COVID-19 booster efficiency begins to decline after four months, says CDC study
COVID-19 booster efficiency begins to decline after four months, says CDC study

COVID-19 booster efficiency begins to decline after four months, says CDC study

A study published by the US Centers for Disease Control and Prevention showed that immunity to severe COVID-19 begins to wane four months after receiving a so-called “booster” third dose of the Pfizer or Moderna vaccines.

That first of its kind study drew on data from the VISION Network, a partnership between the CDC and institutions spanning ten states.

Using the exchange of health information and electronic medical record data, the Agency and its partners seek to investigate the longitudinal efficacy of the COVID-19 vaccines approved for use in the United States.

“The MRNA vaccines, including the booster shot, are very effective, but the effectiveness decreases over time,” said study co-author Brian Dixon, director of public health informatics at the Regenstrief Institute and Indiana University Richard M. Fairbanks School of Public Health, in a statement.

“Our results suggest that additional doses may be needed to maintain COVID-19 protection, especially for high-risk populations,” Dixon added.


For this study, researchers analyzed 241,204 emergency rooms and 93,408 admissions in 10 states from August 26, 2021 to January 22, 2022.

An important limitation of the study is that it is designed to estimate the efficacy of the vaccine against COVID-19-associated emergency room visits, emergency room visits, or hospitalizations.

Therefore, study authors noted, the efficacy estimates from the study do not include infections for patients who did not receive medical attention.

Overall, the researchers found that individuals with second and third doses of an mRNA vaccine had greater protection against hospitalizations than against emergency room or emergency visits.

Vaccine efficacy against emergency department or emergency care visits decreased from 97% within the first two months of receiving a booster to 89% efficacy after four months or more during the Delta-dominated period or summer and early fall of 2021.

In the late fall and winter, when the Omicron variant dominated, the vaccine efficacy against emergency room or emergency visits was 87% in the first two months after a third dose and dropped to 66% after four months.

Nevertheless, the protection against serious illness remained quite strong: the effectiveness against Omicron variant-related hospitalization was 91% during the first two months and decreased to 78% after four months.

“Our results confirm the importance of receiving a third dose of mRNA COVID-19 vaccine to prevent moderate to severe COVID-19 disease, especially among those with comorbidity,” said study co-author Dr. Shaun Grannis, vice president of data and analytics at the Regenstrief Institute and professor of family medicine at Indiana University School of Medicine.


The VISION Network relies on data from partner institutions, including Baylor Scott and White Health, Columbia University Irving Medical Center, HealthPartners, Intermountain Healthcare, Kaiser Permanente Northern California, Kaiser Permanente Northwest, Regenstrief Institute and the University of Colorado.

As representatives of the Regenstrief Institute explained, most of the partners are healthcare systems that use a corporate EHR system; Regenstrief uses EHR data from the Indiana Health Information Exchange, which connects several health systems in the state, each with its own EHR system. The institute recently trained an AI model on this data for forecasting individual COVID-19 admission.

Each institution can use the data it contributes to the VISION network to address localized research issues, representatives said. Members of the network also suggest ideas for surveys.

Previous studies have included those that show vaccine efficacy in comparison with previous COVID-19 infectionse.g.

“While the CDC provides significant and important leadership of the network, member institutions are heavily involved in proposing research questions, study design, and interpretation of analyzed data,” Regenstrief representatives said.

“We are also actively involved in data management and data quality assurance, as we extract information from EHR systems for submission to the network.”


“The protection afforded by mRNA vaccines declined in the months following a third dose of vaccine, supporting further booster dose considerations to maintain protection against moderate to severe COVID-19 disease,” Regenstriefs Grannis said in a statement.

Kat Jercich is senior editor of Healthcare IT News.
Twitter: @kjercich
Email: [email protected]
Healthcare IT News is a HIMSS Media publication.

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