04 COVID Link Gelles 508

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Centers for Disease Control and Prevention
National Center for Immunization and Respiratory Diseases
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Vaccine effectiveness of
updated (2023 -2024) COVID -19 vaccines
February 2024
Ruth Link- Gelles, PhD, MPH
CDR, US Public Health Service
Vaccine Effectiveness Program LeadCoronavirus and Other Respiratory Viruses Division
2VE refresher
Context for interpretation of VE
VE against:
–Symptomatic SARS -CoV -2, Increasing Community Access to Testing (ICATT) program
–COVID -19-associated emergency department/urgent care encounters, VISION Network
–COVID -19-associated hospitalizations , VISION and IVY NetworksAgenda: vaccine effectiveness (VE) of updated  2023 -24 
COVID -19 vaccines
33Test
negative 
design
Vaccine effectiveness = (1 – adjusted odds ratio)*100%
Odds of vaccination in cases
Odds of vaccination in controlswhere odds ratio = CaseControl
Slide adapted from Amadea Britton.Person with
COVID -19-like illness
SARS -CoV-2 test
COVID -19
vaccinationstatus
44•Benefits
•Reduces bias from health- care seeking behavior by including 
cases and controls who presented to care and received 
testing (usually at the same facility)
•Efficient use of an existing surveillance system
•Considerations
•Dependent on sensitivity and specificity of diagnostic testing 
•Controls + for another vaccine preventable disease can bias results. Sensitivity analyses dropping RSV+ and flu+ positive controls can be helpful.Test
negative 
design
Slide adapted from Amadea Britton.
5Efficacy and effectiveness are population level  estimates.
Adapted from: https://www.who.int/news -room/feature- stories/detail/vaccine -efficacy -effectiveness -and -protection
If a vaccine has an
effectiveness of 80 percent:
66Context for interpreting VE across age groups
* Internal CDC data. Data on persons aged ≥16 years is from a longitudinal, national cohort of >35,000 blood donors.High rates of SARS -CoV- 2 infection- induced immunity by July –August 2023.*
VE findings should be interpreted as the incremental benefit  provided by COVID- 19 vaccination in a 
population with a high prevalence of infection- induced immunity.89%
89%
84%
72%16-29 years
30-49 years
50-64 years
≥65 years
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent with infection- induced immunityPercent of persons with infection -induced immunity,
based on anti -nucleocapsid results from blood donors
7Previously for COVID- 19 VE :
–Absolute VE: comparing the frequency of health outcomes in vaccinated and unvaccinated 
people
•Example: comparing outcomes in people vaccinated with an updated  (2023 -24)  dose versus  no COVID -19 
vaccine received ever
–Relative VE : comparing the frequency of health outcomes in people who received one type of 
vaccine to people who received a different vaccine or by comparing people who received more 
vaccine doses to those who received fewer doses
•Example: comparing outcomes in people vaccinated with an updated  (2023 -24)  dose versus no updated (2023 -
24) dose
Analyses presented today:
–Vaccinated group: received updated (2023 -24) dose
–Comparison group: eligible for, but did not receive, an updated (2023 -24)  dose , regardless of past vaccination 
historyMeasuring updated (2023- 2024) COVID- 19 VE
8
Updates to vaccine effectiveness 
against symptomatic infection
Increasing Community Access to Testing (ICATT) program
Data updated from MMWR published February 1, 2024:
Link -Gelles R, Ciesla AA, Mak J, et al. Early Estimates of Updated 2023 –2024 (Monovalent XBB.1.5) COVID -19 Vaccine 
Effectiveness Against Symptomatic SARS -CoV -2 Infection Attributable to Co -Circulating Omicron Variants Among 
Immunocompetent Adults — Increasing Community Access to Testing Program, United States, September 2023 –January 
2024. MMWR Morb  Mortal Wkly  Rep 2024;73:77 –83. DOI: http://dx.doi.org/10.15585/mmwr.mm7304a2
9Nationwide community -based drive- through SARS- CoV-2 testing via pharmacies
Self-reported vaccine history at time of registration for SARS- CoV-2 testing*
Design : Test -negative analysis**
Population : Adults ≥18 years with ≥1 COVID -like symptom and nucleic acid amplification testing (NAAT)
Major exclusion criteria: Individuals with immunocompromising conditions, reported a positive SARS-
CoV-2 test in preceding 90 days***
Periods for analysis:
•Full analysis included tests from September 21, 2023 – February 18, 2024
•Sub- analysis using SGTF**** included tests from October 27, 2023 – February 15, 2024Increasing Community Access to Testing: VE from national pharmacy testing 
data
*At 5% of testing encounters, COVID -19 vaccination status is collected by clinician interview
**Odds ratios were calculated using multivariable logistic regression, adjusting for single year of age, gender, race/ethnici ty, SVI of the testing location (<0.5 versus ≥0.5), pharmacy contractor, underlying conditions (presence versus 
absence), U.S. Department of Health and Human Services region of testing location, and date of testing
***Additional exclusion criteria: 1) reported receiving Novavax as their most recent dose and reported receiving <2 total COV ID-19 vaccine doses; 2) reported receiving a Janssen (Johnson & Johnson) COVID -19 vaccine dose after May 
12, 2023; 3) received most recent dose <7 days prior to the date of testing or during September 1 -12, 2023; or 4) registered for  testing with a version of the questionnaire that only reported month and year of the most recent vaccine 
dose rather than calendar date.**** Results of spike gene (S -gene) amplification in real -time reverse transcription –polymerase chain reaction (RT -PCR) can be u sed to distinguish certain SARS -CoV-2 lineages over time (2). S -gene target presence (SGTP) was 
detected in most lineages that circulated in 2023, including XBB lineages, whereas S -gene target failure (SGTF) is detected in J N.1 and other BA.2.86 lineages
Link-Gelles, et al. MMWR 2024: http://dx.doi.org/10.15585/mmwr.mm7304a2
 (Results updated with additional month of data since publication.)
1010ICATT: VE of 2023 -2024 COVID -19 vaccine against symptomatic infection 
among adults aged ≥18 years, by age group and time since dose
September 2023 – February 2024
COVID- 19 dosage pattern/age groupTotal
testsSARS -CoV -2-
test -positive,
N (%)Median interval
since last dose among 
vaccinated among those 
vaccinated, days (IQR)Adjusted VE
(95% CI)
≥18 years
No updated (2023 -2024) monovalent dose (ref) 10,829 4,080 (38) 676 (427 to 859) Ref
Updated (2023- 2024) monovalent dose, ≥7 days 1,537 408 (27) 61 (33 to 86) 49 (42 –  55)
Updated (2023- 2024) monovalent dose, 7 -59 days earlier 735 170 (23) 32 (20 to 46) 55 (46 –  62)
Updated (2023- 2024) monovalent dose, 60- 119 days earlier 720 214 (30) 82 (71 to 95) 43 (33 –  52)
18-49 years
No updated (2023 -2024) monovalent dose (ref) 8,676 3,152 (36) 691 (439 to 877) Ref
Updated (2023- 2024) monovalent dose, ≥7 days 943 229 (24) 61 (34 to 85) 50 (41 –  58)
Updated (2023- 2024) monovalent dose, 7 -59 days earlier 452 87 (19) 32 (19 to 46) 61 (50 –  69)
Updated (2023- 2024) monovalent dose, 60- 119 days earlier 445 130 (29) 81 (70 to 94) 39 (24 –  51)
≥50 years
No updated (2023 -2024) monovalent dose (ref) 2,153 928 (43) 593 (400 to 800) Ref
Updated (2023- 2024) monovalent dose, ≥7 days 594 179 (30) 62 (32 to 89) 45 (32 –  55)
Updated (2023- 2024) monovalent dose, 7 -59 days earlier 283 83 (29) 32 (21 to 44) 43 (24 –  57)
Updated (2023- 2024) monovalent dose, 60- 119 days earlier 275 84 (31) 84 (72 to 98) 47 (29 –  60)
0 20 40 60 80 100
Vaccine  Effectiveness (%)Link-Gelles, et al. MMWR 2024: http://dx.doi.org/10.15585/mmwr.mm7304a2  (Results updated with additional month of data since publication.)
  
11Trends in estimated proportions of SARS -CoV -2 S-gene target presence 
and variant proportions and Nowcast projections from genomic 
surveillance
S-gene = spike gene; SGTF = S -gene target failure; SGTP = S -gene target presence Specimen collection date (2 -week period ending)

1212ICATT: VE of 2023 -2024 COVID -19 vaccine against symptomatic infection among 
adults aged ≥18 years, by S- gene target (SGT) result and time since dose
October 2023 –  February  2024
COVID- 19 dosage pattern/age groupTotal
testsSARS -CoV -2 negative SARS -CoV -2 positive
Adjusted VE
(95% CI)No.
(row %)Median interval 
since last dose 
among vaccinated, 
days (IQR) N (row %)Median interval
since last dose 
among vaccinated, 
days (IQR)
SGT presence (likely non- JN.1)
No updated (2023 -2024) monovalent dose (ref) 2,497 1,705 (68) 659 (403 to 820) 422 (17) 671 (405 to 801) Ref
Updated (2023- 2024) monovalent dose, 60- 119 days earlier 329 252 (77) 84 (72 to 98) 25 (8) 73 (69 to 83) 60 (36 to 74)
SGT failure (likely JN.1)
No updated (2023 -2024) monovalent dose (ref) 2,497 1,705 (68) 659 (403 to 820) 370 (15) 682 (426 to 822) Ref
Updated (2023- 2024) monovalent dose, 60- 119 days earlier 329 252 (77) 84 (72 to 98) 52 (16) 86 (72 to 95) 45 (22 to 62)
0 20 40 60 80 100
Vaccine  Effectiveness (%)
Link-Gelles, et al. MMWR 2024: http://dx.doi.org/10.15585/mmwr.mm7304a2  (Results updated with additional month of data since publication.)
  
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VISION ED/UC
Joint VISION/IVY MMWR to be published February 29, 2024
1414VISION Multi -Site Network of Electronic Health Records
369 emergency rooms and urgent cares/229 hospitals
Design: Test-negative analysis
Population: Adults visiting a participating 
emergency department or urgent care 
(ED/UC) or hospitalized with COVID -19-like 
illness (CLI) with a SARS- CoV -2 NAAT test 
result within 10 days before or 72 hours after encounter
−Cases : CLI with positive  NAAT for SARS -CoV -2 and 
no positive NAAT for RSV or influenza
–Controls : CLI with negative  NAAT for SARS -CoV-2 
and no positive NAAT for influenza
Vaccination data: Documented by electronic health records and state 
and city registries
1515VISION: VE of 2023 -2024 vaccine against ED/UC encounters among 
immunocompetent adults aged ≥18 years, by age group
September 2023 – January 2024
VE estimates adjusted for age, sex, race and ethnicity, geographic region, and calendar time. MMWR to be published February 2 9, 2024COVID- 19 dosage pattern/age groupCOVID- 19 
case -
patients
N (Col %)COVID- 19 
control -
patients
N (Col %)Median interval
since last dose among 
vaccinated among those 
vaccinated, days (IQR)Adjusted VE
(95% CI)
≥18 years
No updated (2023 -2024) monovalent dose (ref) 15,932 (92) 98,218 (88) 669 (403- 792) Ref
Updated (2023- 2024) monovalent dose, ≥7 days 1,297 (8) 13,378 (12) 44 (26- 64) 47 (44- 50)
Updated (2023- 2024) monovalent dose, 7 -59 days earlier 825 (5) 9,372 (8) 33 (20- 46) 51 (47- 54)
Updated (2023- 2024) monovalent dose, 60- 119 days earlier 472 (3) 4,006 (4) 74 (66- 83) 39 (33- 45)
18-64 years
No updated (2023 -2024) monovalent dose (ref) 10,582 (97) 69,423 (94) 697 (480- 832) Ref 
Updated (2023- 2024) monovalent dose, ≥7 days 377 (3) 4,739 (6) 42 (24- 62) 50 (44- 55)
Updated (2023- 2024) monovalent dose, 7 -59 days earlier 259 (2) 3,457 (5) 31 (19- 45) 52 (45- 58)
Updated (2023- 2024) monovalent dose, 60- 119 days earlier 118 (1) 1,282 (2) 73 (66- 83) 45 (34- 55)
≥65 years
No updated (2023 -2024) monovalent dose (ref) 5,350 (85) 28,795 (77) 509 (362- 733) Ref 
Updated (2023- 2024) monovalent dose, ≥7 days 920 (15) 8,639 (23) 46 (27- 66) 45 (41- 49)
Updated (2023- 2024) monovalent dose, 7 -59 days earlier 566 (9) 5,915 (16) 33 (21- 46) 49 (44- 54)
Updated (2023- 2024) monovalent dose, 60- 119 days earlier 354 (6) 2,724 (7) 74 (66- 83) 37 (29- 44)
0 20 40 60 80 100
Vaccine  Effectiveness (%)
16
VISION/IVY Hospitalization
Joint VISION/IVY MMWR to be published February 29
1717VISION: VE of 2023 -2024 vaccine against hospitalization among 
immunocompetent adults aged ≥18 years, by age group
September 2023 – January 2024
VE estimates adjusted for age, sex, race and ethnicity, geographic region, and calendar time. MMWR to be published February 2 9, 2024
*Some estimates are imprecise, which might be due to a relatively small number of persons in each level of vaccination or case  status. This imprecision indicates that the actual 
VE could be substantially different from the point estimate shown, and estimates should therefore be interpreted with caution. A dditional data accrual could increase precision 
and allow more precise interpretation.COVID- 19 dosage pattern/age groupCOVID- 19 
case -
patients
N (Col %)COVID- 19 
control -
patients
N (Col %)Median interval
since last dose among 
vaccinated among those 
vaccinated, days (IQR)Adjusted VE
(95% CI)
≥18 years
No updated (2023 -2024) monovalent dose (ref) 4,194 (91) 28,715 (87) 627 (383- 765) Ref
Updated (2023- 2024) monovalent dose, ≥7 days 395 (9) 4,199 (13) 42 (24- 62) 52 (47- 57)
Updated (2023- 2024) monovalent dose, 7 -59 days earlier 270 (6) 3,056 (9) 32 (19- 45) 53 (46- 59)
Updated (2023- 2024) monovalent dose, 60- 119 days earlier 125 (3) 1,143 (3) 73 (66- 81) 50 (40- 59)
18-64 years
No updated (2023 -2024) monovalent dose (ref) 938 (96) 11,342 (95) 685 (447- 829) Ref
Updated (2023- 2024) monovalent dose, ≥7 days 38 (4) 657 (5) 38 (22- 58) 43 (20- 59)
Updated (2023- 2024) monovalent dose, 7 -59 days earlier 28 (3) 503 (4) 30 (19- 44) 42 (14- 61)
Updated (2023- 2024) monovalent dose, 60- 119 days earlier 10 (1) 154 (1) 74 (67- 81) 45 (-6-71)*
≥65 years
No updated (2023 -2024) monovalent dose (ref) 3,256 (90) 17,373 (83) 549 (370- 745) Ref
Updated (2023- 2024) monovalent dose, ≥7 days 357 (10) 3,542 (17) 43 (25- 62) 53 (47- 58)
Updated (2023- 2024) monovalent dose, 7 -59 days earlier 242 (7) 2,553 (12) 32 (19- 46) 54 (47- 60)
Updated (2023- 2024) monovalent dose, 60- 119 days earlier 115 (3) 989 (5) 73 (66- 81) 50 (39- 59)
0 20 40 60 80 100
Vaccine  Effectiveness (%)
1818IVY Network —  26 hospitals, 20 U.S. States
Design : Case -control, prospective enrollment
Population: Adults  aged  ≥18 years  hospitalized with 
Acute respiratory illness (ARI)*
–Cases: ARI and test  positive  for SARS -CoV-2 by NAAT or 
antigen test within 10 days of illness and not positive for 
influenza or RSV
–Controls : ARI and test negative  for SARS -CoV-2 and influenza 
by NAAT within 10 days of illness
Vaccination data: Electronic medical records (EMR), 
state and city registries, and self -report
Specimens: Upper respiratory specimens obtained 
for central RT -qPCR testing and sequencing
*ARI is defined as presence of any one of the following: fever, cough, shortness of breath, chest imaging consistent with pne umo nia, hypoxemia
1919IVY: VE of 2023 -2024 vaccine against hospitalization among 
immunocompetent adults aged ≥18 years, by age group
September 2023 – January 2024
September 2023 – January 2024
VE estimates adjusted for age, sex, race and ethnicity, geographic region, and calendar time. MMWR to be published February 2 9, 2024COVID- 19 dosage pattern/age groupCOVID- 19 
case -
patients
N (Col %)COVID- 19 
control -
patients
N (Col %)Median interval
since last dose among 
vaccinated among those 
vaccinated, days (IQR)Adjusted VE
(95% CI)
≥18 years
No updated (2023 -2024) monovalent dose (ref) 1100 (92) 2570 (88) 645 (387- 781) Ref
Updated (2023- 2024) monovalent dose, ≥7 days 94 (8) 353 (12) 47 (25- 71) 43 (27 to 56)
≥65 years
No updated (2023 -2024) monovalent dose (ref) 747 (91) 1284 (84) 573 (375- 752) Ref
Updated (2023- 2024) monovalent dose, ≥7 days 76 (9) 245 (16) 48 (26- 72) 48 (31 to 61)
0 20 40 60 80 100
Vaccine  Effectiveness (%)
20Updated (2023 -2024) COVID -19 vaccination provided increased protection against 
symptomatic SARS- CoV -2 infection and COVID -19-associated ED/UC visits and 
hospitalizations compared to no updated vaccine dose.
Receipt of updated (2023- 2024) COVID -19 vaccine provides protection against JN.1 
and other circulating variants
These are relatively early estimates from all 3 VE studies with no substantial waning; 
however, waning is expected,  and CDC will continue monitoring VEConclusions
21CDC COVID -19 Vaccine Effectiveness 
and Policy Team
Amadea Britton
Allison Ciesla
Monica Godfrey
Eric Griggs
Katherine Fleming-Dutra
Dani Moulia
Morgan Najdowski
Erica OkwuaziAnd others, including:
Sarah Ball
Jennifer DeCuir
Monica Dickerson
Margaret Dunne
Shikha Garg
Jefferson Jones
Anastasia Lambrou
Patrick Mitchell
Clint Paden
Palak Patel
And many more!!!Acknowledgements
Caitlin Ray
Sarah Reese
Elizabeth Rowley
Philip Shirk
Benjamin Silk
Zach Smith
Diya Surie
Mark Tenforde
Zack Weber
VISION and IVY site investigatorsJosephine Mak
Amanda Payne
Lauren Roper
Ami Shah
Megan Wallace
Ryan Wiegand