Findings from a CITF-funded study led by Drs. Andrew Costa and Dawn Bowdish at McMaster University helped inform the federal government’s decision to recommend a third dose of COVID-19 vaccine for long-term care residents. More than 97% of residents produced an initial antibody response to vaccination that is likely to provide protection against the virus. However, three to five months following the second dose, researchers found a drop in the antibody level in about 20% of residents, to the point where their antibody response may not be strong enough to provide effective protection. Their research is published in The Journal of the American Medical Directors Association.

While acknowledging that waning antibody levels are not the only measure of vulnerability to COVID-19, the researchers concluded that the antibody wane among long-term care residents was so significant compared to younger, healthier Canadians that a third dose is certainly a prudent approach to avoid more deaths and sickness. About 70% of Canada’s COVID-19 deaths have occurred in long-term care homes.

Researchers looked at immune responses to Moderna’s SpikeVax and Pfizer-BioNTech’s Cominarty vaccines. While both elicited good antibody levels, most residents had a stronger response to the former, which contains a higher amount of mRNA. Therefore, they recommend using the SpikeVax vaccine for third doses and for older and frailer people moving forward. With its higher amount of active ingredient, SpikeVax might help give the aging immune system an added boost.

The study, which was conducted in partnership with Schlegel Villages, St. Joseph’s Health System, and Health Sciences North Research Institute was based on blood samples taken from 138 residents in eight long-term care homes throughout Ontario between March and July 2021.

Read more in our news release

Breznik JA, Zhang A, Huynh A, Miller MS, Nazy I, Bowdish DME, Costa AP, Antibody Responses 3-5 Months Post-Vaccination with mRNA-1273 or BNT163b2 in Nursing Home Residents, JAMDA, DOI: https://doi.org/10.1016/j.jamda.2021.10.001