COVID-19 Vaccine Safety Technical (VaST) 

Work Group 

Assessment

Grace M. Lee, MD MPH

VaST ACIP Chair

Advisory Committee on Immunization Practices

May 12, 2021
COVID-19 Vaccine Safety Technical (VaST) Work Group

Objectives

 Review, evaluate, and interpret post-authorization/approval 

COVID-19 vaccine safety data

 Serve as the central hub for technical subject matter expertise 

from federal agencies conducting post-authorization/approval 

safety monitoring

 Advise on analyses, interpretation, and data presentation

 Provide updates to the ACIP COVID-19 Vaccines Work Group and 

the ACIP on COVID-19 vaccine safety

2
U.S. Vaccination Program

 As of May 10

–

–

262 million doses 

administered in the U.S.

• 140 million PfizerBioNTech

• 113 million 

Moderna

• 9 million Janssen

153 million individuals 

who received ≥1 dose
start 

of 

vax

active surveillance, passive 

surveillance, case consults

Vaccine Safety Monitoring Timeline
VaST Activities

Dec Jan Feb Mar Apr May

Dec 12 

Pfizer/ 

BioNTech 

(16+)

Feb 28 

Janssen 

(18+)

Apr 13 

Janssen 

safety 

pause

Dec 19 

Moderna 

(18+)

Apr 23 

Janssen 

resumed 

with 

warning 

about TTS

Dec 21, 2020 – present: •

•

20 independent meetings to review vaccine safety data

4 joint meetings with COVID-19 Vaccines Work Group focused on 

safety
Janssen Vaccine - Thrombosis with Thrombocytopenia 

Syndrome (TTS)

VaST meeting

April 12

• CVST with 

thrombocytopenia 

identified as a rare, 

but serious adverse 

event following 

Janssen vaccine

CDC and FDA 

April 13

• Safety pause of 

Janssen COVID-19 

vaccine

• HAN issued to 

ensure timely 

recognition and 

appropriate 

management

ACIP meeting 

April 14

• Review of TTS 

cases

• Request for 

additional 

information to 

support evidencebased decision 

making
 April 12

 April 19

 April 22

April 23: ACIP Meeting

 April 26

 May 3

 May 10

7

VaST Meetings to Review Data on 

Thrombosis with Thrombocytopenia Syndrome (TTS)
TTS – reviewed at VaST Meetings*

 Enhanced monitoring and refined CDC case ascertainment 

approach used for TTS cases following Janssen in VAERS

–

–

–

–

Median age 40 years (range 18-59) 

28 cases identified - 22 female, 6 male

 Review of data from VSD RCA and VA RCA

Broad electronic algorithms implemented to capture potential 

CVST or TTS events, followed by rapid review of electronic 

medical records for confirmation

No safety signals identified for CVST or TTS following mRNA or 

Janssen vaccines

Most recently, May 10; data through May 7 8
9
10
VaST Summary

 No confirmed TTS cases following mRNA vaccines

 Risk of TTS following Janssen vaccine highest in females <50 years

 Continue risk mitigation strategies 

–

–

Educate patients about benefits and risks of available vaccines

Earlier recognition and timely management of TTS

 VaST will continue to monitor TTS, thromboembolic disease, and 

thrombocytopenia in all available vaccine safety surveillance 

systems

 VaST will update the ACIP COVID-19 vaccines workgroup, ACIP 

secretariat and ACIP on a regular basis 

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VaST Members

VaST Members

Grace Lee (ACIP)

Robert Hopkins (NVAC)

Matt Daley

Veronica McNally

Keipp Talbot

Kathy Edwards

Lisa Jackson

Jennifer Nelson

Laura Riley

Robert Schechter

Patricia Whitley-Williams

CDC Co-Leads

Lauri Markowitz

Melinda Wharton

Ex Officio and Liaison Representatives 

Tatiana Beresnev (NIH)

Karen Farizo; Hui Lee Wong (FDA)

Judith Steinberg (OIDP)

Jeffrey Kelman (CMS)

Matthew Clark (IHS)

Mary Rubin (HRSA)

Fran Cunningham (VA)

Limone Collins (DoD)

Administrative Support

Jared Woo

12 12
For more information: www.cdc.gov/COVID19

TTS Updates: 

Work Group Interpretation 

Sara Oliver MD, MSPH

ACIP Meeting

May 12, 2021
14 https://www.cdc.gov/mmwr/volumes/70/wr/mm7017e4.htm?s_cid=mm7017e4_w

https://www.cdc.gov/vaccines/covid-19/downloads/talking-patients-Janssen-COVID-19-Vaccine-safety.pdf

“ACIP reaffirmed its interim recommendations for use of 

the Janssen COVID-19 vaccine in all persons aged ≥18 

years under FDA’s EUA, which now includes a warning

that rare clotting events might occur after vaccination, 

primarily among women aged 18-49 years. 

Patient and provider education about the risk for TTS 

with the Janssen COVID-19 vaccine, especially among 

women aged <50 years, as well as the availability of 

alternative COVID-19 vaccines, is required to guide 

vaccine decision making and ensure early recognition 

and clinical management of TTS.”
Janssen COVID-19 vaccine administration: 

Before and after the safety pause

15

 1,209,404 doses of the Janssen COVID-19 vaccine administered after the safety 

pause

0

50

100

150

200

250

300

350

18-49 years ≥50 years

Thousands

Females Males

After the Safety Pause*

(April 13–May 11, 2021)

Before the Safety Pause*

(Before April 13, 2021)

0

0.5

1

1.5

2

18-49 years ≥50 years

Females Males

Millions

*Does not include administration records from Texas, or records without a valid age or sex 

CDC | Data as of: May 11, 2021 6:00am ET
 The Risk/benefit analysis was updated with the updated incidence of TTS and 

reviewed by the COVID-19 vaccines Work Group

 The Work Group’s interpretation is that the benefits still outweighed the risks

at this time, and no updates to vaccine policy are needed at this time

 The Work Group will continue to review TTS updates and the Risk/benefit analysis

 If/when the Work Group’s assessment is that updates to recommendations for 

use of the Janssen COVID-19 vaccine should be considered, the Risk/benefit 

analysis will be presented to ACIP again, along with updated policy 

considerations

Janssen COVID-19 vaccine: 

Risk/benefit analysis 

16
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.

Thank you!
Janssen COVID-19 vaccine administration: 

Before and after the safety pause

18

Pre Pause 

(Before April 13, 2021)

Post Pause

(April 23, 2021 - May 11, 2021)

Female Male Female Male

n % n % n % n %

18-29 years old 488,795 15% 464,502 14% 50,420 17% 112,525 21%

30-39 years old 521,914 16% 476,125 14% 46,497 15% 97,630 18%

40-49 years old 558,793 17% 554,773 17% 52,723 17% 98,091 18%

50-64 years old 1,155,482 35% 1,153,702 35% 97,652 32% 163,970 30%

64+ years old 547,140 17% 653,789 20% 57,998 19% 68,255 13%

Total 3,272,124 3,302,891 305,290 540,471