David H. Canaday

COVID-19: Immunity Drops Significantly Six Months After Pfizer Vaccine in Both Nursing Home Residents and Health Care Workers

MedicalResearch.com Interview with:

David H. Canaday

Dr. Canaday

David H. Canaday, MD
Associate Director of Research
Geriatric Research, Education and Clinical Center (GRECC),  Cleveland VA
Professor, Division of Infectious Disease,
Case Western Reserve University
Cleveland, Ohio

MedicalResearch.com: What is the background for this study?

Response: We were interested in following up on a prior study where we determined that nursing home residents, and in particular those that were given the Pfizer shot who never had COVID-19 in the past, had 4 fold less antibodies against the key Spike protein of the coronavirus than did the group of health care workers who were the other group studied.

We wanted to see how those antibodies levels in these groups held up over 6 months. 

MedicalResearch.com: What are the main findings?

Response: We restudied the same subjects 6 months later and found that the anti-spike antibodies levels drop about 10 fold over those 6 months. There was a fairly similar drop in both nursing home residents and health care workers. Also there was a similar drop in those that had COVID-19 before the shot and were then vaccinated. Those persons including both nursing home residents and health care workers that had COVID-19 prior to vaccination had the highest levels of anti-spike antibodies at 2 weeks and 6 months post vaccine. On the other hand, those nursing home residents who had never had COVID-19 before they were vaccinated had very poor ability to neutralize infection in 70% of them.

MedicalResearch.com: What should readers take away from your report?

Response: Even though the antibodies drop up to 10 folds on average all subjects in the study still had some level of anti-coronavirus antibodies present. So there is some immunity present more than prior to any vaccine. There are data emerging in other labs that having more antibodies does go along with better protection. Our data are part of the evidence that CDC and other policy leaders will use to shape booster policy decisions.

MedicalResearch.com: What recommendations do you have for future research as a result of this work?

Response: We are actively studying the other components of the immune system namely the T cells to see how they develop and change over time against the coronavirus. Also we and others need to work to find an immune correlate which is some type of blood test that can predict when someone is protected. This would make a clear pathway to decide when individual people need to be boosted and assist in developing even more optimal vaccines for protection from COVID-19 in the future.

Disclosures: Potential conflicts of interest. Dr. Canaday is recipient of investigator-initiated grants to his universities from Pfizer to study pneumococcal vaccines and Sanofi Pasteur and Seqirus to study influenza vaccines. He has done consulting work for Seqirus. Dr. Canaday’s university has not deemed any of these as a significant conflict of interest.


Significant reduction in humoral immunity among healthcare workers and nursing home residents 6 months after COVID-19 BNT162b2 mRNA vaccination
David H. Canaday, Oladayo A. Oyebanji, Debbie Keresztesy, Michael Payne, Dennis Wilk, Lenore Carias, Htin Aung, Kerri St. Denis, Evan C. Lam, Christopher F. Rowley, Sarah D. Berry, Cheryl M. Cameron, Mark J. Cameron, Brigid Wilson, Alejandro B. Balazs, Christopher L. King, Stefan Gravenstein
medRxiv 2021.08.15.21262067; doi: https://doi.org/10.1101/2021.08.15.21262067Pf

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Last Updated on September 2, 2021 by Marie Benz MD FAAD