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The recently updated COVID vaccines showed protection against serious virus-related outcomes in immunocompetent adults, data from the CDC's IVY and VISION networks showed.

From September 2023 to January 2024, vaccine effectiveness (VE) against COVID-related emergency department or urgent care encounters landed at 47% (95% CI 44-50), while protection against hospitalizations associated with the coronavirus ranged from 43% (95% CI 27-56) to 52% (95% CI 47-57), reported Jennifer DeCuir, MD, PhD, of CDC's National Center for Immunization and Respiratory Diseases, and colleagues.

"The comparison group included both unvaccinated persons and persons who had received original monovalent or bivalent doses only," the researchers wrote in the . "Thus, these results support current CDC recommendations for updated COVID-19 vaccination, including among persons who have previously received original monovalent or bivalent COVID-19 vaccines and those who have never been vaccinated, irrespective of previous infection history."

In September 2023, the FDA authorized and CDC's Advisory Committee on Immunization Practices recommended the 2023-2024 COVID-19 vaccines for adults and kids ages 6 months and older. The updated shots were designed to target the XBB.1.5 Omicron subvariant based on recommendations from FDA staff and outside advisors.

But uptake of the vaccines has been low: the CDC's latest estimates show that just 22% of U.S. adults have received the latest vaccines, including 42% of adults 65 and over.

The current study included data from 369 emergency departments and urgent care clinics and 229 hospitals across eight states in (Virtual SARS-CoV-2, Influenza, and Other respiratory viruses Network), along with 26 hospitals in 20 states in the (Investigating Respiratory Viruses in the Acutely Ill) network.

The analysis on emergency department and urgent care visits included 128,825 adults (median age 52 years, 61% female, 64% white) who visited facilities within VISION for COVID-like illness, including 17,229 case patients (those who received a positive SARS-CoV-2 test) and 111,596 controls (those who received a negative SARS-CoV-2 test). Overall, 8% of the case patients and 12% of controls had received the 2023-2024 COVID vaccine dose.

Across all adults, VE against emergency department and urgent care visits was slightly higher for individuals who had received the vaccine 7-59 days earlier compared with those who received the vaccine 60-119 days earlier (51% vs 39%, respectively). Protection was higher for adults ages 18-64 than for adults ages 65 years and up (50% vs 45%).

The analysis on COVID-related hospitalization included 37,503 hospitalizations (median age 71 years, 54% female, 71% white) from the VISION network (including 4,589 case patients) and 4,117 hospitalizations (median age 68 years, 52% female, 57% white) from the IVY network (including 1,194 case patients).

In the VISION subset, 9% of the case patients and 13% of the controls had received the 2023-2024 vaccine. VE against COVID-related hospitalization was slightly higher in the first 7-59 days after vaccination compared with the 60-119 days after vaccination (53% vs 50%). Interestingly, VE was higher among patients ages 65 and older compared with adults under 65 years (53% vs 43%).

In the IVY subset, 8% of the case patients and 12% of the controls had received the updated vaccine. Here, VE against COVID-related hospitalization was again higher among those ages 65 and older (48% vs 43%). Estimates based on time since vaccination were not available.

"Despite different populations, methods, and outcomes, estimates of the effectiveness of updated COVID-19 vaccines were aligned across the VISION and IVY analyses," the researchers wrote. "VE estimates were also similar to those recently published from another CDC VE platform, which measured VE against symptomatic SARS-CoV-2 infection, and to a , which measured VE against hospitalization among patients aged ≥65 years."

Whole genome sequencing data on 952 specimens from IVY showed that 16% had XBB.1.5-like spike proteins, 58% had EG.5-like spike proteins, 20% had HK.3-like spike proteins, and 6% had JN.1-like spike proteins, a descendent of BA.2.86 with more than 30 substitutions in the spike protein compared with XBB.1.5, "some of which might be associated with immune escape," noted DeCuir and colleagues. By early January, JN.1 accounted for nearly two-thirds of circulating lineages in the U.S.

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