Variants Happen

Summary

What CDC knows

The SARS-CoV-2 virus, which causes COVID-19, is constantly changing and new variants continue to emerge. A variant is a change in the virus. A new variant may infect people more easily, spread faster, or cause people to get sicker. Nevertheless, nearly all the SARS-CoV-2 variants currently circulating in the United States are closely related to the variant used for the updated 2023-2024 COVID-19 vaccines. This means that the updated vaccines should work well against currently circulating variants and continue to be the best way to protect yourself and others against severe disease.

What CDC is doing

CDC uses multiple systems to understand which SARS-CoV-2 viruses are circulating in communities, where they are circulating, and whether they are likely to contribute to surges in infection or serious illness. CDC then communicates these findings to the public.

The SARS-CoV-2 virus has many variants

Viruses are constantly changing over time. These changes – or variants – happen when viruses infect cells and begin to reproduce, and some of the resulting copies contain errors. Sometimes these changes enable the new variant to spread more quickly or effectively. In this case, that new variant may become more common relative to other variants that are circulating.

Because these viral changes continue to happen, CDC is constantly tracking their emergence and spread and closely studying new variants. Our process begins with genomic surveillance. CDC works with partners in the United States and around the world to track changes to the SARS-CoV-2 virus and publish those findings. CDC recently published two new reports describing how multiple types of genomic surveillance were used to track a new variant in August 2023 – Early Detection and Surveillance of the SARS-CoV-2 Variant BA.2.86 and Notes from the Field: Early Identification of the SARS-CoV-2 Omicron BA.2.86 Variant by the Traveler-Based Genomic Surveillance Program. CDC also works to understand how these changes might affect how the virus spreads, as well as how it responds to vaccines and treatments.

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Some recent variants have more changes than others

Occasionally a variant appears that is very different from previous variants, much like Omicron when it was first detected. In these cases, it's not always clear right away whether these very different changes will affect how the virus spreads or its health impact. For example, when scientists first identified the BA.2.86 variant in August 2023, they found that it appeared to be very different from other recently identified variants. This raised concerns that this variant might be more likely to spread and infect people, even people with immunity from vaccines and previous infections. However, later scientific data showed that the BA.2.86 variant has not evaded our immunity or spread quickly.

What about JN.1?

We are learning about a new variant called JN.1. JN.1 was first detected in September 2023 in the United States and has been detected in 11 other countries. With this limited information, it is too early to tell whether it will spread more widely. Neither JN.1 nor BA.2.86 is common in the United States right now. In fact, JN.1 has been detected so rarely that it makes up fewer than 0.1 percent of SARS-CoV-2 viruses.

Even though BA.2.86 and JN.1 sound very different because of the way variants are named, there is only a single change between JN.1 and BA.2.86 in the spike protein. The spike protein – called a "spike" because it looks like tiny spikes on the virus' surface – plays a crucial role in helping the virus infect people. Because of this, the spike protein is also the part of a virus that vaccines target, meaning vaccines should work against JN.1 and BA.2.86 similarly. For example, initial scientific data show that the updated 2023-2024 COVID-19 vaccines help our immune systems block BA.2.86. We expect JN.1 will be similar. We also expect treatments and testing to remain effective based on analysis conducted by the SARS-CoV-2 Interagency Group (a group of scientific experts representing many government agencies).

What does this mean for me?

While new variants like BA.2.86 and JN.1 attract attention, right now, 99 percent of SARS-CoV-2 variants are part of the XBB group of the Omicron variant, which is what this year's updated vaccines are based on. CDC is continuing to track the spread and impact of BA.2.86 and JN.1, as well as other variants as they come and go.

For as long as we have COVID-19, we'll have new variants. Nearly all represent relatively small changes compared with previous variants. CDC and other agencies monitor for impacts of new variants on vaccines, tests, and treatments, and will alert the public quickly if anything concerning is detected. Most of the time, new variants make little to no impact.

Regardless of the variant, all SARS-CoV-2 viruses spread the same way. So it's important to protect yourself and others by staying up to date with COVID-19 vaccines, improving ventilation and staying home when you're sick.