As the holiday season winds down and Covid-19 cases begin to rise, a variant called JN.1 has become the most common strain of the virus circulating throughout the United States.
JN.1, which emerged from the BA.2.86 variant and was first identified in the United States in September, accounted for 44 percent of Covid cases nationwide as of mid-December, up from about 7 percent in late November, according to data from the Centers for Disease Control and Prevention.
To some extent, this jump was expected. “Variants take some time to develop,” said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center. “Then they accelerate, they spread widely, and when they do that, after a few months, a new variant appears.”
JN.1’s momentum this month suggests it may be more easily transmitted or better at evading our immune systems than other variants currently circulating, according to a CDC report published on December 22. The agency said that Covid remains “a serious threat to public health,” especially for those who are always at high risk of serious illness, such as the elderly, infants, people with compromised immune system or chronic medical conditions and those who are pregnant.
As far as experts can tell, JN.1 doesn’t seem to cause severe illness in most other people, though a mild case can still make you feel “pretty miserable for three or four that day,” said Dr. Schaffner. Symptoms of JN.1 infection are similar to those caused by previous Covid variants, including cough, fever, body aches and fatigue.
To protect yourself against infection and serious illness, experts continue to recommend wearing masks, improving indoor ventilation if possible, staying home when sick and getting the latest Covid vaccine.
Preliminary research shows that the updated Covid vaccines released in September produce antibodies that are effective against JN.1, which is distantly related to the XBB.1.5 variant that the vaccines are designed to target. People may not develop as many antibodies to JN.1 as they would to XBB.1.5, but the levels should still reduce risk.
“For those recently infected or boosted, cross-protection against JN.1 should be decent, based on our laboratory studies,” said Dr. David Ho, a virologist at Columbia University who presided the research on JN.1 and Covid vaccines, released as a preprint paper in early December. Rapid tests also continue to be an important tool, and the CDC says tests on the market work well in detecting JN.1.
There are signs that Covid cases are creeping up again. Just under 26,000 were hospitalized due to Covid in the week of December 10, a 10 percent increase from about 23,000 hospitalizations the previous week. But Covid hospitalizations are still lower than during the peak of the first Omicron wave in January 2022, and so far are only about half as high as at the peak of the tripledemic last winter, when Covid-19, influenza and RSV cases all jumped at once.
It is too early to know if JN.1 is responsible for the increase in hospitalizations or if cases are increasing due to increased travel and large gatherings for Thanksgiving and the winter holidays.
“When people gather indoors in close proximity to each other, have parties and travel and so on, those are the types of circumstances where all respiratory viruses, including JN.1, are there are opportunities to spread,” said Dr. Schaffner. Covid in general also has seasonality, he added; Northern Hemisphere countries tend to see a dip in cases in the fall before infections and hospitalizations rise again in the winter.
JN.1 is likely to remain the dominant version of the coronavirus until spring, said Dr. Schaffner. He and other experts noted that while vaccines offer protection against this and other variants, uptake remains low, with only 18 percent of adults who have received the most recent shots. Experts say everyone should consider getting vaccinated, especially those over age 65, are immunocompromised, have health conditions that put them at higher risk of serious illness or are traveling to visit loved ones. in life that may be weak.
“Give yourself a New Year’s gift by getting this vaccine if you haven’t already,” said Dr. Schaffner.
