The U.S. wave is also riding at least one subvariant, BA.2.12.1, that seems to be able to reinfect people who were previously infected with the original Omicron strains (BA.1 and BA.1.1) just months ago. As of the week ending May 14, the CDC estimated that 47.5 percent of new U.S. COVID infections were from the BA.2.12.1 variant, which means the next round of data will likely indicate the subvariant has become the dominant COVID strain in the country, beating out BA.2, which had itself become dominant by the end of March. And the Omicron subvariants, each with their own unique advantageous mutations, are still coming: BA.4 and BA.5 are circulating in the U.S. as well; it remains to be seen if they will be more dangerous than BA.2.12.1.

Furthermore, thanks to waning immunity and low booster uptake, 60 percent of American seniors may now lack adequate protection against severe illness from COVID-19, according to CDC director Rochelle Walensky. Last week, she highlighted in a public meeting that there has been “a steep and substantial increase in hospitalizations for older Americans”— including a 25 percent rise among people 70 and older from the previous week. She also noted that just 43 percent of Americans 65 and older have received a dose of COVID vaccine in the past six months. Among seniors (and all U.S. demographics), the uptake of booster shots — which provide significant additional protection from severe illness and death — trails other comparable nations by a significant margin. Half of the unboosted Americans surveyed earlier this year by the Kaiser Family Foundation said they would either never get boosted, or only would if it was required.

There is currently no timetable for when new vaccines tailored to target the Omicron lineage may become available in the U.S., though there is at least some ongoing debate about how necessary they are in the near term.