National Center for Emerging and Zoonotic Infectious Diseases

Vaccine safety updates

Advisory Committee on Immunization Practices (ACIP) meeting

June 23, 2023

Tom T. Shimabukuro, MD, MPH, MBA

Director, Immunization Safety Office

Division of Healthcare Quality Promotion 

Centers for Disease Control and Prevention (CDC)
Session topics

▪ Background on the CDC Immunization Safety Office (ISO) and ISO 

efforts to evaluate studying the safety of the childhood 

immunization schedule (Dr. Tom Shimabukuro)

▪ The childhood immunization schedule and safety: Studies in the 

Vaccine Safety Datalink (Dr. Matthew Daley)

▪ Preliminary evaluation of aluminum content in childhood vaccines 

and risk of asthma in a Danish nationwide cohort (Dr. Anders Hviid)

▪ Discussion

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CDC Immunization Safety Office (ISO) mission

▪ Monitor the safety of vaccines given to children and adults

ISO key activities

▪ Monitor newly recommended vaccines and new recommendations for existing vaccines

▪ Monitor CDC priority vaccines, including seasonal influenza and COVID-19 vaccines

▪ Conduct planned safety studies

▪ Support data needs of the Advisory Committee on Immunization Practices (ACIP)

▪ Assess individual risk factors for adverse events, conduct clinical case reviews, and provide 

clinical consultation to U.S. healthcare providers and health departments about vaccine safety 

questions for individual patients 

▪ Respond to vaccine safety inquiries

▪ Conduct vaccine safety communication and education

▪ Coordinate with state health departments

▪ Prepare for pandemic and emergency responses 3
4

VSD CISA
5

▪ The lack of conclusive evidence linking adverse events to 

multiple immunizations or other “schedule” exposures 

suggests that the recommended schedule is safe.

▪ The risks to participants' health, the cost and time involved, 

and the ethical challenges all make the conduct of an 

[randomized controlled trial] RCT unsuitable for addressing 

the research questions, at least until further work with 

secondary data has been conducted.

▪ Although each new vaccine is evaluated in the context of the 

overall immunization schedule that existed at the time of 

review of that vaccine, elements of the schedule are not 

evaluated once it is adjusted to accommodate a new 

vaccine. Thus, key elements of the entire schedule—the 

number, frequency, timing, order, and age at administration 

of vaccines—have not been systematically examined in 

research studies.

▪ The most feasible approach to studying the safety of the 

childhood immunization schedule is through analyses of 

Institute of Medicine. The Childhood Immunization Schedule and data obtained by [the Vaccine Safety Datalink] VSD.

Safety: Stakeholder Concerns, Scientific Evidence, and Future 

Studies. Washington (DC): National Academies Press (US); 2013.

2013
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Four objectives of White Paper

1. Define types of alternative immunization schedules 

and patterns of undervaccination that could be 

evaluated, focusing on the first 24 months of age

2. Identify plausible adverse event outcomes that could 

be related to the childhood immunization schedule, 

with an emphasis on long-term adverse events

3. Suggest methodological approaches that could be 

used to assess the safety of the recommended 

schedule as a whole

4. Propose next steps for studying the safety of the 

childhood immunization schedule within the VSD

White Paper on Studying the Safety of the Childhood 

Immunization Schedule. For the Vaccine Safety Datalink (cdc.gov)

2014
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.

Photo credit: James Gathany

(https://phil.cdc.gov/Details.

aspx?pid=8876)