The JN.1 variant of COVID-19 has rapidly spread since its detection in August 2023, becoming dominant in Australia and around the world. This has led to the biggest wave of infections seen in many jurisdictions in at least the past year. The World Health Organization (WHO) classified JN.1 as a “variant of interest” in December 2023 and emphasized the continuing global health threat posed by COVID-19.
What makes JN.1 significant is not only its pathogenicity but also what it reveals about COVID-19’s evolution. Unlike most variants, which accumulate a few mutations at a time, JN.1 emerged seemingly out of the blue with markedly different characteristics from previous strains. This has significant implications for disease and transmission. Despite the ongoing success of the steadily evolving omicron variants, JN.1’s distinctiveness and its wave of new infections have raised questions about whether it will be recognized as the next variant of concern by the WHO.
The story of JN.1 begins with its parent lineage, BA.2.86, which emerged around mid-2023 from an earlier omicron sub-variant. Chronic infections that linger for months or even years likely play a role in the emergence of these step-change variants. In chronically infected individuals, the virus silently tests and retains mutations that help it evade immunity and survive. For BA.2.86, this resulted in more than 30 mutations of the spike protein, which is crucial for the virus to attach to our cells.
The sheer volume of infections occurring globally provides fertile ground for major viral evolution. SARS-CoV-2, the virus that causes COVID-19, continues to mutate at a high rate. As a result, JN.1 itself is already mutating and evolving rapidly.
JN.1 stands out from other variants in two significant ways. Firstly, it evades immunity more effectively due to the more than 30 mutations in its spike protein. It has also acquired a new mutation, L455S, which further decreases the ability of antibodies to bind to the virus and prevent infection. Secondly, JN.1 enters and replicates in our cells differently from other variants. While laboratory studies have shown conflicting results, preliminary research suggests that JN.1’s replication characteristics align more closely with omicron lineages. Understanding these differences is crucial as they can affect disease severity and transmission.
Despite these unique features, evidence suggests that our adaptive immune system can still recognize and respond effectively to JN.1. Updated vaccines, tests, and treatments remain effective against this variant. However, JN.1’s greater transmission capacity has led to more illness and deaths simply because it infects more people.
The future trajectory of JN.1 remains uncertain. It is unclear whether it will evolve into a milder form of the virus or continue to pose a significant threat. What is certain is that we are experiencing a continuing epidemic with COVID-19, and waves of infection are likely to persist for the foreseeable future. This highlights the importance of comprehensive strategies to reduce transmission and mitigate the impacts of the virus.
Individuals are advised to continue taking active steps to protect themselves and those around them. Additionally, global surveillance and intensified research are crucial for better pandemic preparedness and an improved response to emerging threats. It is concerning that low- and middle-income countries are underrepresented in global surveillance efforts, and efforts should be made to address this blind spot.
In conclusion, the emergence of the JN.1 variant underscores the ongoing threat posed by COVID-19. It is a reminder that we need to rethink the risks of accepting wave after wave of infection and prioritize comprehensive strategies to combat the virus’s transmission and impacts.