Each year, vaccination prevents tens of thousands of deaths in the United States and millions of deaths globally. CHR researchers have decades of experience conducting research on vaccine safety and effectiveness.

In recent years, CHR has been at the forefront of research on the COVID-19 vaccine, including contributing data to the Pfizer vaccine clinical trials and to monitoring COVID-19 vaccine safety and effectiveness. In addition, CHR researchers are studying numerous other vaccines, including the newly approved respiratory syncytial virus (RSV) vaccines for pregnant people and older adults.

Many of our vaccine safety studies are conducted through the Vaccine Safety Datalink (VSD), a collaborative project between thirteen healthcare organizations and the Centers for Disease Control and Prevention (CDC). The VSD uses electronic health records data to monitor the safety of vaccines, checking for potential rare adverse events—which can be missed by clinical trials—and monitoring vaccine safety among specific populations, such as pregnant individuals. Distinguished Investigator Allison Naleway, PhD., is the Principal Investigator for the VSD at CHR.

CHR’s Clinical Research and Trials Unit also conducts many research trials examining vaccine safety and effectiveness in the CHR Research Clinic. This includes the original Phase III trial of the Pfizer-BioNTech mRNA-based COVID-19 vaccine (see Featured Study below), as well as COVID-19 booster vaccine trials and clinical trials for vaccines to prevent RSV, pneumococcal disease, Clostridioides difficile infection, influenza, and others.

CHR researchers also study vaccine uptake—the number of people who receive a vaccine—and vaccine coverage—the proportion of an eligible population that has received a vaccine—as well as the epidemiology of vaccine-preventable diseases; attitudes and beliefs about vaccination; and research methods for monitoring vaccine safety. We have also implemented programs within the Kaiser Permanente Northwest health care system designed to increase vaccination rates and improve the vaccination experience.

Featured Studies

Vaccination Uptake and Coverage Among Pregnant Persons in the Vaccine Safety Datalink

Several vaccinations are recommended during pregnancy: those for influenza; COVID-19; tetanus, diphtheria, and pertussis (Tdap); and, most recently, respiratory syncytial virus (RSV). These vaccines offer protection both to the pregnant individual and to their infant. Protection from illness in pregnancy can promote healthy fetal development and prevent preterm labor; protection during infancy can be lifesaving, as newborns are at high risk of serious outcomes of influenza, COVID-19, pertussis, and RSV if they are infected in the first months of life.

Given the large potential benefits of vaccination during pregnancy, is important to monitor the number of pregnant individuals getting recommended vaccines. Real-world data on vaccine uptake and coverage during pregnancy can inform future studies of vaccine safety, and can identify populations that may be at particular risk of infection. We also need to understand the reasons patients give for refusing vaccines during pregnancy, so that concerns can be addressed.

This VSD study provides close to real-time assessments of COVID-19, influenza, and RSV vaccination coverage during the months of the year when infection is highest, and provides end-of-season estimates of vaccination coverage for influenza, COVID-19, RSV, Tdap, and other vaccines given during pregnancy. Live dashboards showing rates of vaccine coverage among pregnant persons are available on the CDC website here for flu, COVID-19, and RSV.


Allison Naleway, PhD
Principal Investigator
Funder: Centers for Disease Control

Phase 3 Clinical Trial of the Pfizer-BioNTech COVID-19 Vaccine vs Placebo

CHR helped conduct the first trial of the innovative mRNA-based vaccine against COVID-19 (BNT162b2) developed by Pfizer and BioNTech, which has since been given to millions of people. The trial began in July 2020 — six months after the COVID-19 virus (SARS-CoV-2) was identified, which was an unprecedented speed. The study enrolled more than 44,000 individuals worldwide, including 98 Kaiser Permanente Northwest members enrolled through CHR. Half of the members received the active vaccine (the first individuals in Portland, Oregon to receive it) and half received the placebo. No one, including the CHR investigators (led by CHR Distinguished Investigator Dr. Stephen Fortmann), was aware of who received the vaccine and who received the placebo.

Thanks in part to the large number of participants, the trial provided clear evidence that the vaccine was safe and effective. It prevented over 90% of infections; further, virtually none of those vaccinated became sick enough to need hospitalization, and none died. The vaccine was approved by the FDA and CDC for use by the public less than six months after the trial started. After the vaccine was found to be effective, KPNW was authorized to “break the blind” and give the placebo group the active vaccine in December 2020.

CHR has continued to be involved in clinical trials for Pfizer COVID-19 booster vaccines.


Stephen Fortmann, MD
Distinguished Investigator
Funder: Pfizer and BioNTech

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