COVID-19: the Emergence and Growth of JN.1 Variant in the United States


The landscape of the COVID-19 pandemic is ever-evolving, with new variants constantly emerging. One such variant that has recently come into focus is JN.1. In this article, we will delve into the history, impact, and projections surrounding JN.1, shedding light on its emergence, spread, and potential implications for public health.

  • Background on Variants and Spread: The virus responsible for COVID-19 undergoes continuous changes, leading to the emergence of new variants. Variants may exhibit increased transmissibility or evasion of the immune system, impacting their prevalence. The Centers for Disease Control and Prevention (CDC) projects that JN.1 comprises an estimated 15–29% of circulating SARS-CoV-2 viruses in the United States as of December 8, 2023.
  • Historical Context and Relation to BA.2.86: JN.1 is closely related to the previously tracked variant BA.2.86, with only a single change in the spike protein differentiating the two. The detection of JN.1 in the United States dates back to September 2023, initially constituting less than 0.1% of SARS-CoV-2 viruses by the end of October. It was initially grouped with BA.2.86 on the COVID Data Tracker.
  • Impact and Transmission: The rapid growth of JN.1 raises concerns about its potential increased transmissibility or immune evasion. However, current data indicate no evidence of increased severity or heightened public health risks compared to other circulating variants. Updated COVID-19 vaccines are expected to enhance protection against JN.1, similar to their efficacy against other variants.
  • COVID-19 Activity and Monitoring: The surge in JN.1’s prevalence coincides with a general increase in COVID-19 activity in the United States. The CDC emphasizes the need for continued monitoring to understand the variant’s contribution to the ongoing surge. JN.1’s potential role in the observed patterns will be closely scrutinized through December and beyond.
  • Symptoms and Variability: At present, it remains uncertain whether JN.1 infection results in different symptoms compared to other variants. Symptoms of COVID-19 typically exhibit similarities across variants, with the severity often influenced by an individual’s immunity and overall health.
  • Projections and Nowcast: On December 8, 2023, the CDC introduced JN.1 separately on the SARS-CoV-2 Nowcast. In the latest weighted estimates, JN.1 comprised approximately 3.5% of U.S. sequences, with a confidence interval ranging from 2.4% to 5.0%. This marked a significant increase from the period before, where JN.1 constituted less than 1% of sequences.
  • Vaccine Efficacy and Laboratory Data: Early laboratory data suggests that individuals vaccinated against COVID-19 this year exhibit reduced susceptibility to JN.1. CDC’s Nowcast projections anticipate JN.1 to constitute between 15-29% of currently circulating variants in the United States as of December 8, 2023, with a best estimate of around 21%.
  • Future Considerations: As COVID-19 activity is expected to rise in the coming month, the importance of updated vaccines is emphasized to combat JN.1 and other variants. The CDC commits to ongoing surveillance, working collaboratively with global partners to understand variant spread and response to interventions.

Current Vaccination Trends Among Children: Insights from the National Immunization Survey

As the landscape of vaccination evolves, particularly concerning COVID-19, influenza, and RSV, the National Immunization Survey (NIS) plays a crucial role in providing up-to-date information on vaccination trends among children.

This chapter delves into the latest findings from the NIS, emphasizing the importance of vaccination and highlighting the trends observed as of December 1st, 2023.

  • Data Source Transition: The COVID-19 Public Health Emergency (PHE) prompted comprehensive tracking of COVID-19 vaccine administration by the Centers for Disease Control and Prevention (CDC). However, with the conclusion of the PHE, the reliance on survey responses has become paramount, as it now serves as the primary source for tracking vaccination data for COVID-19, influenza, and RSV among children.
  • Vaccination Trends Update: The most recent NIS update indicates a marginal increase in the percentage of the population reporting receipt of COVID-19, influenza, and RSV vaccines for both children and adults compared to the previous week. However, these rates remain relatively low. The percentage of children reporting receipt of the updated 2023-24 COVID-19 vaccine is 6.9% (95% confidence interval: 6.0-7.9), while adults 18 and older report a rate of 16.0% (15.3-16.7). Notably, among adults aged 65 and above, the vaccination rate is 33.3% (31.2-35.3).
  • Influenza Vaccination Rates: In terms of influenza vaccination, the data show that 38.2% (95% confidence interval: 36.9-39.5) of children and 38.7% (37.6-39.8) of adults aged 18 and above have received the flu vaccine. Among the older demographic (65+), a higher percentage is observed, with 62.2% (59.7-64.7) reporting receipt of the influenza vaccine.
  • RSV Vaccination Among Adults 60+: The report includes data on respiratory syncytial virus (RSV) vaccination, with 14.8% (13.6-15.9) of adults aged 60 and above reporting receiving the RSV vaccine.
  • Report Date: The findings were reported on Friday, December 1st, 2023, reflecting the most recent trends in vaccination coverage.
  • CDC Recommendations: The CDC reiterates its recommendation for all individuals aged 6 months and older to stay up to date on COVID-19 vaccines and receive the seasonal flu vaccine. Additionally, individuals aged 60 and older are advised to consult their healthcare providers regarding the appropriateness of RSV vaccination. For infants younger than 8 months entering their first RSV season, or born during it, the CDC recommends nirsevimab, a monoclonal antibody product.


As the nation navigates the complexities of ongoing vaccination efforts, the NIS serves as a critical tool for monitoring trends and guiding public health strategies. It is evident from the latest data that there is room for improvement in vaccination rates, particularly for COVID-19, influenza, and RSV, emphasizing the need for continued efforts to enhance vaccination coverage among children and the broader population.

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