We're having a COVID summer surge. Should you get the updated vaccines now?

The summer of 2024—the fifth since the COVID-19 pandemic began—is projected to be the biggest summer wave of COVID infections to date. 

Since early May, COVID infections have steadily increased in the United States, Europe, Singapore, New Zealand, and Australia. The U.S. Centers for Disease Control and Prevention estimates that COVID-19 infections are currently increasing in 25 states based on data from emergency department visits. However, hospitalizations and deaths from COVID remain at their lowest levels.

Now, the U.S. Food and Drug Administration has approved updated vaccines to protect against current variants of the virus.

This recent surge has been driven mainly by a new group of closely related Covid subvariants, known collectively as "FLiRT."

As the summer winds down, students across the U.S. will return to school. Traditionally, this also coincides with the season of respiratory viruses, such as flu, RSV, and increasingly COVID. 

"Not sure what will happen this fall and winter," says Kei Sato, a virologist at the University of Tokyo. While the FLiRT variants are likely to keep evolving after summer, entirely new subvariants cannot be ruled out. "An Omicron-like event” seems to have occurred every year in the fall since 2021, says Sato. 

Here's what you need to know about the new variants and the new vaccines.

What are FLiRT variants?

The "FLiRT" variant family includes the majority of currently circulating variants, identified with the letters KP, JN, and the variant LB.1.

The unofficial name "FLiRT" is an acronym for a set of mutations on the spike protein of SARS-CoV-2, the virus that causes COVID-19. The virus uses spike protein to bind with ACE2 receptors in our nose and lung cells to cause infection. 

All proteins are made up of amino acids that string together like beads. Mutations can change one amino acid to another, thereby altering the behavior of the protein and making the virus more or less infectious, or able to dodge immunity. 

The FLiRT subvariant family members are descended from the JN.1 variant that was dominant in the U.S. in early 2024. JN.1 itself was highly unusual because it acquired 41 mutations that differentiated it from Omicron XBB.1.5, which is the variant upon which the current bivalent COVID booster is based.

Should you get the new vaccines?

The two updated mRNA vaccines, manufactured by Pfizer-BioNTech and Moderna, target a FLiRT variant called KP.2. Anyone over the age of 12 can get the new shots, as long as they haven't received a booster in the last two months.

“Vaccination continues to be the cornerstone of COVID-19 prevention,” Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research said in a statement.

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Another vaccine targeting the variant JN.1 and manufactured by Novovax is also under review and could be approved soon.

Previous research also showed that older vaccines based on XBB.1.5, an earlier subvariant of Omicron, were still effective in preventing severe COVID-19. While this vaccine produces antibodies that still target the FLiRT variants, the efficiency is notably reduced. A recent infection from the JN.1 variant also seems to provide strong protection against all the FLiRT variants.  

That said, the CDC recommends that everyone six months and older get a COVID vaccine. Those at high risk for serious COVID-19 should get vaccinated with the most recent versions available. 

How alarming are FLiRT variants? 

Coronaviruses, such as SARS-CoV-2, frequently mutate to avoid recognition by antibodies. The two FLiRT mutations remove the sites on the virus where antibodies bind the SARS-CoV-2 virus.  

Additional mutations on the FLiRT variants can either help the virus bind more efficiently to ACE2 receptors making it more infectious, help it evade previous immunity, or both, says Adrian Esterman, an epidemiologist at the University of South Australia, Allied Health & Human Performance in Adelaide, Australia

Early studies show that all existing FLiRT subvariants are very good at dodging previous immunity acquired through multiple COVID vaccinations—including the most recent COVID bivalent booster—or a breakthrough infection from a previous strain of Omicron.

But the good news is that by escaping the antibodies, the FLiRT variants have also seem to lost some ability to infect their target because the virus needed the original antibody-binding sites to bind the ACE2 receptor and enter cells. 

"These variants are not yet particularly concerning, even with the new mutations that affect certain aspects of the virus's biology," says Shan-Lu Liu, a virologist at the Ohio State University. 

It is common for viruses to acquire mutations that help them dodge immunity, which can affect their ability to infect cells, says Liu. "The viruses can quickly evolve new mutations to restore their infectivity."   

But in the meantime, Sato thinks that waning immunity from previous vaccinations and infections, coupled with the FLiRT variant's ability to dodge remaining immunity, are probably the main reason for the recent surge in infections.   

Liu also agrees that the currently rising numbers of COVID infections are mostly due to low booster uptake and increased summer travel. 

Are COVID medicines still effective?

Emergency department visits, hospitalizations, and deaths have all spiked during this summer but are still much lower compared to earlier waves of the pandemic. 

There is no indication that these new FLiRT variants are more dangerous than other Omicron strains.

A study shows that Paxlovid is still effective against FLiRT variants. Other antiviral drugs such as molnupiravir and remdesivir are also expected to work since their mechanism of action is not affected by mutations in the spike protein.