The new COVID-19 variant that scientists call JN.1 now makes up about 44.1% of COVID-19 cases across the country, the Centers for Disease Control and Prevention estimated Friday, marking another week of the fast-spreading variant's steep rise in the U.S.
The increase is more than two times larger than the 21.3% that the CDC now estimates the strain made up of infections for the week ending Dec. 9, after Thanksgiving.
Among regions with enough data reported from testing labs to produce these latest projections, the CDC estimates that JN.1's prevalence is largest in the Northeast region spanning New Jersey and New York, where the strain is 56.9% of cases in those states.
These new estimates come as other countries have also tracked a rapid ascent in JN.1's prevalence across recent weeks, prompting the World Health Organization to step up the strain's classification to "variant of interest" on Tuesday – its second highest tier.
Authorities have so far not reported different or more severe symptoms from JN.1 compared to previous strains.
Health officials are closely monitoring a new variant of COVID-19 known as JN.1, which has accumulated a significant number of mutations. This variant is believed to have inherited most of its mutations from its highly mutated parent BA.2.86. While BA.2.86 did not spread widely, JN.1's additional mutations have raised concerns about its transmissibility. The earliest cases of JN.1 in the United States were reported in September, and since then, it has become the fastest-growing variant in the CDC's estimates.
The CDC has not updated its variant classifications since September, when BA.2.86 was classified as a "variant being monitored." It is unclear whether JN.1 has received a classification from the CDC. The agency has not provided an update on JN.1 since a report on December 8.
Variants grouped under the BA.2.86 umbrella, which include JN.1, have also made up the largest share of variants detected from the CDC's airport testing program on arriving international travelers in recent weeks.
Effectiveness of COVID vaccines against JN.1
Data from early studies of the strain cited by the WHO in a risk evaluation this week also pointed to research suggesting JN.1 "displays a higher immune evasion" compared to its BA.2.86 parent, though not enough to prevent this season's COVID-19 vaccines from being effective.
This year's updated COVID-19 shots were targeted at the XBB.1.5 strains which drove a wave of infections earlier this year. A WHO panel earlier this month declined to call for an update to the vaccine's recipe, after mulling early data so far measuring the threat posed by JN.1.
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In a statement, a Novavax spokesperson said data from studies in mice and nonhuman primates showed its shot "induced cross-neutralization against JN.1" that was "similar" to other XBB strains.
A Pfizer spokesperson said that the company expects to have data in the coming weeks from tests of its vaccine against JN.1. A Moderna spokesperson did not immediately respond to a request for comment.
Concerns Rise Over New COVID-19 Variant
Health authorities are closely monitoring a new variant of COVID-19, known as JN.1, amid concerns that it could pose a significant threat to vaccine protection. Dr. Jeanne Marrazzo, head of the National Institute of Allergy and Infectious Diseases, expressed the possibility of a "quantum leap" in the erosion of vaccine protection. She emphasized the need for swift action if this were to occur.
The World Health Organization (WHO) has also been closely monitoring the new strain, looking at key indicators such as hospitalizations and deaths. Early data from Belgium and Singapore suggest that JN.1 may have similar or reduced hospitalization risks compared to other strains.
However, the WHO has not disclosed further details about these preliminary findings, stating that they were shared with the organization's experts before publication in a journal.
According to data from the Centers for Disease Control and Prevention (CDC), there has been a rise in COVID-19 emergency department visits and hospitalizations. However, these trends are not currently exceeding what was seen during previous winter waves.
It is important to note that the current trends are still far below the record surge experienced during the winter of 2021-2022, when the original Omicron variants spread across the United States during the Christmas and New Year's holidays.
