Centers for Disease Control and Prevention

National Center for Immunization and Respiratory DiseasesPhotographs and images included in this presentation are licensed solely for CDC/NCIRD online and presentation use. No rights are implied or extended for use in printing or any use by othe

COVID-19 vaccine effectiveness updates

19 April 2023Ruth Link-Gelles, PhD, MPHLCDR, US Public Health ServiceCOVID-19 Vaccine Effectiveness Program LeadCenters for Disease Control and Prevention
 Updates on vaccine effectiveness (VE) of monovalent vaccines 

symptomatic infection in children aged 6 months–4 years (Pfiz

and 6 months–5 years (Moderna)

 Update on VE of monovalent and bivalent vaccines against sev

adults with and without immunocompromising conditions

Organization of presentation
Estimates of Effectiveness of Monovalent mRNA Vaccines in Pr

Symptomatic SARS-CoV-2 Infection Among Children Aged 3–5 Increasing Community Access to Testing ProgramUpdated analyses based on: Fleming-Dutra KE, Ciesla AA, Roper, LE et al. Preliminary Estimates of Effectiveness of Monovalent mRNA VaccinSymptomatic SARS-CoV-2 Infection Among Children Aged 3–5 Years — Increasing Community Access to Testing Program, United States, July MMWR Morb Mortal Wkly Rep 2023;72:177–182. DOI: http://dx.doi.org/10.15585/mmwr.mm7207a3
Percent of people receiving COVID-19 vaccine by age and date 

– United States, December 14, 2020 – April 12, 2023https://covid.cdc.gov/covid-data-tracker/#vaccination-demographics-trends
 Nationwide community-based drive-through SARS-CoV-2 testing via p

 Self-reported vaccine history at time of registration for SARS-CoV-2 te Design: Test-negative, case-control analysis* Population: Immunocompetent children aged 3 – 4/5** years with ≥

symptom and nucleic acid amplification testing (NAAT)

 Period for analysis:

• Tested: July 4, 2022*** – April 8, 2023, BA.4/BA.5 and XBB predo

Increasing Community Access to Testing (ICATT) Program: VE oCOVID-19 vaccines against symptomatic infection in children ag

*Models adjusted for: age, gender, race, ethnicity, social vulnerability index and HHS region of the testing location, underlying conditions (presechain conducting the test, local incidence (cases per 100,000 by individual county and state in the 7 days before test date), and date of testing.** ICATT testing is generally limited to children ages 3 and up.***Analysis start date depended on vaccine/dose number being analyzed: Pfizer and Moderna 1st doses started 7/4/2022; Pfizer 2nd dose started 

started 8/1/2022; Pfizer 3rd dose started 9/19/2022. 
ICATT: Estimates of VE for primary series monovalent Moderna vaccine 

3–5 years) against symptomatic infection, July 4, 2022 – April 8, 2023

Updated from: Fleming-Dutra, Ciesla, Roper, et al. MMWR February 16, 2023.*Test registrants who report receiving COVID-19 vaccines are asked to report the total number of doses and manufacturer(s) of vaccines received 

and for the most recent dose, month and year of receipt; therefore, the number of months between a vaccine dose and testing is a whole number calculated as the difference between the month and year of testing and the month and year of the vaccine dose. For doses received in the same 

month or the month before SARS-CoV-2 testing, an additional question was asked to specify whether the dose was received ≥2 weeks before testing, and only doses received ≥2 weeks before testing were included. 17% and 21% of children who received 1 and 2 doses of Moderna, respectively, reported a prior infection >90 days before the current test.

Vaccination status (months since last dose) Total tests SARS-CoV-2 positive, N (%) Adjusted VE (95% CI)Moderna, 1 dose (partial series; ages 3-5 years)

July 4, 2022 – April 8, 2023

Unvaccinated 36,779 9,801 (27) Ref

1 monovalent dose (2 weeks–1 month)* 515 107 (21) 40 (25 to 52)

Moderna, 2 doses (complete series; ages 3-5 years)

August 1, 2022 – April 8, 2023

Unvaccinated 26,856 5,972 (22) Ref2 monovalent doses (2 weeks–6 months)* 1,613 183 (11) 47 (37 to 54)

2 monovalent doses (2 weeks–1 month)* 461 48 (10) 61 (47 to 71)2 monovalent doses (2–3 months)* 647 63 (10) 54 (41 to 65)2 monovalent doses (4–6 months)* 505 72 (14) 18 (-6 to 37)

-20 0 20 4

Vaccine Ef
ICATT: Estimates of VE for primary series monovalent Pfizer-BioNTech v

aged 3–4 years) against symptomatic infection, July 4, 2022 – April 8, 20

Updated from: Fleming-Dutra, Ciesla, Roper, et al. MMWR February 16, 2023.*Test registrants who report receiving COVID-19 vaccines are asked to report the total number of doses and manufacturer(s) of vaccines received 

and for the most recent dose, month and year of receipt; therefore, the number of months between a vaccine dose and testing is a whole number calculated as the difference between the month and year of testing and the month and year of the vaccine dose. For doses received in the same 

month or the month before SARS-CoV-2 testing, an additional question was asked to specify whether the dose was received ≥2 weeks before testing, and only doses received ≥2 weeks before testing were included. 18%, 19% and 21% of children who received 1, 2, and 3 doses of Pfizer, respectively, reported a prior infection >90 days before the current test.**There was insufficient power to stratify Pfizer-BioNTech 3-dose VE estimates by time since vaccination.

Vaccination status (months since last dose) Total tests SARS-CoV-2 positive, N (%) Adjusted VE (95% CI)

Pfizer, 1 dose (partial series; ages 3–4 years)

July 4, 2022–April 8, 2023

Unvaccinated 23,376 6,381 (27) Ref

1 monovalent dose (2 weeks–1 month)* 448 114 (25) 20 (0 to 36)

Pfizer, 2 doses (partial series; ages 3–4 years)

July 25, 2022–April 8, 2023

Unvaccinated 18,492 4,469 (24) Ref

2 monovalent doses (2 weeks–3 months)* 951 140 (15) 40 (28 to 50)

Pfizer, 3 doses (complete series; ages 3–4 years)**September 19, 2022–April 8, 2023

Unvaccinated 8,610 1,445 (17) Ref

3 monovalent doses (2 weeks–6 months)* 478 64 (13) 27 (4 to 45)

-20 0 20 

Vaccine 
 Vaccine coverage is low in children aged ≤5 years. VE estimates may be le

vaccine coverage is low. 

 Prevalence of prior infection in children is high*; consequently, VE in this 

the current situation among young children in the United States.

 Low vaccination coverage in this age group may impact future ability to e

including against more severe outcomes.

 The goal of the U.S. COVID-19 vaccination program is to prevent severe d

VE against symptomatic infection provides important insight into vaccine especially before VE estimates for key questions are available.

Limitations*https://covid.cdc.gov/covid-data-tracker/#pediatric-seroprevalence; 92% seroprevalence in children 6 months -17 years nationall
 Complete monovalent primary series vaccination helped provide pro

children aged 3–5 years against symptomatic SARS-CoV-2 infection fo

first 3 months after vaccination.

 Waning of monovalent Moderna primary series appears to occur by 4

after the second dose.

 Initial protection and waning patterns are similar to those observed i

and adults in the first months after vaccination. 

 Waning of monovalent Pfizer-BioNTech VE against symptomatic infec

be assessed but is also likely based on analyses in older children and 

 Children should stay up to date with COVID-19 vaccines. CDC will continue to monitor VE in this age group, including against s

and for bivalent doses.

Conclusions
Updated estimates of bivalent VE again

emergency department/urgent care enand hospitalizations among adults aged years, VISION Network

Updated analyses based on: Tenforde MW, Weber ZA, Natarajan K, et al. Early Estimates of Bivalent mRNA Vaccine Effectiveness in Preventin

Associated Emergency Department or Urgent Care Encounters and Hospitalizations Among Immunocompetent Adults — VISION Network, NiNovember 2022. MMWR Morb Mortal Wkly Rep 2023;71:1637–1646. DOI: http://dx.doi.org/10.15585/mmwr.mm7153a1
VISION Multi-State Network of Electronic Health Rec

 Variant periods desi

analysis based on timsublineage became study site

 VE adjusted for age, 

ethnicity, geographic calendar time, and lSARS-CoV-2 circulati

 Vaccination docume

electronic health recand city registries

 Cases: COVID-like illness (CLI) with 

positive PCR for SARS-CoV-2 within 14 days before or 72 hours after the admission or encounter

 Controls: CLI with negative PCR for SARSCoV-2 
VISION: Absolute VE of monovalent and bivalent booster again

encounters among immunocompetent adults aged ≥18 years, b

September 2022 – March 2023**Unpublished CDC data. 

mRNA Dosage Pattern Total tests SARS-CoV-2- test-positive, N (%) Median interval since last dose, days (IQR) Adjusted VE (95% CI)

Aged 18-64 years

Unvaccinated (ref) 55,418 5,699 (10) -- Ref

Monovalent doses only, last dose ≥2 months earlier 81,766 8,518 (10) 391 (311-518) 4 (0-7)Bivalent booster, 7-59 days earlier 6,744 399 (6) 33 (20-46) 53 (48-58)Bivalent booster, 60-119 days earlier 5,834 428 (7) 84 (71-100) 42 (35-47)Bivalent booster, 120-179 days earlier 2,352 243 (10) 139 (129-153) 15 (2-26)

Aged ≥65 years

Unvaccinated (ref) 10,559 1,833 (17) -- Ref

Monovalent doses only, last dose ≥2 months earlier 42,019 5,721 (14) 343 (215-441) 20 (15-25)Bivalent booster, 7-59 days earlier 9,103 724 (8) 35 (21-47) 61 (57-64)Bivalent booster, 60-119 days earlier 9,086 935 (10) 86 (73-101) 47 (42-52)Bivalent booster, 120-179 days earlier 3,857 483 (13) 139 (129-153) 25 (16-34)

0 
VISION: Absolute VE of monovalent and bivalent booster again

hospitalization among immunocompetent adults aged ≥18 yea

group – September 2022 – March 2023**Unpublished CDC data. **Not included due to imprecise estimates (confidence intervals >50 percentage points). 

mRNA Dosage Pattern Total tests SARS-CoV-2- test-positive, N (%) Median interval since last dose, days (IQR) Adjusted VE (95% CI)

Aged 18-64 years

Unvaccinated (ref) 7,126 565 (8) -- Ref

Monovalent doses only, last dose ≥2 months earlier 9,621 659(7) 388 (300-522) 21 (10-30)Bivalent booster, 7-59 days earlier 839 28 (3) 33 (21-46) 68 (53 to 79)Bivalent booster, 60-119 days earlier 746 56 (8) 84 (70-101) 27 (2 to 46)Bivalent booster, 120-179 days earlier 268 21 (8) 137 (128-150) **

Aged ≥65 years

Unvaccinated (ref) 6,687 1,132 (17) -- Ref

Monovalent doses only, last dose ≥2 months earlier 20,474 2,735 (13) 354 (232-460) 25 (18 to 31)Bivalent booster, 7-59 days earlier 3,494 264 (8) 35 (21-47) 64 (59 to 69)Bivalent booster, 60-119 days earlier 3,561 358 (10) 86 (73-102) 53 (46 to 59)Bivalent booster, 120-179 days earlier 1,472 158 (11) 139 (128-152) 39 (26 to 50)

0 
VISION: Absolute VE of bivalent booster against hospitalization 

immunocompromised adults aged ≥18 years –September 2022 – March 2023**Unpublished CDC data. 

mRNA Dosage Pattern Total tests SARS-CoV-2- test-positive, N (%) Median interval since last dose, days (IQR) Adjusted VE (95% CI)

Unvaccinated (ref) 2,763 295 (11) -- Ref

Monovalent doses only, last dose ≥2 months earlier 9,232 977 (11) 343 (225-452) 5 (-10 to 18)Bivalent booster, 7-59 days earlier 1,518 134 (9) 33 (19-46) 30 (12 to 44)Bivalent booster, 60-119 days earlier 1,610 125 (8) 87 (73-102) 43 (28 to 55)Bivalent booster, 120-179 days earlier 723 59 (8) 139 (129-152) 31 (4 to 50)

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Characteristics of patients with COVID-19-associated hospitalizatio

Network, 10 States, October 29, 2022–March 29, 2023

Characteristic

All hospitalizationsN=9499

CN

Age, median (IQR), years 75 (65–84) 74 Female sex, No. (%) 4818 (50.7) 88No. of categories of underlying medical conditions, median (IQR)** 3 (2–4) 4 Immunocompromising condition, No. (%) 1677 (17.7) 43

COVID-19 vaccination status, No. (%)

Unvaccinated 2842 (29.9) 6

Complete primary series 2273 (23.9) 4Primary series + 1 booster dose 2388 (25.1) 4Primary series + 2 booster doses 1320 (13.9) 2Primary series + 3 booster doses 668 (7.0) 9Primary series + 4 booster doses 8 (0.1) 3 

Received mRNA bivalent dose*** 1567 (16.5) 2

*Admitted to an intensive care unit and/or in-hospital death.**Categories of underlying medical conditions include pulmonary, cardiovascular, cerebrovascular, neurological or musculoskeletal, endocrine or metabolic, h

***Any mRNA vaccine doses received on or after September 2, 2022 were considered to be bivalent.Note: this analysis includes recipients of mRNA or Janssen primary series
Updated estimates of bivalent VE again

hospitalizations among adults aged ≥65 

IVY Network

Updated analyses based on: Surie D, DeCuir J, Zhu Y, et al. Early Estimates of Bivalent mRNA Vaccine Effectiveness in Preventing COVID-19–A

Hospitalization Among Immunocompetent Adults Aged ≥65 Years — IVY Network, 18 States, September 8–November 30, 2022. MMWR Mor2022;71:1625–1630. DOI: http://dx.doi.org/10.15585/mmwr.mm715152e2
IVY Network — 25 hospitals, 20 U.S. States

 Design: Prospective, case-control Period: September 8, 2022–April 1, 2023 Population: Adults aged ≥18 years hospitalized 

with COVID-like illness (CLI)*

 Cases: CLI and test positive for SARS-CoV-2 by RTPCR or antigen test within 10 days of illness Controls: CLI and test negative for SARS-CoV-2 and 

influenza by RT-PCR within 10 days of illness

 VE adjustments: Age, sex, race and ethnicity, 

admission date (biweekly), and HHS region

*COVID-like illness (CLI) is defined as presence of any one of the following: fever, cough, shortness of breath, chest imaging consistent with pneumonia, new or worse
Absolute and relative VE against COVID-19 hospitalizations

among immunocompetent adults aged ≥65 years — IVY Network, September 8, 2022 – April 1, 2023

Vaccinated cases, 

no./total no. (%)

Vaccinated 

controls, 

no./total no. (%)

Median time

since last dose,

days (IQR)

Adjusted VE,

% (95% CI)

Absolute VEUnvaccinated (Ref) -- Monovalent doses only, last dose 

≥2 months earlier 783/997 (79) 884/1101 (80) 373 (259–476) 13 (-9 to 30)

Bivalent booster dose, 7–59 days earlier 61/275 (22) 175/392 (45) 34 (19–49) 65 (49–77)Bivalent booster dose, 60–119 days earlier 105/319 (33) 183/400 (46) 89 (73–103) 43 (17–60) Bivalent booster dose, 120–179 days earlier 73/287 (25) 92/309 (30) 141 (129–154) 22 (-26 to 52)

Relative VE

Monovalent doses only, last dose 

≥2 months earlier (Ref)

Bivalent booster dose, 7–59 days earlier 61/844 (7) 175/1059 (17) 34 (19–49) 60 (45–71) Bivalent booster dose, 60–119 days earlier 105/888 (12) 183/1067 (17) 89 (73–103) 35 (14–51) Bivalent booster dose, 120–179 days earlier 73/856 (9) 92/976 (9) 141 (129–154) 17 (-21 to 42)

-40 
Estimates of monovalent VE against inv

mechanical ventilation and death amonaged ≥18 years, IVY Network
IVY: Effectiveness of 2-4 monovalent mRNA COVID-19 vaccine 

COVID-19 invasive mechanical ventilation or death among 

immunocompetent adults aged ≥18 years — IVY Network, FebJanuary 31, 2023

Vaccinated cases,

no./total no. (%)

Vaccinated 

controls, 

no./total no. (%)

Median time

since last 

dose,

days (IQR)

Absolute 

adjusted VE,

% (95% CI)

Overall 216/362 (60) 3080/4059 (76) 248 (138–378) 62 (52–70)

Age group, yrs -- 18–64 85/163 (52) 1421/2095 (68) 263 (144–380) 57 (39–70)

≥65 131/199 (66) 1659/1964 (84) 238 (133–375) 69 (57–78)

Time since last dose to illness, days

7–179 63/209 (30) 1112/2091 (53) 109 (68–145) 76 (66–83)

180–364 95/241 (39) 1110/2089 (53) 269 (220–317) 54 (37–66)≥365 58/204 (28) 858/1837 (47) 455 (402–549) 56 (36–69)

-20 0 
Effectiveness of monovalent mRNA COVID-19 vaccines against 

invasive mechanical ventilation or death among immunocompaged ≥18 years — IVY Network, February 1, 2022 – January 31

Vaccinated cases,

no./total no. (%)

Vaccinated 

controls, 

no./total no. (%)

Median time

since last 

dose,

days (IQR)

Absolute 

adjusted VE,

% (95% CI)

Time since last dose to illness, by no. of doses received7–179 days before illness

2 doses 6/152 (4) 108/1087 (10) 114 (72–153) –*

3 doses 42/188 (22) 633/1612 (39) 116 (75–147) 70 (55–81)4 doses§ 15/91 (17) 353/860 (41) 94 (55–135) 84 (69–92)

≥180 days before illness

2 doses 81/227 (36) 953/1932 (49) 418 (326–531) 50 (32–64)

3 doses 66/212 (31) 901/1880 (48) 292 (235–366) 59 (42–72)4 doses§ 4/80 (5) 108/615 (18) 223 (197–258) –*

*VE estimate not reported because of insufficient sample size§Logistic regression models for VE of 4 monovalent doses were restricted to patients aged ≥50 years admitted during April 5, 2022–January 31, 2023

0 2

V
 For estimates of absolute vaccine effectiveness, if unvaccinated are m

different from vaccinated individuals (e.g., by COVID-19 risk factors), ebe biased.

 For estimates of relative vaccine effectiveness, residual protection fro

an important consideration.

 Information on prior infection is limited, although we know rates of pr

the U.S. population are high. 

 VE against COVID-19-associated hospitalization may underestimate pro

against more severe COVID-19 disease.

Limitations of VE against severe disease
 Bivalent boosters are helping provide additional protection agains

department/urgent care encounters and hospitalization, though ewaning

 For most people who received monovalent doses and are eligible 

booster, more than a year has elapsed since their last monovalent of waning, they may have limited remaining protection.

 Vaccines provide durable protection against the most critical illne

ventilation and death)

 CDC will continue ongoing monitoring of VE, including for all outc

and for all authorized vaccines in the U.S. (Pfizer-BioNTech, ModeNovavax) with a focus on assessing new policy recommendations populations at higher risk of severe COVID-19

Conclusions: updates to VE of bivalent COVID-19 
CDC COVID-19 Vaccine Effectiveness and 

Policy Team Amadea Britton Allison Ciesla Monica Godfrey Eric Griggs Katherine Fleming-Dutra Morgan Najdowski Sara Oliver Amanda Payne Lauren Roper Laura Steinhardt Evelyn Twentyman Megan Wallace Ryan Wiegand

VE platforms teams, includi

 Sarah Ball Jennifer DeCuir Monica Dickerson Margaret Dunne Matthew Levy Patrick Mitchell Palak Patel Caitlin Ray

And many more!!!

Acknowledgements

 S Z D Z M
For more information, contact CDC

1-800-CDC-INFO (232-4636)TTY: 1-888-232-6348 www.cdc.govThe findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for DPhotographs and images included in this presentation are licensed solely for CDC/NCIRD online and presentation use. No rights are implied oany use by other CDC CIOs or any external audiences.