How much extra protection did the 2024–2025 COVID-19 vaccine give adults in its first months? CDC's interim estimates, from September 2024 to January 2025, compare adults who got a 2024–2025 dose with those who didn't — whatever their earlier vaccines or infections.
Headline results
Protection during the first 7–119 days after vaccination:
| Outcome | Who | Vaccine effectiveness |
|---|---|---|
| Emergency department (ED) or urgent care (UC) visit | adults 18 and older | 33% |
| … | adults 18–64 | 30% |
| … | adults 65 and older | 35% |
| Hospitalization | adults 65+ without immune problems — VISION network | 45% |
| … | the same group — IVY network | 46% |
| … | adults 65+ with immunocompromising conditions (VISION) | 40% |
Against ED/UC visits for all adults, effectiveness was 36% in the first 7–59 days and 30% at 60–119 days. For hospitalization among older adults, protection held up: VISION measured 42% and then 48%, and IVY 42% and then 47%, over the same two windows.
Why a new vaccine
- From September 24, 2023 to August 11, 2024, about 800,000 COVID-19 hospitalizations occurred in the United States; adults 65 and older accounted for 70%. Vaccination averted about 68,000 hospitalizations in the 2023–24 season.
- In 2024, Omicron JN.1 and its descendants took over — genetically distant from the XBB strains the 2023–2024 vaccines were built on.
- On June 27, 2024, CDC's Advisory Committee on Immunization Practices (ACIP) recommended a 2024–2025 vaccine for everyone 6 months and older.
| 2024–2025 vaccine (for ages 12+) | Based on | FDA action, August 2024 |
|---|---|---|
| Moderna | Omicron KP.2 | approved |
| Pfizer-BioNTech | Omicron KP.2 | approved |
| Novavax | Omicron JN.1 | authorized |
Most adults need one dose; people with moderate or severe immunocompromise and adults 65 and older are recommended additional doses, depending on their history and time since their last dose.
How it was measured
Both networks used a test-negative design: among adults with COVID-19–like illness who were tested, they compared vaccination between those who tested positive (case-patients) and those who tested negative (controls). Estimates were adjusted for age, sex, race and ethnicity, calendar time and region.
| Network | What it covers | Included |
|---|---|---|
| VISION | electronic health records from 373 ED/UCs and 241 hospitals in eight states | 137,543 ED/UC visits; 26,219 hospitalizations of adults 65+ without immune problems; 8,192 of adults 65+ with them |
| IVY | 26 hospitals in 20 states, enrolling patients prospectively, with central testing at Vanderbilt University Medical Center and sequencing at the University of Michigan | 1,929 hospitalized adults 65+ without immune problems |
People counted as vaccinated if their 2024–2025 dose came at least 7 days before the visit or illness. Case-patients also infected with flu or RSV were left out, as were controls who tested positive for flu (or, for those 60+, RSV).
Which variants were circulating
IVY sequenced 653 positive specimens from September 1 to December 31, 2024; CDC's national genomic surveillance sequenced 6,491. Both showed the same mix:
| Spike protein | IVY | National |
|---|---|---|
| KP.3-like | 52.1% | 52.8% |
| XEC-like | 19.3% | 13.8% |
| KP.2-like | 14.1% | 15.1% |
| JN.1-like | 8.4% | 14.3% |
| Other | 6.1% | 4.0% |
All were descendants of JN.1. XEC is closely related to the KP.2 and JN.1 strains in the vaccines, which may explain why protection held as XEC spread. From January 2025, a newer descendant, LP.8.1, began rising — 31% of national sequences by February 15, 2025 — so CDC stresses continued tracking of both effectiveness and variants.
Reading the numbers
- These figures are the added benefit of a 2024–2025 dose in a population that already had high immunity from earlier infections, vaccines or both. A late-summer 2024 surge, just before the new vaccines arrived, may have raised immunity to JN.1-type strains and lowered the measured effectiveness.
- Hospitalization rates were relatively low, so there were too few cases to estimate protection against critical illness — ICU admission, mechanical ventilation or death — which has historically been higher and longer-lasting. For the same reason, there are no estimates for children and teens (5–17) or for hospitalization in adults 18–64.
- Past seasons suggest similar protection across ages. Against ED/UC visits 60–179 days after a 2023–2024 dose, effectiveness was 50% for ages 5–17, 24% for adults 18–64 and 25% for adults 65+.
Limits
- Some case-patients may have come in for reasons other than COVID-19, which could lower the estimates.
- Vaccination status may sometimes have been recorded wrongly, likely making effectiveness look lower.
- Small numbers ruled out estimates for some groups, including younger ages.
- Other factors — such as people's own precautions or outpatient antiviral treatment — may still skew the results.
The authors conclude that a 2024–2025 dose added protection against ED/UC visits and hospitalization, for adults with and without immunocompromise, and that the findings support CDC and ACIP's recommendation that everyone 6 months and older get one. CDC continues to monitor the vaccines' effectiveness.
Sources
Based on Ruth Link-Gelles and colleagues (CDC COVID-19 Vaccine Effectiveness Collaborators), "Interim Estimates of 2024–2025 COVID-19 Vaccine Effectiveness Among Adults Aged ≥18 Years — VISION and IVY Networks, September 2024–January 2025," MMWR, volume 74, Centers for Disease Control and Prevention; a work of the United States government in the public domain.
许可协议： CC0 1.0（公有领域） · 改编自 www.cdc.gov
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