COVID Variant JN.1 Dominates U.S. Cases, CDC Reports

Trends and Insights

The JN.1 variant of COVID-19 is now responsible for an estimated 93.1% of total infections in the United States, according to the Centers for Disease Control and Prevention. This highly mutated strain has rapidly become the dominant cause of new cases, with a significant impact on the spread of the virus across the country.

The CDC's latest biweekly report highlights the overwhelming prevalence of the JN.1 variant, coinciding with a notable decline in key indicators of COVID-19 spread in other areas. The agency's assessment reveals that the South is the only region where wastewater data reflects an increase in virus levels in recent weeks, while most parts of the country are experiencing a substantial decrease in newly diagnosed COVID-19 cases in emergency rooms. However, some states in the South appear to have reached a plateau in case numbers.

Vaccine Effectiveness

In response to the JN.1 variant, the CDC has released new data from its pharmacy testing program, indicating that the updated COVID-19 vaccines have exhibited 49% effectiveness against symptomatic JN.1 infection among individuals who were vaccinated between two to four months prior. This data pertains to the period from September 2023 to January 2024, encompassing the XBB lineage variants and the emerging JN.1 strain.

Severity and Evolution

Amid concerns about the severity of the JN.1 variant, CDC officials have conveyed early signals from ongoing studies suggesting that the strain's impact is not more severe than previous variants. This represents a departure from previous statements asserting that there was "no evidence" indicating increased severity. The CDC's current estimates mark a significant shift, as the JN.1 variant previously accounted for less than half of infections in late December.

Global Context

The emergence of the JN.1 variant was first recorded in the global virus database GISAID in August, with initial cases identified in Iceland and Luxembourg. By September, the U.S. had confirmed at least 11 cases of this descendant of the BA.2.86 variant, raising concerns about its accelerated spread. While the World Health Organization designated JN.1 as a "variant of interest" in December due to its rapid ascent, U.S. health authorities have continued to classify the strain under its BA.2.86 parent.

Looking Ahead

As the JN.1 variant continues to shape the course of the pandemic, ongoing surveillance and analysis will be crucial in understanding its impact on public health. The CDC's comprehensive assessment provides valuable insights into the evolving landscape of COVID-19 in the United States, guiding efforts to mitigate the spread and address emerging challenges.

About the Author

Alexander Tin is a digital reporter for CBS News, based in the Washington, D.C. bureau, covering the federal response to infectious disease outbreaks, including COVID-19, and public health agencies under the Biden administration. Follow him on Twitter for the latest updates.