than 60% starting about four weeks after a third dose. After eight weeks, though, it starts to decline, and by five months post-booster, people have almost no protection against symptomatic infections.
So whatever protection young adults had against infection from last fall's booster is probably long gone.
That may be disheartening, but it's also not really what the vaccines were designed to do, says Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical Center in Nashville, Tennessee.
If protection against Covid-19 is your goal, you may be better served by using a combination of other tools, like wearing high-quality masks, making sure you're spending time in well-ventilated spaces with clean air and, if you have the luxury, being choosy about your social contact.
"These vaccines don't prevent mild infection," Shaffner said, and they don't keep you from infecting others. "These are personal protection vaccines, rather than vaccines that prevent transmission in any substantial way."
The vaccines and boosters continue to offer stronger protection against Covid-19 infections that are severe enough to need hospital or ICU care, or that might be fatal.
However, this protection is also slipping over time.
For adults ages 18 to 64, the effectiveness of a booster against Covid-19 hospitalization peaks around 82.4%, but it drops to about 53.6% about four months after the third shot, according to UK data. For adults over the age of 65, boosters are initially about 86% effective at keeping people out of the hospital, but that protection drops to 77% after roughly four months.
Protection against death from Covid-19 falls to about 48% roughly six months after a second vaccine dose in adults 50 and older. Boosters initially restore that protection to about 94%, but that falls to 88% after 10 weeks or so, according to UK data. There was comparable data available for younger adults.
In the US, CDC data presented at the White House Covid-19 briefing on Tuesday shows that adults over the age of 50 who've had one booster dose had four times the risk of dying from Covid-19 compared with those who've had at least two booster doses.
Schaffner says people who are under 50 and generally healthy are still in good shape when it comes to severe outcomes from Covid-19.
But, he says, if you are under 50 and have an underlying health condition like heart disease, lung disease or diabetes, you should ask for a second booster even if you're not officially eligible.
"People are not usually quizzed too thoroughly," Shaffner said. "I would just come up and say 'Hi, I've got bad diabetes' or 'I have underlying heart disease' and stuff like that, and at least in our neck of the woods, you'll be able to get a vaccine."
O'Neill tried to get a fourth shot. She didn't lie; she has asthma and pleaded her case at two pharmacies, but they pointed her to a narrow list of conditions that qualify people for additional doses if they're under 50.
"I'm in Massachusetts, but the two pharmacists were very adamant, like I could get in trouble if I don't follow guidelines," she said.
Her friends have told her to lie, but she doesn't feel comfortable doing that. "I want to follow protocol," she said.
She's frustrated by what she sees as mixed messaging from the Biden administration on Covid-19.
"It's like 'Get out! Get back to normal!' OK. But I'm only comfortable actually getting out if I feel like I'm fully protected, and I know that the booster won't prevent transmission, it would just make me feel much more safe," she said. So she'll continue to limit her activities until she can get a booster.
With or without vaccines, Jha said, there are things people can do to protect themselves if they do fall ill, including seeking treatment.
"We have highly effective treatments that work against BA.5, including Paxlovid. This is an oral antiviral that reduces the risk of hospitalizations and death by 90%," he said.
He added that the US has bought more of these pills than any other country, and they are now available at 41,000 locations nationwide.
"If you test positive in the days and weeks ahead, please consult your health care provider about your eligibility for treatment," Jha said.