Antibody Responses to SARS-CoV-2 Vaccine in Nursing Home Residents Support a Bi-Annual Update Schedule

Background: The COVID-19 pandemic has greatly affected nursing home residents (NHRs), a vulnerable group with high rates of illness and death. While vaccination is essential for reducing infections and severe outcomes in the short term, it is important to understand how long antibody levels and neutralizing activity last. This understanding will help us create effective public health strategies for the long term. According to current CDC guidelines, individuals over the age of 65 should receive a booster dose six months after their previous vaccination. Methods: This observational retrospective cohort study analyzed post-vaccination serum from samples with up to 400 days of follow-up from 697 NHRs and 127 healthcare workers (HCWs) across Northeast Ohio and Rhode Island. Analyses were conducted to model decay rates of both neutralizing and binding antibody titers and the impact of previous exposures to SARS-CoV-2 on these decay rates. Results: Results indicate that NHRs show Wuhan and Omicron BA.4/5 neutralizing and binding antibody titers diminish significantly from 2 weeks to 12 months post-vaccination. NHRs with prior infection show higher peak antibody titers and slower decay than those naive to infection. Antibody levels after vaccination for infection-naive NHR residents lagged HCW and NHR with prior infection, but then decayed at a similar rate. Conclusion: The immunologic findings in this cohort of NHR are in line with the existing real-world clinical effectiveness data in older individuals and support the CDC recommendation of a bi-annual vaccination to reduce severe COVID-19 outcomes in persons age 65 and older.