cdc.gov/coronavirus

Epidemiology of COVID-19-Associated Hospitalizations, 

including in Pregnant Persons and Infants

Fiona Havers, MD, MHS, FIDSA

Team Lead, RESP-NET Hospitalization Surveillance Team

Commander, US Public Health Service

Coronavirus and Other Respiratory Viruses Division

National Center for Immunization and Respiratory Diseases

Centers for Disease Control and Prevention

Advisory Committee on Immunization Practices

June 23, 2023
COVID-19-associated hospitalizations

COVID-NET: March 2020 – June 2023
COVID-NET Hospitalizations

▪ >250 acute-care hospitals

▪ 98 counties in 13 states

▪ ~10% of U.S. population

▪ Positive SARS-CoV-2 within 14 days of or 

during hospitalization

▪ Screening or clinician-driven testing

▪ Clinical data is from representative sample 

of COVID-NET patients

3
Weekly COVID-19-associated hospitalization rates — COVID-NET, 14 U.S. 

States

Rates highest in ≥75 years, 

followed by infants <6 months and 

those 65 – 74 years

0

20

40

60

80

100

120

140

March 1, 2020 – June 3, 2023

0-<6 months 6 months-4 years 5-11 years 12-17 years

18-49 years 50-64 years 65-74 years ≥ 75 years

0

20

40

60

80

100

120

140

7-Jan 7-Feb 7-Mar 7-Apr 7-May

January 1 – June 3, 2023

4
COVID-19-associated hospitalization rates by race and ethnicity* —

COVID-NET, 14 U.S. States, October 2022 – May 2023

* Black, White, American Indian/Alaska Native and Asian/Pacific Islander people 

were categorized as non-Hispanic; Hispanic people could be of any race. 

Cumulative hospitalization rates 

remain highest in American 

Indian/Alaska Native and Black 

persons

0

50

100

150

200

250

300

Hospitalization Rate per 100,000

Age adjusted cumulative rates 

October 2022 – May 2023

0

2

4

6

8

10

12

14

16

Rate per 100,000

Age adjusted 3-week moving average rate 

January – May 2023

Hispanic American Indian/Alaska Native Asian/Pacific Islander Black White

5
COVID-19-associated hospitalizations in 

pregnant persons

COVID-NET: January 2021 – April 2023
COVID-19-associated hospitalizations among pregnant persons aged 15–

49 years — COVID-NET, 14 U.S. States, January 2021–April 2023

Most pregnant people 

hospitalized with a positive SARSCoV-2 test had no respiratory 

symptoms

• 363 of 1,651 (21%) had respiratory 

symptoms recorded

• Proportion without respiratory 

symptoms increased from 73% to 82%

Among symptomatic patients, 

the proportion with underlying 

medical conditions increased

January –

November 2021

(pre-Omicron)

N (%)

December 2021 –

June 2022

(early Omicron)

N (%)

July 2022 – April 

2023

(later Omicron)

N (%)

Total number 184 99 80

Age group

15-24 years 45 (16) 38 (31) 22 (21)

25-34 years 98 (60) 46 (54) 45 (59)

35-49 years 41 (25) 15 (15) 13 (20)

Any underlying 

medical conditions 72 (33) 32 (33) 46 (56)

Any pregnancyassociated 

complications*

37 (20) 25 (31) 23 (29)

Table 1. Characteristics of COVID-19-associated hospitalized pregnant 

patients (15–49 years) with respiratory symptoms

*Pregnancy-associated complications include hypertensive disorders of pregnancy, 

gestational diabetes, intrauterine growth restrictions, and pre-eclampsia. Note that 

percentages are weighted to account for sampling scheme. 7
January –

November 2021

(pre-Omicron)

N (%)*

December 2021 

– June 2022

(early Omicron)

N (%)*

July 2022 – April 

2023

(later Omicron)

N (%) *

Total Number 184 99 80

Interventions

High flow nasal 

cannula 20 (12) 2 (2) 0 (0)

BIPAP/CPAP 5 (2) 1 (1) 1 (3)

Mechanical 

ventilation 15 (7) 3 (2) 1 (2)

Vasopressor 26 (15) 3 (2) 3 (6)

Dialysis or RRT 1 (0.5) 1 (1) 0 (0)

Severe outcomes

ICU admission 31 (17) 7 (6) 2 (4)

In-hospital death 0 (0) 1 (1) 0 (0)

Interventions and outcomes among pregnant patients with respiratory 

symptoms and a positive SARS-CoV-2 test

The proportion 

requiring ICU 

admission and 

vasopressor support 

decreased over time

*Note that percentages are weighted to account for sampling scheme. 8
0

10

20

30

40

50

60

70

80

90

100

Unvaccinated Primary

series only

Primary 

series + ≥ 1 

booster

Unvaccinated Primary

series only

Primary 

series + ≥ 1 

booster

Unvaccinated Primary

series only

Primary 

series + ≥ 1 

booster

January-November 2021 (n=1,231) December 2021-June 2022 (n=279) July 2022-January 2023 (n=239)

Weighted %

Respiratory symptoms No COVID-19 symptoms recorded

Vaccination status among pregnant patients hospitalized with 

laboratory-confirmed SARS-CoV-2 infection by symptom status, COVIDNET, January 2021–April 2023

More asymptomatic 

pregnant patients 

received boosters 

compared with 

symptomatic 

patients

Most pregnant 

patients had not 

received booster 

doses

9
COVID-19-associated hospitalizations in 

infants <6 months

COVID-NET: March 2020 – May 2023
Infants <6 months old had similar COVID-19–associated 

hospitalization rates to adults aged 65–74 years old

Source: COVID-NET: https://www.cdc.gov/coronavirus/2019-ncov/covid-data/covid-net/purpose-methods.html. Data March 1, 2020 through March 31, 2023. Pre-Delta: March 1, 2020 –

June 19, 2021; Delta: June 20–December 18, 2021; Omicron BA.1: December 19, 2021–March 19, 2022; Omicron BA.2: March 20–June 18, 2022; Omicron BA.5 (June 19, 2022–June 3, 2023)

Pre-Delta Delta

Omicron

BA.1

Omicron

BA.2 Omicron BA.5 and later

11

0

20

40

60

80

100

120

140

160

Hospitalization rate per 100,000

0-<6 months 6 months-4 years 5-11 years 12-17 years 65-74 years ≥ 75 years
Hospitalization rates in infants, children and adolescents 

aged 6 months through <18 years

Source: COVID-NET: https://www.cdc.gov/coronavirus/2019-ncov/covid-data/covid-net/purpose-methods.html. Data March 1, 2020 through March 31, 2023. Pre-Delta: March 1, 2020 – June 

19, 2021; Delta: June 20–December 18, 2021; Omicron BA.1: December 19, 2021–March 19, 2022; Omicron BA.2: March 20–June 18, 2022; Omicron BA.5 (June 19, 2022–May 27, 2023)

Pre-Delta Delta

Omicron

BA.1

Omicron

BA.2 Omicron BA.5 and later

0

2

4

6

8

10

12

14

16

18

20

3/7/20204/7/20205/7/20206/7/20207/7/20208/7/20209/7/2020

10/7/202011/7/202012/7/2020

1/7/20212/7/20213/7/20214/7/20215/7/20216/7/20217/7/20218/7/20219/7/2021

10/7/202111/7/202112/7/2021

1/7/20222/7/20223/7/20224/7/20225/7/20226/7/20227/7/20228/7/20229/7/2022

10/7/202211/7/202212/7/2022

1/7/20232/7/20233/7/20234/7/20235/7/2023

Rate per 100,000

6 months <2 years 2-4 years 5-11 years 12-17 years

12
On average, 15% of hospitalized infants <6 months with 

COVID-19 were identified during their birth hospitalization*

*Birth hospitalization was defined as admission date within 1 day of birth. Source: COVID-NET: https://www.cdc.gov/coronavirus/2019-ncov/covid-data/covid-net/purpose-methods.html. Data March 1, 2020 

through March 31, 2023. Pre-Delta: March 1, 2020 – June 19, 2021; Delta: June 20–December 18, 2021; Omicron BA.1: December 19, 2021–March 19, 2022; Omicron BA.2: March 20–June 18, 2022; Omicron 

BA.5 (June 19, 2022–March 31, 2023) . 

18 16 16 20

11

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Pre-Delta Delta Omicron BA.1 Omicron BA.2 Omicron BA.5 and later

Birth hospitalization Separate hospitalization

13
95% of infants <6 months old with a separate hospitalization 

had COVID-19 symptoms during the Omicron BA.5 period

Source: COVID-NET: https://www.cdc.gov/coronavirus/2019-ncov/covid-data/covid-net/purpose-methods.html. Data March 1, 2020 through March 31, 2023. Pre-Delta: March 1, 2020 – June 19, 

2021; Delta: June 20–December 18, 2021; Omicron BA.1: December 19, 2021–March 19, 2022; Omicron BA.2: March 20–June 18, 2022; Omicron BA.5 (June 19, 2022–March 31, 2023)

93 94 94 97 95

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Pre-Delta Delta Omicron BA.1 Omicron BA.2 Omicron BA.5 and

later

Symptoms No symptoms

14
1 in 5 infants < 6 months old with COVID-19 were admitted to 

the ICU (excluding birth hospitalizations)

Source: COVID-NET: https://www.cdc.gov/coronavirus/2019-ncov/covid-data/covid-net/purpose-methods.html. Data March 1, 2020 through March 31, 2023. Pre-Delta: March 1, 2020 – June 

19, 2021; Delta: June 20–December 18, 2021; Omicron BA.1: December 19, 2021–March 19, 2022; Omicron BA.2: March 20–June 18, 2022; Omicron BA.5 (June 19, 2022–March 31, 2023)

19%

5%

2% 2%

0.3%

18%

14%

4%

5%

0.0%

24%

15%

8%

3%

1%

21%

14%

5% 4%

2%

20%

19%

3%

6%

0%

0%

5%

10%

15%

20%

25%

30%

ICU admission High flow nasal cannula Invasive mechanical

ventilation

BiPAP or CPAP use In-hospital death

WEIGHTED % OF COVID-19-ASSOCIATED HOSPITALIZATIONS

Pre-delta

Delta

Omicron BA.1

Omicron BA.2

Omicron BA.5 and later

15
• General: Hospitalization rates decreased in all age groups

• The age distribution of persons hospitalized with COVID-19 has shifted such that the highest 

rates are in adults aged ≥75 years followed by those 65-74 years and infants ages <6 months

• Pregnant persons: 

• Most pregnant persons hospitalized with a positive SARS-CoV-2 test had no symptoms 

recorded at admission and were likely identified through screening on admission

• Among those with respiratory symptoms, the proportion with underlying medical conditions 

has increased and the proportion with severe outcomes has decreased

• Most hospitalized pregnant persons with a positive SARS-CoV-2 test, regardless of symptoms 

or reason for testing, were not up to date with vaccinations

• Infants <6 months: Hospitalization rates increased in the Omicron period 

• Most hospitalized with COVID-19-like symptoms 

• Excluding birth hospitalizations, 20% admitted to the ICU since June 2022

Trends in COVID-19-associated hospitalizations – COVID-NET, March 2020 

– May 2023

16
Acknowledgments

Coronaviruses and Other Respiratory 

Viruses Division (CORVD):

RESP-NET Team (COVID-NET/RSV-NET):

• Michael Whitaker

• Kadam Patel

• Christopher Taylor

• Huong Pham

• Onika Anglin

• Jenny Milucky

• Bhoomija Chatwani

• Michael Melgar

• Monica Patton

Many others in CORVD....

▪ State, Local, and Territorial 

health Department partners

▪ RESP-NET partners

Thank you.
Centers for Disease Control and Prevention

COVID-19 in pregnant people

Romeo Galang, MD MPH

Emergency Preparedness and Response Team

Field Support Branch

Division of Reproductive Health

National Center for Chronic Disease Prevention and Health Promotion
Disease burden and risks to 

maternal and infant health
COVID-19 in Pregnant People

▪ COVID-19 during pregnancy is associated with more severe maternal 

health outcomes

▪ COVID-19 during pregnancy is associated with adverse pregnancy 

outcomes (e.g., preterm birth, stillbirth)

▪ Adverse maternal, fetal, and infant outcomes differed according to the 

circulating variant
Reported COVID-19 cases overall and among pregnant people in the US

(National COVID-19 Case Surveillance Data; Jan 22, 2020–May 3, 2023)

Total among 

pregnant people: 

226,263 cases

738 ICU admissions

329 Deaths 

0

5000

10000

15000

20000

25000

30000

Overall Cases

Cases among 

pregnant 

people

Pre-Delta Delta Omicron 
Among people with COVID-19, pregnancy increased the risk for ICU 

admission and invasive ventilation

(Living Systematic Review with data from 1 Dec 2019 - 27 Apr 2021)

Outcomes # Studies

# with event/# in group (%)

Odds ratio (95% CI)

Pregnant with COVID -19 Non-pregnant with 

COVID-19

All cause mortality 11 242/122 222 (0.2) 5252/2 138 726 (0.2) 1.48 (0.62 to 3.49)

ICU admission 10 912/118 403 (0.8) 11 513/1 908 957 (0.6) 2.61 (1.84 to 3.71)

Invasive ventilation 8 310/116 458 (0.3) 3607/1 772 716 (0.2) 2.41 (2.13 to 2.71)

ECMO 5 19/30 694 (0.1) 122/432 623 (0.0) 3.71 (0.71 to 19.41)

ARDS 4 22/197 (11.2) 45/418 (10.8) 1.19 (0.24 to 5.95)

Major organ failure 4 5/197 (2.5) 28/418 (6.7) 0.39 (0.15 to 1.04)

Allotey, J et al. Clinical manifestations, risk factors, and maternal and perinatal outcomes of coronavirus disease 2019 in pregnancy: living systematic review and metaanalysis. BMJ. 2020. Final version 7-May 2022 https://doi.org/10.1136/bmj.m3320

ECMO: extracorporeal membrane oxygenation; ARDS: Acute respiratory distress syndrome
Among pregnant people, COVID-19 increased the risk for adverse 

maternal, fetal, and infant outcomes 

(Living Systematic Review with data from 1 Dec 2019 - 27 Apr 2021)

Outcomes # Studies

# with event/# in group (%)

Odds ratio (95% CI)

Pregnant with COVID-19 Pregnant without 

COVID-19

Maternal outcomes:

All cause mortality 21 47/11 362 (0.4) 37/411 126 (0.0) 6.09 (1.82 to 20.38)

ICU admission 21 447/12 957 (3.4) 1962/459 359 (0.4) 5.41 (3.59 to 8.14)

Preterm birth <37 weeks 48 1306/12 076 (10.8) 26 068/436 964 (6.0) 1.57 (1.36 to 1.81)

Perinatal outcomes:

Stillbirth 25 76/9338 (0.8) 1397/414 139 (0.3) 1.81 (1.38 to 2.37)

Neonatal death 21 16/3153 (0.5) 28/9 263 (0.3) 2.35 (1.16 to 4.76)

Admission to neonatal unit 29 687/4072 (16.9) 6968/193 124 (3.6) 2.18 (1.46 to 3.26)

Fetal distress 6 131/1073 (12.2) 246/3933 (6.3) 2.22 (1.45 to 3.41)

Allotey, J et al. Clinical manifestations, risk factors, and maternal and perinatal outcomes of coronavirus disease 2019 in pregnancy: living systematic review and metaanalysis. BMJ. 2020. Final version 7-May 2022 https://doi.org/10.1136/bmj.m3320
Pregnancy-related mortality increased rapidly in 2021 (pre-Omicron), 

consistent with rising rates of COVID-19 associated mortality

Thoma, M. E., & Declercq, E. R. (2023). Changes in Pregnancy-Related Mortality Associated With the Coronavirus Disease 2019 (COVID-19) Pandemic in the United States. Obstetrics and gynecology, 141(5), 

911–917. https://doi.org/10.1097/AOG.0000000000005182
Have risks evolved by COVID-19 variant?
Figure 1. Maternal deaths and maternal deaths mentioning 

COVID-19, by count, US 2020-2022

Pre-delta Delta Omicron

Note: Data for 2020-2021 are final and data for 2022-2023. Death counts between 1-9 are suppressed in accordance with NCHS confidentiality standards. Weeks with COVID-19 death counts 1-9 are noted on the figure with 

black and grey diagonal lines.

Source: CDC, National Center for Health Statistics. National Vital Statistics System, Provisional Mortality on CDC WONDER Online Database. Accessed at http://wonder.cdc.gov/mcd-icd10-provisional.html 

0

20

40

60

80

100

120

140

160

180

200

Number of Deaths

Date of Death

Maternal Deaths without COVID-19 Maternal Deaths with COVID-19 Counts 1-9
Updated Premier: Pregnant Person Complications Associated With a 

Documented COVID-19 Diagnosis at Delivery Hospitalization—

United States, Pre-delta, Delta, and Omicron

Ko et al., 2021 (n = 489471)

June 2021-December 2021 (n=505108)

2022 (n = 782503)

*Data from Delta and 

Omicron periods are 

unpublished
Updated Premier: Pregnant Person Complications Associated With a 

Documented COVID-19 Diagnosis at Delivery Hospitalization—

United States, Pre-delta, Delta, and Omicron

Ko et al., 2021 (n = 489471)

June 2021-December 2021 (n=505108)

2022 (n = 782503)

Although less than Delta, 

risks remain elevated 

during Omicron

*Data from Delta and 

Omicron periods are 

unpublished
Updated Premier: Pregnant Person Complications Associated With a 

Documented COVID-19 Diagnosis at Delivery Hospitalization—

United States, Pre-delta, Delta, and Omicron

*Data from Delta and 

Omicron periods are 

unpublished

Ko et al., 2021 (n = 489471)

June 2021-December 2021 (n=505108)

2022 (n = 782503)
Updated Premier: Pregnant Person Complications Associated With a 

Documented COVID-19 Diagnosis at Delivery Hospitalization—

United States, Pre-delta, Delta, and Omicron

Ko et al., 2021 (n = 489471)

June 2021-December 2021 (n=505108)

2022 (n = 782503)

*Data from Delta and 

Omicron periods are 

unpublished

Similar pattern: Although less than Delta, 

increased risks persisted during Omicron
Updated Premier: Pregnant Person Complications Associated With a 

Documented COVID-19 Diagnosis at Delivery Hospitalization—

United States, Pre-delta, Delta, and Omicron

Ko et al., 2021 (n = 489471)

June 2021-December 2021 (n=505108)

2022 (n = 782503)

*Data from Delta and 

Omicron periods are 

unpublished

Similar pattern: Although less than Delta, 

increased risks persisted during Omicron
Adverse Pregnancy Outcomes Associated With a Documented COVID19 Diagnosis at Delivery Hospitalization—United States, 

Pre-delta, Delta, and Omicron Periods, Premier

Ko et al., 2021 (n = 489471)

June 2021-December 2021 (n=505108)

2022 (n = 782503)

*Data from Delta and 

Omicron periods are 

unpublished
Adverse Pregnancy Outcomes Associated With a Documented COVID19 Diagnosis at Delivery Hospitalization—United States, 

Pre-delta, Delta, and Omicron Periods, Premier

Ko et al., 2021 (n = 489471)

June 2021-December 2021 (n=509265)

2022 (n = 765425)

*Data from Delta and 

Omicron periods are 

unpublished

• Although less than Delta, risks 

for adverse pregnancy 

outcomes and preterm delivery 

remain elevated during Omicron

• Risk for stillbirth not 

significantly elevated during 

Omicron
Trends (%) in pregnancy outcomes by maternal COVID-19 status: 

14 states and the District of Columbia (July 2020-December 2022)

pre-Delta

July 2020-June 2021

Delta

July 2021 - December 2021

Omicron

January 2022 - December 2022

COVID-191 No COVID-19 COVID-191 No COVID-19 COVID-191 No COVID-19

ICU admission 0.6 0.1 1.2 0.2 0.2 0.2

NICU admission 10.3 8.7 10.9 8.5 9.0 8.7

Total preterm2 11.9 9.9 13.0 10.1 10.3 10.1

Early preterm 3.2 2.6 3.8 2.7 2.4 2.7

Late preterm 8.8 7.2 9.2 7.4 7.9 7.4

Total low birthweight3 8.8 7.9 9.8 8.1 7.9 8.2

Very low birthweight4 1.5 1.3 1.6 1.3 1.1 1.3

1 Confirmed or presumed COVID-19 during pregnancy. Confirmed cases only are included for California, Maryland, Ohio, North Dakota, and Tennessee.

2 Gestational age in completed weeks; based on the obstetric estimate of gestation.

3 Less than 2,500 grams

4 Less than 1,500 grams

NOTES: Reporting area includes Alabama, Alaska, Arkansas, California, District of Columbia, Idaho, Maine, Maryland, New Hampshire, North Dakota, Ohio, Oklahoma, Oregon, Tennessee, and West Virginia. District of Columbia did not report for October-December 

2022.

SOURCE: National Center for Health Statistics, National Vital Statistics System, Natality.

https://www.cdc.gov/nchs/data/health_policy/trends-in-outcomes.pdf
Summary

▪ Incidence of COVID-19 among pregnant people mirrors that of the general 

population

▪ Pregnancy remains a risk factor for severe maternal disease and adverse 

pregnancy outcomes, even with new variants

▪ Some maternal, fetal, and infant risks were lower with Omicron; cannot 

disentangle the impact of prior infection/vaccination
Conclusion

COVID-19 vaccination improves outcomes for pregnant 

people, their pregnancies and their infants; therefore 

vaccination should continue to be recommended for maternal 

and fetal benefit
For more information, contact CDC

1-800-CDC-INFO (232-4636)

TTY: 1-888-232-6348 www.cdc.gov

The findings and conclusions in this report are those of the authors and do not necessarily represent the 

official position of the Centers for Disease Control and Prevention.

National Center for Immunization and Respiratory Diseases

Sascha Ellington

Katherine Fleming-Dutra

Sara Oliver

Regina Simeone

National Center for Health Statistics

Donna Hoyert

Joyce Martin

Michelle Osterman

Claudia Valenzuela

Acknowledgements

National Center on Birth Defects and Developmental Disorders

Jeffrey Carlson

Amanda Cohn

Dana Meaney-Delman

Suzanne Gilboa

Kara Polen

Emily Reeves

Van Tong

Kate Woodworth
Centers for Disease Control and Prevention

National Center for Immunization and Respiratory Diseases

Photographs 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 other CDC CIOs or any external audiences.

COVID-19 vaccine effectiveness updates

23 June 2023

Ruth Link-Gelles, PhD, MPH

LCDR, US Public Health Service

COVID-19 Vaccine Effectiveness Program Lead

Centers for Disease Control and Prevention
Coverage / Age (years) <2 2–4 5–11 12–17 18–24 24–49 50–64 >65

At least one dose† 8.9 10.9 40.0 72.2 82.3 85.5 95.0 95.0

At least one bivalent dose 0.6 0.6 4.8 7.8 7.4 12.1 21.7 43.3

Unvaccinated 91.1 89.1 60.0 27.8 17.7 14.5 —† —†

U.S. COVID-19 Vaccination Coverage (%) of Total Population by 

Age Group — May 10, 2023

†Note: Coverage is capped at 95%

Source: https://covid.cdc.gov/covid-data-tracker/#vaccination-demographics-trends Updated June 1, 2023 39
▪ Bivalent VE, by outcome and Omicron subvariant in adults

▪ VE in special populations:

– Monovalent and bivalent VE in pregnant people

– Bivalent people with immunocompromising conditions

Organization of vaccine effectiveness (VE) data

40
Monovalent and bivalent VE, against 

hospitalization and critical illness by Omicron 

subvariant in adults ≥18 years, VISION Network
VISION Multi-State Network of Electronic Health Records

▪ Variant periods designated for analysis 

based on time when novel sublineage 

became predominant (>50%) at study 

site

▪ VE adjusted for age, sex, race and 

ethnicity, geographic region, and 

calendar time

▪ Vaccination documented by electronic 

health records and state and 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 SARS-CoV-2

42
VISION: Absolute VE of monovalent and bivalent booster doses against 

hospitalization and critical illness among immunocompetent adults aged 

≥18 years – September 2022 – May 2023

Critical illness defined as admission to intensive care unit or death; case-patients were persons admitted to ICU or who experienced death associated with COVID-19, and control patients were persons hospitalized without COVID-19. 

VE estimates adjusted for age, sex, race and ethnicity, geographic region, and calendar time. Updated from: Link-Gelles et al., MMWR, https://www.cdc.gov/mmwr/volumes/72/wr/mm7221a3.htm 43

mRNA Dosage Pattern

Total

tests

SARS-CoV-2-

test-positive,

N (%)

Median interval

since last dose,

days (IQR)

Adjusted VE

(95% CI)

Hospitalization

Unvaccinated (ref) 16,219 1,835 (11) -- Ref

Monovalent doses only 38,843 4,086 (11) 381 (275-513) 21 (16-26)

Bivalent booster, 7-59 days earlier 4,894 329 (7) 35 (21-47) 62 (57-67)

Bivalent booster, 60-119 days earlier 5,283 491 (9) 87 (73-103) 47 (41-53)

Bivalent booster, 120-179 days earlier 3,756 346 (9) 146 (132-161) 24 (12-33)

Critical illness

Unvaccinated (ref) 14,762 378 (3) -- Ref

Monovalent doses only 35,415 658 (2) 380 (275-514) 31 (21-40)

Bivalent booster, 7-59 days earlier 4,614 49 (1) 34 (21-47) 69 (58-77)

Bivalent booster, 60-119 days earlier 4,880 88 (2) 87 (73-103) 45 (29-58)

Bivalent booster, 120-179 days earlier 3,445 35 (1) 146 (132-161) 52 (30-67)

-20 0 20 40 60 80 100

Vaccine Effectiveness (%)
VISION: Absolute VE of monovalent and bivalent booster doses against 

hospitalization and critical illness among immunocompetent adults aged ≥18 years, 

during BA.4/5 predominance – September 2022 – January 2023

CDC unpublished data. VE estimates adjusted for age, sex, race and ethnicity, geographic region, and calendar time.

Variant predominance based on regional circulation: https://covid.cdc.gov/covid-data-tracker/#variant-proportions 44

mRNA Dosage Pattern

Total

tests

SARS-CoV-2-

test-positive,

N (%)

Median interval

since last dose,

days (IQR)

Adjusted VE

(95% CI)

Hospitalization

Unvaccinated (ref) 11,240 1,426 (13) -- Ref

Monovalent doses only 27,564 3,106 (11) 349 (238-460) 25 (19-30)

Bivalent booster, 7-89 days earlier 6,723 524 (8) 47 (28-67) 61 (56-65)

Bivalent booster, ≥90 days earlier 1,511 163 (11) 105 (96-115) 40 (28-50)

Critical illness

Unvaccinated (ref) 10,110 296 (3) -- Ref

Monovalent doses only 24,976 518 (2) 347 (236-460) 33 (21-42)

Bivalent booster, 7-89 days earlier 6,199 91 (1) 47 (28-66) 61 (50-70)

Bivalent booster, ≥90 days earlier 1,348 25 (2) 105 (96-115) 49 (21-67)

-20 0 20 40 60 80 100

Vaccine Effectiveness (%)
VISION: Absolute VE of monovalent and bivalent booster doses against 

hospitalization and critical illness among immunocompetent adults aged 

≥18 years, during XBB predominance – January – May 2023

CDC unpublished data. VE estimates adjusted for age, sex, race and ethnicity, geographic region, and calendar time.

* These interim estimates are imprecise, which might be because of a relatively small number of persons in each level of vaccination or case status. This imprecision indicates 

the actual VE may be substantially different from the point estimate shown, and estimates should therefore be interpreted with caution. Additional data accrual should increase 

precision and allow appropriate interpretation.

Variant predominance based on regional circulation: https://covid.cdc.gov/covid-data-tracker/#variant-proportions 45

mRNA Dosage Pattern

Total

tests

SARS-CoV-2-

test-positive,

N (%)

Median interval

since last dose,

days (IQR)

Adjusted VE

(95% CI)

Hospitalization

Unvaccinated (ref) 4,979 409 (8) -- Ref

Monovalent doses only 11,279 980 (9) 469 (375-605) 9 (-4 to 20)

Bivalent booster, 7-89 days earlier 1,045 60 (6) 65 (43-79) 51 (35 to 63)

Bivalent booster, 90-179 days earlier 4,654 419 (9) 139 (119-157) 20 (7 to 32)

Critical illness

Unvaccinated (ref) 4,652 82 (2) -- Ref

Monovalent doses only 10,439 140 (1) 469 (375-602) 28 (3 to 46)

Bivalent booster, 7-89 days earlier 994 9 (1) 65 (43-78) 58 (15 to 79)*

Bivalent booster, 90-179 days earlier 4282 47 (1) 139 (119-157) 48 (23 to 65)

-20 0 20 40 60 80 100

Vaccine Effectiveness (%)
Monovalent and bivalent VE against 

hospitalization among adults aged ≥18 years, 

IVY Network
IVY Network — 25 hospitals, 20 U.S. States

▪ Design: Prospective, case-control

▪ 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

– 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 pneumonia, hypoxemia
IVY Network: Absolute VE against COVID-19 hospitalization

among immunocompetent adults aged ≥18 years —September 8, 

2022 – May 29, 2023

Total Cases and 

Controls Cases (%)

Median time

since last dose,

days (IQR)

Adjusted VE*,

% (95% CI)

Absolute VE

Unvaccinated (Ref) 1286 537 (42) -- Ref

Monovalent doses only 3511 1460 (42) 393 (282–517) 16 (3 to 26)

Bivalent booster dose, 7–59 days earlier 374 100 (27) 36 (21–49) 54 (39 to 65)

Bivalent booster dose, 60–119 days earlier 443 160 (36) 89 (73–103) 34 (15 to 50) 

Bivalent booster dose, 120–179 days earlier 366 157 (43) 145 (133–159) 6 (-27 to 30)*

-40 -20 0 20 40 60 80 100

Vaccine Effectiveness (%)

* These interim estimates are imprecise, which might be because of a relatively small number of persons in each level of vaccination or case status. This imprecision indicates the actual VE may be substantially different 

from the point estimate shown, and estimates should therefore be interpreted with caution. Additional data accrual should increase precision and allow appropriate interpretation.

VE adjustments: Age, sex, race, ethnicity, admission date (biweekly), and HHS region
IVY Network: Absolute VE against COVID-19 hospitalization

among immunocompetent adults aged ≥18 years by lineage 

period — September 8, 2022 – May 24, 2023

Total Cases and 

Controls Cases (%)

Median time

since last dose,

days (IQR)

Adjusted VE*,

% (95% CI)

BA.4/5 (September 8 – November 13, 2022)

Unvaccinated (Ref) 313 138 (44) -- Ref

Monovalent doses only 1003 398 (40) 304 (188–386) 30 (8–47)

Bivalent booster dose, 7–59 days earlier 83 26 (31) 25 (13–40) 59 (21–78)*

BQ.1 (November 14, 2022 – January 22, 2023)

Unvaccinated (Ref) 458 190 (41) -- Ref

Monovalent doses only 1262 504 (40) 386 (297–518) 17 (-5 to 34)

Bivalent booster dose, 7–59 days earlier 226 52 (23) 40 (25–52) 63 (44–75)

Bivalent booster dose, 60–119 days earlier 225 68 (30) 83 (69–95) 49 (24–66)

XBB (January 23 – May 24, 2023) 

Unvaccinated (Ref) 514 209 (41) -- Ref

Monovalent doses only 1246 558 (45) 464 (378–590) -8 (-34 to 13)

Bivalent booster dose, 7–89 days earlier 155 56 (36) 64 (46–78) 29 (-8 to 53)*

Bivalent booster dose, 90–179 days earlier 478 208 (44) 137 (118–154) -8 (-44 to 19)*

* These interim estimates are imprecise, which might be because of a relatively small number of persons in each level of vaccination or case status. This imprecision indicates the actual VE may be

substantially different from the point estimate shown, and estimates should therefore be interpreted with caution. Additional data accrual should increase precision and allow appropriate interpretation.

VE adjustments: Age, sex, race, ethnicity, admission date (biweekly), and HHS region

-55 -35 -15 5 25 45 65 85

Vaccine Effectiveness (%)
VE in special populations:

pregnant people
VISION Multi-State Network of Electronic Health Records

▪ Cases: COVID-like illness (CLI) with positive PCR for 

SARS-CoV-2 within 14 days before or 72 hours after the 

encounter

▪ Controls: CLI with negative PCR for SARS-CoV-2

51

▪ Among pregnant people 18-45 years at time of 

emergency department/urgent care encounter

▪ VE adjusted for age, ethnicity, race, underlying 

medical conditions, gestational age at 

encounter, site, Medicaid status, day of 

encounter, site facility urbanicity

▪ Vaccination documented by electronic health 

records and state and city registries

▪ Separate results for COVID-19 vaccine 

monovalent doses received prior to pregnancy 

and bivalent doses received during pregnancy 

due to timing of bivalent authorization/analysis 

(Sept 2022-May 2023)
VISION: Absolute VE of COVID-19 monovalent doses received prior to

pregnancy against ED/UC encounters among immunocompetent pregnant 

persons aged 18-45 years – June 2022 – May 2023*

Adjusted for: Age, ethnicity, race, underlying medical conditions, gestational age at encounter, site, Medicaid status, day of encounter, site facility urbanicity

*Unpublished CDC data. 52

Vaccine Dosage Pattern Total

tests

SARS-CoV-2-

test-positive,

N (%)

Median interval

since last dose,

days (IQR)

Adjusted VE

(95% CI)

Absolute VE

Unvaccinated (ref) 2238 317 (14) -- Ref

Monovalent received:

<6 months before pregnancy 833 108 (13) 270 (216, 326) 27 (6, 44)

≥6 months before pregnancy 1986 264 (13) 454 (375, 544) 5 (-15, 22)

-20 0 20 40 60 80 100

Vaccine Effectiveness (%)
VISION: Absolute VE of COVID-19 bivalent doses received during pregnancy 

against ED/UC encounters among immunocompetent pregnant persons aged 

18-45 years – September 2022 – May 2023*

Adjusted for: Age, ethnicity, race, underlying medical conditions, gestational age at encounter, site, Medicaid status, day of encounter, site facility urbanicity

*Unpublished CDC data

**Doses received during pregnancy for bivalent group

***These interim estimates are imprecise, which might be because of a relatively small number of persons in each level of vaccination or case status. This imprecision 

indicates the actual VE may be substantially different from the point estimate shown, and estimates should therefore be interpreted with caution. Additional data accrual 

should increase precision and allow appropriate interpretation. 53

Vaccine Dosage Pattern Total

tests

SARS-CoV-2-

test-positive,

N (%)

Median 

interval

since last dose,

days (IQR)

Adjusted VE

(95% CI)

Absolute VE

Unvaccinated (ref) 1701 196 (12) -- Ref

Bivalent dose** 191 10 (5) 56 (29, 97) 61 (22, 81)***

0 20 40 60 80 100

Vaccine Effectiveness (%)
▪ Cases infants: hospitalized with COVID-19 as the 

primary reason for admission and with a positive 

SARS-CoV-2 RT-PCR or antigen test result

▪ Control infants: hospitalized with or without 

COVID-19 symptoms and negative SARS-CoV-2 

RT-PCR or antigen test result

– Matched to case-infants by site; hospitalized within 4 

weeks of case-infant admission

▪ Case-control study to assess effectiveness of 

maternal vaccination for COVID-19 in infants < 6 

months of age

▪ 25 pediatric hospitals across 20 states

▪ Infants admitted between March 9, 2022, and 

May 9, 2023

▪ Baseline demographic and clinical characteristics 

obtained via parent interview

▪ Maternal vaccination status verified using state 

vaccination registries, electronic medical records, 

or other sources

Overcoming COVID-19 network

54
Overcoming COVID-19: Effectiveness of maternal vaccination in prevention 

of hospitalization among infants – March 9, 2022 – May 9, 2023

CDC unpublished data. VE estimates adjusted for infant age, sex, race and ethnicity, census region, and month and year of hospitalization. 55

Vaccination during pregnancy* Total Case infants,

N (%)

Median interval 

since last maternal 

dose, days (IQR)

Infant median age at 

hospitalization, days 

(IQR)

Adjusted VE

(95% CI)

Effectiveness of Maternal Vaccination against 

Infant Covid-19 Hospitalization % (95% CI)†

Infants <3 months of age at hospitalization

Unvaccinated (ref) 310 174 (56) NA 44 (27 to 63) Ref

Vaccinated 101 43 (43) 222 (152 to 271) 41 (23 to 66) 56 (24 to 75)*

Infants < 6 months of age at hospitalization

Unvaccinated (ref) 498 281 (56) NA 68 (37 to 125) Ref

Vaccinated 163 78 (48) 236 (190 to 302) 74 (33 to 132) 38 (7 to 59)*

0 20 40 60 80 100

Vaccine Effectiveness (%) 

*Last mRNA or viral vector vaccine dose received between the beginning of pregnancy and 14 days before delivery. 14 people received a bivalent mRNA vaccine.

†These estimates are imprecise, which might be because of a relatively small number of persons in each level of vaccination or case status. This imprecision indicates the actual VE may be 

substantially different from the point estimate shown, and estimates should therefore be interpreted with caution. Additional data accrual should increase precision and allow appropriate 

interpretation.
Bivalent VE in special populations:

people with immunocompromising conditions
VISION: Absolute VE of monovalent and bivalent booster doses against 

hospitalization and critical illness among immunocompromised adults 

aged ≥18 years – September 2022 – May 2023

* These interim estimates are imprecise, which might be because of a relatively small number of persons in each level of vaccination or case status. This imprecision indicates 

the actual VE may be substantially different from the point estimate shown, and estimates should therefore be interpreted with caution. Additional data accrual should increase 

precision and allow appropriate interpretation.

Critical illness defined as admission to intensive care unit or death; case-patients were persons admitted to an ICU or who experienced death associated with COVID-19, and control patients were persons hospitalized

without COVID-19. VE estimates adjusted for age, sex, race and ethnicity, geographic region, and calendar time. Updated from: Link-Gelles et al., MMWR, https://www.cdc.gov/mmwr/volumes/72/wr/mm7221a3.htm 57

mRNA Dosage Pattern

Total

tests

SARS-CoV-2-

test-positive,

N (%)

Median interval

since last dose,

days (IQR)

Adjusted VE

(95% CI)

Hospitalization

Unvaccinated (ref) 3,240 322 (10) -- Ref

Monovalent doses only 11,623 1,169 (10) 359 (242-481) 3 (-12-16)

Bivalent booster, 7-59 days earlier 1,627 144 (9) 33 (19-46) 27 (9-41)

Bivalent booster, 60-119 days earlier 1,862 144 (8) 88 (74-104) 39 (24-51)

Bivalent booster, 120-179 days earlier 1,448 118 (8) 146 (133-161) 11 (-13-31)

Critical illness

Unvaccinated (ref) 3,006 88 (3) -- Ref

Monovalent doses only 10,725 271 (3) 358 (241-481) 16 (-10-35)

Bivalent booster, 7-59 days earlier 1,515 32 (2) 33 (19-46) 41 (8-62)*

Bivalent booster, 60-119 days earlier 1,755 37 (2) 88 (74-104) 43 (13-62)

Bivalent booster, 120-179 days earlier 1,348 18 (1) 146 (133-162) 51 (15-72)*

-20 0 20 40 60 80 100

Vaccine Effectiveness (%)
Summary and conclusions
▪ For estimates of absolute vaccine effectiveness, if unvaccinated are meaningfully 

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

be biased.

– For estimates of relative vaccine effectiveness, residual protection from prior doses is an important 

consideration for interpretation.

▪ Information on prior infection is limited, although we know rates of prior infection in 

the U.S. population are high and vary by age. 

▪ VE against COVID-19-associated hospitalization may underestimate protection against 

more severe COVID-19 disease.

▪ Lack of statistical power to estimate VE for maternal vaccination by timing of doses 

during pregnancy; could not separate monovalent and bivalent doses for protection 

against infant hospitalization

Limitations of VE against severe disease

59
▪ Bivalent boosters are helping provide additional protection against hospitalization, though evidence of waning

▪ For most people who received monovalent doses and are eligible for a bivalent booster, more than a year has 

elapsed since their last monovalent dose. Because of waning, they may have limited remaining protection against 

hospitalization.

▪ Effectiveness against the most critical illness (ICU admission and death) more sustained compared to less severe 

illness

▪ VE during XBB predominance may wane more quickly against hospitalization compared to early variant 

predominant periods

▪ Vaccination during pregnancy provides protection against hospitalization for infants <6 months; protection may be 

highest in the first 3 months

▪ CDC will continue ongoing monitoring of VE, including for all outcomes of interest and for all authorized COVID-19 

vaccines in the U.S. with a focus on assessing new policy recommendations and VE in populations at higher risk of 

severe COVID-19

Conclusions: updates to VE of bivalent COVID-19 boosters

60
CDC COVID-19 Vaccine Effectiveness and 

Policy Team

▪ Amadea Britton

▪ Allison Ciesla

▪ Monica Godfrey

▪ Eric Griggs

▪ Katherine Fleming-Dutra

▪ Dani Moulia

▪ Morgan Najdowski

▪ Erica Okwuazi

VE platforms teams, including:

▪ Sarah Ball

▪ Angela Campbell

▪ Jennifer DeCuir

▪ Monica Dickerson

▪ Margaret Dunne

▪ Kiara Everett

▪ Shikha Garg

▪ Victoria Lazariu

▪ Patrick Mitchell

▪ Palak Patel

And many more!!!

Acknowledgements

61

▪ Caitlin Ray

▪ Sarah Reese

▪ Elizabeth Rowley

▪ Regina Simeone

▪ Zach Smith

▪ Diya Surie

▪ Mark Tenforde

▪ Zack Weber

▪ Laura Zambrano

▪ Sara Oliver

▪ Josephine Mac

▪ Amanda Payne

▪ Lauren Roper

▪ Laura Steinhardt

▪ Evelyn Twentyman

▪ Megan Wallace

▪ Ryan Wiegand
For more information, contact CDC

1-800-CDC-INFO (232-4636)

TTY: 1-888-232-6348 www.cdc.gov

The findings and conclusions in this report are those of the authors and do not necessarily represent the 

official position of the Centers for Disease Control and Prevention.

Questions?