15 August 2018 - - A Kaiser Permanente study of more than 80,000 children born over a 4-year period showed that the prenatal Tdap vaccination (tetanus, diphtheria, acellular pertussis) was not associated with increased risk of autism spectrum disorder in children, the California-based HMO said.

The study was published in Pediatrics.

The Advisory Committee on Immunization Practices, which provides guidance on the use of vaccines for the United States, recommends pregnant women receive the Tdap vaccine to prevent pertussis infection, but some women still hesitate.

Kaiser Permanente said its researchers were able to comprehensively study the hypothesized link between Tdap and autism because of the organization's large and diverse patient population.

In Southern California, Kaiser Permanente provides health care in 15 hospitals and about 220 medical offices to approximately 4.4m members who are broadly representative of the area's population. Recommended vaccinations are free to all members.

This retrospective cohort study looked at the autism diagnosis for children born at Kaiser Permanente hospitals in Southern California between Jan. 1, 2011 and Dec. 31, 2014.

The study included 81,993 children and found that:

Prenatal Tdap vaccination coverage ranged from 26 % for the 2012 birth cohort to 79 % for the 2014 birth cohort.

The autism spectrum disorder incidence rate in children was 1.5 % in the maternal Tdap vaccinated group and 1.8 % in the maternal unvaccinated group, comparable to autism rates in the United States (1.7 %).

Analyses of the data extracted from electronic health records showed that Tdap vaccination during pregnancy was not associated with increased autism spectrum disorder risk in children.

Results were consistent across study birth years and among first-born children.

Other authors on this study include Darios Getahun, MD, PhD, Vicki Chiu, MS, and Lina Sy, MPH, all of the Kaiser Permanente Southern California Department of Research and Evaluation.
This study was supported by Kaiser Permanente Southern California internal research funds.


The Department of Research and Evaluation conducts high-quality, innovative research into disease etiology, prevention, treatment and care delivery. Investigators conduct epidemiologic research, health services research, biostatistics research, and behavioral research as well as clinical trials.

Major areas of study include chronic disease, infectious disease, cancer, drug safety and effectiveness, and maternal and child health.

Headquartered in Pasadena, California, the department focuses on translating research to practice quickly to benefit the health and lives of Kaiser Permanente Southern California members and the general public.

Founded in 1945, Kaiser Permanente currently serves more than 12.2m members in eight states and the District of Columbia.

Care for members and patients is focused on their total health and guided by their personal Permanente Medical Group physicians, specialists and team of caregivers.