Providence researchers assess changes in COVID-19 vaccine effectiveness over time

Past research has suggested the protection offered by COVID-19 vaccines may wane over time, prompting consideration of booster vaccinations. To better understand and respond to this phenomenon, a team of researchers from the Providence Research Network analyzed Providence hospital data to assess vaccine effectiveness against hospitalization for severe COVID-19 over time, as well as determine which patients are most vulnerable to waning protection.

Their study, published in March 2022 in the journal The Lancet Respiratory Medicine, highlights how different vaccines decline in protection over time after they are administered, especially for patients over 75 and those with compromised immune responses. Findings confirmed the overall effectiveness of vaccines in preventing severe infection resulting in hospitalization from COVID-19. However, they also indicated a decline in protection after six months. 

The researchers, including Providence’s Bill Wright, PhD, George Diaz, MD, and Ari Robicsek, MD, examined data from nearly 50,000 hospital admissions between April and November of 2021. The data showed that vaccines were 94 percent effective at preventing hospitalization 50-100 days after receiving the shot. However, that fell to 80.4 percent 200-250 days later, with more rapid declines after 250 days.

The study also identified factors associated with reduced vaccine effectiveness, including advanced age (80+), comorbidities such as cancer, transplants, chronic kidney disease, hypertension, or heart failure, the amount of time that had elapsed since being vaccinated, and the type of vaccine one received.

When looking at the effectiveness of the Moderna, Pfizer, and Janssen COVID vaccines over time, the team found that the Moderna vaccine offered the best overall protection. The Pfizer-BioNTech vaccine offered initial protection equivalent to Moderna’s, but that protection declined more rapidly. Those who received the Janssen vaccine also had higher odds of experiencing a severe breakthrough infection compared to Moderna.

“This data helps us understand differences in waning protection by vaccine type and identify the key risk factors for severe breakthrough infections to help inform the targeting of potential vaccine booster programs,” said Amy Compton-Phillips, M.D., president, clinical operations at Providence. “Unlike most other studies, our data stretched beyond six months, where we found evidence of rapidly waning protection, especially for patients 80 or older. We were also able to identify important differences by vaccine type and patient characteristics that should help inform potential booster programs.”

Researchers at Providence have been on the front line of understanding and treating COVID-19 since the early days of the pandemic when we treated the first U.S. case in January 2020. The data infrastructure that was used to complete the study is still being used to monitor vaccine effectiveness across the Providence footprint in the face of evolving COVID-19 variants.

Read the full paper in The Lancet 

Learn more about the Providence Research Network at our website