Data Support Protective Effects of Omicron COVID Vaccine

Use of the 2024-2025 COVID-19 vaccine that targets the Omicron strain was associated with significantly fewer emergency department and urgent care visits compared to no vaccination, especially in older adults, based on new data published by the Centers for Disease Control and Prevention (CDC).

In July 2024, the CDC’s Advisory Committee on Immunization Practices recommended a COVID-19 vaccine for 2024-2025 for all individuals aged 6 months and older. The approved vaccine for 2024-2025 targeted the Omicron JN.1 and JN.1-derived lineages, wrote Ruth Link-Gelles, PhD, of the CDC’s National Center for Immunization and Respiratory Diseases, and colleagues. 

The researchers reviewed data from the Virtual SARS-CoV-2, Influenza, and Other respiratory viruses Network and Investigating Respiratory Viruses in the Acutely Ill networks on adults aged 18 years and older with COVID-19-like illness. They estimated vaccine effectiveness (VE) for individuals aged 18 years and older, 18-64 years, and 65 years and older, and compared VE in adults with and without immunocompromising conditions.

Overall, VE was 33% against emergency department/urgent care visits in the first 7-119 days after vaccination, 36% during the first 7-59 days after vaccination, and 30% during 60-119 days after vaccination. 

Among adults aged 65 years and older, VE was 40% and 46% in those with and without immunocompromising conditions, respectively.

“Because of both lower hospitalization rates and lower vaccination rates, VE could not be estimated for children and adolescents aged 5-17 years for either outcome or for adults aged 18-64 years against hospitalization,” the researchers wrote. 

The analyses did not account for previous COVID-19 infection or vaccination (including the original monovalent, bivalent, or 2023-2024 vaccines), the researchers noted.

“VE should therefore be interpreted as the added benefit of 2024-2025 COVID-19 vaccination in a population with high levels of infection-induced immunity, vaccine-induced immunity, or both,” they wrote in their discussion. 

The findings were limited by other factors including the potential that patients’ ED/UC visits were for illnesses other than COVID-19, which might have impacted estimates of VE, the researchers wrote. Other potential limitations include misclassification of vaccine status, inadequate data on younger age groups, and confounding factors such as behavior modifications and outpatient antiviral treatments, they said. 

However, the results support the value of a 2024-2025 COVID-19 vaccine in protecting against disease-related emergency department/urgent care visits and hospitalizations, especially in vulnerable groups, they concluded.

Even an Uneven Match Is Worthwhile

“The effectiveness of the COVID vaccines can vary depending on which variants are targeted in the vaccine, which variants are circulating, and host factors,” said Shirin A. Mazumder, MD, and infectious diseases specialist in Memphis, Tenn., in an interview.

Although the strains in the vaccine and those currently circulating are not a perfect match, the latest COVID vaccine remains an important tool in COVID risk reduction, and the results of the current effectiveness review were not surprising, said Mazumder. 

“There is a demonstrated decrease in urgent care and emergency room visits associated with COVID vaccination compared to those who did not get vaccinated,” she emphasized. Vaccination also was associated with a significant reduction in cases of severe infection requiring hospitalization among high-risk groups, such as those older than 65 years, and older adults with immunocompromising conditions, she said. 

Barriers and Next Steps

Low vaccine uptake remains a challenge in preventing COVID infections, Mazumder told Medscape Medical News. “According to CDC data, as of February 15, 2025, only 12.1% of children, 13.8% of pregnant women and 23% of adults reported receiving the 2024-2025 COVID vaccine,” she said. “Ongoing education of the public on the importance of vaccines is critical for public health in this country,” she added. 

“Vaccine fatigue,” is another reported concern among individuals who tend to avoid vaccinations, especially during the respiratory virus season when multiple vaccines are recommended, but a combination flu and COVID vaccine that is currently under evaluation may help alleviate the burden of multiple shots, said Mazumder. 

“The pace at which the variants change rendering previous versions of the COVID vaccine less effective and the waning levels of vaccine protection over time are also existing barriers to vaccination,” she said. 

Additional limitations to the current report include a lack of data on VE in the pediatric population, or the effectiveness of the COVID vaccine in preventing long COVID rates and COVID related deaths, Mazumder noted. “In addition, the report did not evaluate the effectiveness of the individual COVID vaccines currently available by different manufacturers, and these are some areas where additional evaluation may be helpful,” she said.

Mazumder had no financial conflicts to disclose.