COVID-19 Vaccine Safety Technical (VaST) 

Work Group 

Assessment

Grace M. Lee, MD MPH

Advisory Committee on Immunization Practices

April 23, 2021
Dynamic decision-making process

ACIP VaST Work 

Group

ACIP COVID 

Vaccines Work 

Group

ACIP

Risk assessment Benefit-risk 

assessment

Recommendations 

for use
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

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VaST Activities

Pre-authorization

Jun-Dec 2020

• 14 meetings to 

prepare for vaccine 

safety surveillance 

in the U.S.

ACIP Recommendations

• Dec 12 –

Pfizer/BioNTech

• Dec 14 – 1st dose 

administered in 

U.S.

• Dec 19 – Moderna

• Feb 28 – Janssen

Post-authorization

Dec 21-present

• 17 independent 

meetings to review 

vaccine safety data 

across multiple 

surveillance 

systems
VaST Meeting - April 12

CVST with thrombocytopenia

 6 cases of CVST with thrombocytopenia identified as a rare, 

but serious adverse event following Janssen vaccine

 Risk factors for CVST with thrombocytopenia not well 

understood

 Timely and transparent communication with healthcare 

providers and the public is crucial to maintain confidence in 

the vaccination program

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HAN Communication – April 13
ACIP Meeting – April 14

CVST with thrombocytopenia

 Review of reported cases of CVST with thrombocytopenia 

after COVID-19 vaccines 

 Discussion about the need for additional information to 

support evidence-based decision making, including

–

–

Age and gender-specific risk estimates

Evaluation of the benefit-risk balance of using Janssen 

vaccine in specific subgroups

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VaST Meeting - April 19

Thrombosis with Thrombocytopenia Syndrome 

 Review of new Brighton Collaboration definition of Thrombosis with 

Thrombocytopenia Syndrome (TTS)

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–

–

Will facilitate investigation across surveillance systems

 Health Network Alert (HAN) supported enhanced case finding

Age and gender-specific rates of TTS following Janssen vaccine 

requested for risk assessment

 Review of data from VSD RCA and VA RCA

No safety signal identified for CVST, other thromboembolic disease, or 

thrombocytopenia identified following Janssen vaccine (>200,000 

doses)

 Update from Global Advisory Committee on Vaccine Safety (GACVS) on 

TTS cases following AstraZeneca vaccine

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VaST and CVWG Meeting - April 22

 Risk for TTS following Janssen vaccine

–

–

–

–

7 per million doses in females <50 years* (highest in 30-39 years)

<1 per million doses in female 50+ and males* 

 Other potential risk factors 

Obesity (BMI>30), OCP use, hypothyroidism, hypertension

 Outcomes 

3 deaths, 7 remain hospitalized (4 in ICU), 5 discharged home

 Benefit-risk assessment and Evidence-to-Recommendation framework 

discussed

*Includes all doses (not adjusted for follow-up time) 9
VaST Summary

 Risk of TTS appears to be highest in female <50 years

–

–

–

–

Other risk factors for TTS not well established yet

 Risk mitigation strategies 

Minimize exposure in high-risk populations 

Increase awareness & ensure timely diagnosis and management of TTS

Educate patients about benefits and risks of available vaccines

 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

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

Susan Hiers

Jared Woo

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