This is a summary, written by members of the CITF Secretariat, of:

Zhang A, Breznik JA, Clare R, Nazy I, Miller MS, Bowdish DME, Costa AP. Antibody Responses to Third-Dose mRNA Vaccines in Nursing Home and Assisted Living Residents. J Am Med Dir Assoc. 2022 Jan 15:S1525-8610(21)01109-9. doi: 10.1016/j.jamda.2021.12.035

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

In this study, led by CITF-funded researchers Drs. Andrew Costa and Dawn Bowdish at McMaster University and published in JAMDA, people in retirement and nursing homes were sampled to measure antibody mediated immunity after the second and third doses of mRNA SARS-CoV-2 vaccines. Researchers found that the third vaccine dose brought about levels of antibodies that neutralize COVID-19Neutralizing antibodies are the antibodies capable of inactivating the target (SARS-CoV-2, in this case) by binding strongly to the spike protein and stopping/inhibiting further infection were much higher than what was achieved post-second dose. People in retirement homes were found to have equal similar levels of neutralizing antibodies compared to nursing home residents.

Key findings include:

  • Higher neutralization capacity was achieved after a third booster dose, compared to the second dose.
  • Residents of both retirement and nursing homes had neutralization capacity against the Beta variant following the third dose, whereas 20.8% had no detectable neutralization capacity after the second dose.
  • Beta variant neutralization was lower compared to the capacity to neutralize the wild type variant.
  • There were no differences in median neutralization titers between nursing home residents and retirement home residents 12 to 77 days post 3rd

This study was carried out in both nursing homes and retirement homes – the residents in the former are generally frailer and in need of more care than in the latter. For assessment of immunity after the second dose, a total of 418 nursing home residents were recruited, with an average age of 82 years and 63.5% were women. There was a similar distribution between vaccine series of Moderna-Moderna (52.9%) and  Pfizer-Pfizer (46.4%). For assessment of the third dose, a total of 103 nursing home residents were recruited 12-77 days post third dose, together with 95 retirement home residents recruited 12-77 days post third dose. Both groups had an average age above 80 years and were mostly women (63% and 65%). Nursing home residents received Moderna-Moderna-Moderna (66.0%), Pfizer-Pfizer-Moderna (17.5%), and Pfizer-Pfizer-Pfizer (16.5%); whereas assisted living residents received Pfizer-Pfizer-Pfizer (61.1%), Moderna-Moderna-Moderna (22.1%), Pfizer-Pfizer-Moderna (14.7%), and Moderna-Moderna-Pfizer (2.1%).

Overall, these findings support the need for third vaccine doses in people living in nursing homes or retirement homes. As we do not have information regarding neutralization capacity to Omicron in this population yet, continued monitoring is needed to assess how efficient and durable immunity will be.