The Food and Drug Administration is alerting Americans to the potential dangers of at-home COVID-19 tests after receiving reports of people egregiously misusing them, resulting in injuries.

In a safety communication released Friday, the FDA said it had received reports of injuries after people used the kits' liquid test solution as eye drops or stuck the solution up their noses. "The liquid test solution is not supposed to touch your body," the FDA wrote sternly. The agency also reported that some children had been injured after putting test components in their mouths and swallowing the solution.

"The liquid solutions may include chemical ingredients, such as sodium azide, that help the test work properly or act as preservatives," the FDA wrote. "The test chemicals can be irritating or toxic if they get on your skin, nose, or eyes or if they are swallowed."

Vaccine-makers Moderna and Pfizer have now both submitted requests for the US Food and Drug Administration to authorize fourth doses—second boosters—of their COVID-19 vaccines.

Pfizer, along with vaccine partner BioNTech, announced Tuesday that they had asked the FDA to authorize fourth doses for adults age 65 and above. The move followed days of Pfizer CEO Albert Bourla saying in press interviews that a fourth shot is "necessary" for everyone.

Late Thursday, Moderna announced that it, too, had asked the FDA to authorize fourth doses—for all adults. Moderna addressed the broader request in its announcement, saying it’s intended to "provide flexibility" for the FDA and the Centers for Disease Control and Prevention to decide for themselves who should get a fourth dose—whether it's specific age groups and/or groups with higher risks of disease.

The outlook for the submissions is murky. On one hand, real-world data indicates that protection from three doses is waning against omicron, particularly against infection. And although cases in the US are in decline for now, a yet-more-transmissible version of omicron—BA.2—continues to increase in prevalence. It's now estimated to account for 23 percent of cases in the US, furthering its steady progress in usurping the initial omicron variant, BA.1. The rise of BA.2, coupled with widespread relaxation of mitigation efforts, such as mask wearing and distancing, have many experts anticipating another rise in cases, as is currently happening in many countries in Europe. Already, SARS-CoV-2 levels in US wastewater are rising, signaling an early warning of increasing transmission. Together, this all makes an argument for use of a fourth dose now, at least in vulnerable populations.

But, on the other hand, it's unclear how much a fourth dose would help to prevent infections and how long such gains would last. Though vaccine effectiveness does appear to be waning across the board, protection from hospitalization and death remains strong. (Effectiveness against hospitalization four months after a third dose fell from 91 percent to 78 percent, CDC data found recently.) And much of the data on the effectiveness of fourth doses comes from Israel, where fourth boosters have been offered to several groups—including people age 60 and above, as well as health workers and people at high risk of exposure or disease—but only for a short period of time so far.

In one study, carried out with the help of the Israeli Ministry of Health, Israeli researchers analyzed health records of more than 1.1 million people age 60 and over who were eligible for a fourth dose amid the omicron wave. People with a fourth dose were two times less likely to be infected and around four times less likely to have severe COVID-19 compared with people who had only three shots, the analysis found. However, fourth doses were only recently offered, and the study period was short. The researchers weren't able to look at effectiveness past the first 23 days after a fourth dose. The study was posted online on a pre-print server and has not yet been peer-reviewed.

In another study published Wednesday in The New England Journal of Medicine, fourth doses seemed less useful against omicron. Researchers examined data on 1,050 Israeli health care workers who were eligible for fourth shots. Of those, 154 received a fourth dose of the Pfizer vaccine and 120 received a fourth dose of the Moderna vaccine. Overall, the fourth doses appeared safe and bolstered waning antibody levels compared with those in matched controls. However, effectiveness against infection was modest at best. While 25 percent of health workers in the control group were infected, so were 18 percent of people who got a fourth dose of the Pfizer vaccine and 21 percent of people who got a fourth dose of the Moderna vaccine.

Biden Administration Plans to Offer Second Booster Shots to Those 50 and Up

After fraught discussions, officials decided that another shot might save thousands of lives if a new coronavirus wave hit before the fall. The F.D.A. could authorize the boosters next week.

WASHINGTON — The Biden administration is planning to give Americans age 50 or older the option of a second booster of the Pfizer-BioNTech or Moderna coronavirus vaccine without recommending outright that they get one, according to several people familiar with the plan.

Major uncertainties have complicated the decision, including how long the protection from a second booster would last, how to explain the plan to the public and even whether the overall goal is to shield Americans from severe disease or from less serious infections as well, since they could lead to long Covid.

Much depends on when the next wave of Covid infections will hit, and how hard. Should the nation be hit by a virulent surge in the next few months, offering a second booster now for older Americans could arguably save thousands of lives and prevent tens of thousands of hospitalizations.

But if no major wave hits until the fall, extra shots now could turn out to be a questionable intervention that wastes vaccine doses, deepens vaccination fatigue and sows doubt about the government’s strategy. The highly contagious Omicron subvariant BA.2 is helping to drive another surge of coronavirus cases in Europe and is responsible for about a third of new cases in the United States, but health officials have said they do not anticipate a major surge caused by the subvariant.