Latest COVID-19 vaccines reduce hospitalization risk by around half
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Key takeaways:
- The 2023-24 formula COVID-19 and influenza vaccines are about 50% effective at preventing severe disease.
- The pace and frequency of new COVID-19 variants underscores the need for monitoring of vaccine effectiveness.
The latest COVID-19 vaccines reduce the risk for hospitalization or visits to an ED or urgent care by around 50%, according to interim data published in MMWR.
This season’s influenza vaccines were similarly protective against hospitalization among children and adults, early estimates published in MMWR showed.
The updated, monovalent COVID-19 vaccines recommended by the CDC in September target omicron XBB subvariants of SARS-CoV-2.
“Although studies have found that updated COVID-19 vaccines elicit broadly cross-protective neutralizing antibodies, including against XBB lineages and JN.1” — currently the predominant omicron lineage — “the pace and frequency with which new SARS-CoV-2 lineages have displaced predecessors underscores the need for ongoing monitoring of COVID-19 vaccine effectiveness (VE) and for periodic COVID-19 antigen updates,” Jennifer DeCuir, MD, PhD, from the CDC’s Coronavirus and Other Respiratory Diseases Division, and colleagues wrote in MMWR.
DeCuir and colleagues analyzed data on 128,825 people who had a medical encounter (ME) or were hospitalized for COVID-19 at one of 369 EDs and 229 hospitals in eight states in the Methods for Virtual SARS-CoV-2, Influenza and Other Respiratory Viruses Network (VISION). Of these, 17,229 received a positive test for SARS-CoV-2 and 111,569 received a negative test.
Among VISION MEs and hospitalizations, 8% of people with a positive SARS-CoV-2 test had received an updated COVID-19 vaccine and 12% of people with a negative SARS-CoV-2 test had received the updated vaccine.
Overall, VE against COVID-19-associated ME or hospitalization was 51% (95% CI = 47%-54%) in the first 7 to 59 days after receiving an updated vaccine dose and 39% (95% CI = 33%-45%) in the 60 to 119 days after an updated vaccine dose.
Another study published in MMWR showed that the 2023-2024 influenza vaccines have VEs that are relatively similar to previous vaccines.
“These interim estimates indicate that receipt of a 2023-2024 influenza vaccination reduced the risk for medically attended influenza-associated outpatient visits and hospitalization among children and adolescents and among adults, including those older than age 65 years, consistent with results from previous years,” Aaron M. Frutos, PhD, from the CDC’s Influenza Division, and colleagues wrote.
Frutos and colleagues analyzed data from four CDC-affiliated VE networks of health care facilities in 22 states on people who received outpatient medical care or were hospitalized for acute respiratory illness (ARI). It was the first time that interim influenza VE data were available at the same time for both adults and children from four different vaccine effectiveness networks.
They estimated that interim VE against any influenza-associated ARI among adults ranged from 33% to 49% in outpatient settings and 41% to 44% against influenza-associated hospitalization. Among children, interim VE against influenza was 59% to 61% in outpatient settings and 52% to 61% against influenza-associated hospitalization.
A second study of 2023-2024 influenza vaccine effectiveness by Sophie Zhu, PhD, an investigator in the CDC’s Epidemic Intelligence Service, and colleagues found similar VE rates based on nearly 680,000 people in California who had an influenza test between Oct. 1, 2023, and Jan. 31, 2024.
Zhu and colleagues found that 28% of people who received an influenza test had received an influenza vaccine, including 18% of people who tested positive and 29% of people who tested negative.
Overall, they found that adjusted VE was 45% against receiving a positive influenza test, with VE highest among people aged younger than 18 years at 56%, and that it declined among older age groups — 48% among adults aged 18 to 49 years, 36% among people aged 50 to 64 years and 30% among people aged older than 65 years.
References:
- DeCuir J, et al. MMWR Morb Mortal Wkly Rep. 2024;doi:10.15585/mmwr.mm7308a5.
- Frutos AM, et al. MMWR Morb Mortal Wkly Rep. 2024;doi:10.15585/mmwr.mm7308a3.
- Zhu S, et al. MMWR Morb Mortal Wkly Rep. 2024;doi:10.15585/mmwr.mm7308a4.
- CDC. COVID data tracker: Variant proportions. https://covid.cdc.gov/covid-data-tracker/#variant-proportions. Updated March 1, 2024. Accessed March 1, 2024.
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