Updated COVID Vaccine Offers Strong Protection Against Dominant JN.1 Variant

The JN.1 COVID-19 variant now makes up more than 93 percent of cases, according to latest tracking from the Centers for Disease Control and Prevention (CDC). That’s a major leap from two months ago when this highly mutated version of the virus accounted for just 1 in 5 infections.

Although evidence suggests that JN.1 is either highly transmissible or better at evading our immune systems, as of February 2, key indicators from the CDC are showing decreasing levels of COVID activity nationally, with hospitalizations and test positivity trending down in recent weeks.

A CDC study published at the beginning of this month suggests that the newest COVID-19 vaccine may be playing a role in keeping the JN.1 variant from having a more severe impact on public health.

Latest Shot Defends Against Both Severe and Mild Infection

Based on an analysis of more than 9,000 individuals who were tested for COVID-19 at participating CVS Pharmacy and Walgreen pharmacies between September 21, 2023, and January 14, 2024, researchers found that those who’d received the updated COVID-19 vaccine had about 54 percent increased protection against symptomatic JN.1 infection compared with those who hadn’t received the updated vaccine.

“The results here show a high rate of protection against symptomatic COVID-19 disease if you receive the 2023–24 updated COVID-19 vaccine,” says Mark Mulligan, MD, director of the NYU Langone Vaccine Center in New York City. “We are still in the middle of the respiratory virus season, so it is definitely not too late to get the updated shot.”

The Rise of JN.1. Did Not Diminish the Effectiveness of the Vaccine

In September 2023, the CDC recommended that everyone 6 months and older get the updated vaccine to protect against the potentially serious outcomes of COVID-19 illness. The shot was specifically formulated to target the widely circulating omicron XBB.1.5 subvariant.

As JN.1 gained traction, it was uncertain how effective this vaccine would be against it. Although JN.1 is also in the omicron family, this variant has more than 30 mutations in the spike protein compared with XBB.1.5, per the CDC. Spike proteins allow the virus to enter healthy cells, causing the infection.

This latest CDC research, however, revealed that the updated shot provided similar levels of protection against both the XBB lineage variants and the JN.1 variant.

“Enough similarity remains between the XBB.1.5 variant and the JN.1 variant that the immune systems of persons who have been vaccinated can recognize the new variant and reduce the severity of infection, if not prevent symptomatic infection,” says Robert H. Hopkins Jr., MD, medical director of the National Foundation for Infectious Diseases (NFID).

The study authors note that the updated COVID-19 vaccines have only been available since mid-September, so estimates regarding effectiveness include data from just four months.

The Updated COVID-19 Vaccine Will Eventually Become Less Protective

Because protection against COVID-19 from earlier versions of the vaccine decreased over several months after vaccination, the CDC expects that protection from the updated vaccine will also decline over time.

“Since we have seen waning repeatedly with earlier vaccines, we do expect some waning to occur,” says Dr. Mulligan.

He foresees that we will need another updated vaccine formulation as the virus continues to circulate and evolve.

“I anticipate that we will have a recommendation for an annual COVID-19 vaccine in the same way that we have an annual flu shot — updated each year to boost immunity and better match the circulating viruses,” says Mulligan.

Dr. Hopkins adds that for now, it is reassuring that the current vaccine remains effective in protecting against symptomatic infection.

“I would encourage anyone who has not yet received a 2023–2024 COVID-19 vaccine to get vaccinated as soon as possible,” he says. “My recommendation is even stronger based on this new data.”

As of February 2, only about 22 percent of people 18 and older have received the updated vaccine, according to CDC data. For adults 65 and older, that figure is 41 percent. Roughly 12 percent of children have gotten the updated shot.

The CDC stresses that the vaccination not only remains the best protection against COVID-related hospitalization and death, but it also reduces your chance of developing long COVID, which can develop during or following acute infection and last for an extended duration.

For help finding COVID-19 vaccines, visit Vaccines.gov.