The COVID-19 virus continues to evolve, with new mutations arising that contribute to ongoing infections and reinfections globally. Recent surveillance from the Centers for Disease Control and Prevention (CDC) indicates that the latest strains of SARS-CoV-2, specifically KP.1, KP.2, and KP.3 and their sublineages, were responsible for the majority of infections in the United States as of early August. David Montefiori, a virology expert at Duke University, notes that these mutations bring a combination of slightly heightened transmissibility and partial immunity evasion, alongside reduced immunity from prior vaccinations and infections, setting up a potential summer surge in COVID-19 cases.
As of August 3, positive test rates had hit their highest levels since January 2022, with emergency room visits and hospitalizations on the rise, although deaths remained significantly lower compared to past surges, with only 340 reported in the week ending August 3, versus thousands during previous peaks.
In June, an FDA advisory committee unanimously suggested that vaccine manufacturers prepare updated versions of COVID-19 vaccines for the upcoming fall season, although no specific formulations have yet received approval.
Experts in infectious diseases have highlighted several key points about these new variants and the corresponding vaccines. Mutations in SARS-CoV-2 are frequent, but many are inconsequential. The currently dominant KP.2 and KP.3 variants, part of the FLiRT family, are considered subvariants of JN.1, which itself is a subvariant of omicron. While there are only minor differences among recent variants, all have demonstrated some ability to evade immunity, necessitating updated vaccines to match circulating strains.
The protection offered by COVID-19 vaccines or previous infections typically diminishes after three to four months. This summer’s surge in cases is likely due to many individuals not having recent vaccinations or infections, resulting in lower immunity levels. Studies have shown that vaccines targeting current strains become less effective over time, reinforcing the need to adjust vaccines to match prevailing variants.
The FDA faces a dilemma regarding the development of new vaccines, as they must choose whether to target the current dominant strain or adapt to variants expected to rise in prevalence later this year. While Novavax has developed a vaccine targeting the JN.1 strain, it also allows for the development of vaccines targeting the KP.2 variant. However, Moderna has already produced versions of their vaccine that can neutralize both the JN.1 and the FLiRT variants, promising availability soon.
Given the ongoing rise in COVID-19 cases, some experts advocate for mask-wearing in crowded or indoor settings, particularly for those at high risk. The CDC recommends isolation for anyone displaying COVID-19 symptoms and suggests high-risk individuals seek antiviral treatments like Paxlovid, which has shown effectiveness in reducing the risk of hospitalization and death.
Looking ahead, experts like Montefiori suggest that annual COVID-19 vaccinations may become a standard practice alongside seasonal flu shots, with new vaccine options, including combination shots that target both COVID-19 and influenza, being tested. The ongoing challenge remains ensuring widespread vaccination participation to protect vulnerable populations against severe illness and the potential risk of long COVID.