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

Breznik JA, Huynh A, Zhang A, Bilaver L, Bhakta H, Stacey HD, Ang JC, Bramson JL, Nazy I, Miller MS, Denburg J, Costa AP, Bowdish DME, other members of the COVID-in-LTC Investigator Group. Cytomegalovirus Seropositivity in Older Adults Changes the T Cell Repertoire but Does Not Prevent Antibody or Cellular Responses to SARS-CoV-2 Vaccination. Journal of Immunology, September 28, 2022, ji2200369; DOI:

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

Data presented in a CITF-funded study by Drs. Dawn Bowdish and Andrew Costa (both from McMaster University), along with other members of the COVID-in LTC Investigator Group, showed that people aged 65+ who were seropositive with cytomegalovirus (CMV) did not have a higher incidence of COVID-19. CMV seropositivity in older adults did not have a negative impact on the longevity of vaccine-elicited antibodies and neutralization, or T cell memory recall responses. This, even several months after second or third doses of COVID-19 vaccines. Yet, there were subtle changes in antibody and cellular responses in CMV-seropositive individuals between vaccine doses and in individuals with prior COVID-19. The article was published in the Journal of Immunology.

This study is important because CMV:

  • is a common and persistent beta-herpes virus found in ∼60-90% of adults worldwide, and
  • seropositivity increases with age and is implicated as a significant contributor to age-associated immune dysfunction.

It has been suggested that CMV reactivation in those 65+ contributes to more severe COVID-19.  CMV seropositivity has been associated with impaired antibody production by specialised white blood cells called B-cells and cellular memory recallUpon exposure to SARS-CoV-2 to which the individual has been previously exposed, memory B and T lymphocytes quickly proliferate and differentiate into effector cells. responses.

Key Findings:

  • 4% of participants (129 of 186), with a median age of 85, were found to be CMV positive.
  • CMV serostatus did not affect anti-spike and anti-receptor binding domain IgG Ab levels, nor neutralization capacity against the original (wild type) or Beta variant of SARS-CoV-2 several months after an mRNA vaccination.
  • CMV positivity did not alter the ability of older adults to generate lasting CD4 or CD8 T cell memory. It also did not affect the incidence of T cell memory recall activation in response to the SARS-CoV-2 spike protein several months after second and third dose vaccinations.

The study cohort of participants in the COVID in Long-Term Care Study (65 years of age and older) were recruited from assisted living facilities (17 nursing homes and 8 retirement homes) in Ontario between March and December 2021. Participants received two doses of Moderna Spikevax or Pfizer Comirnaty mRNA vaccines, and a third mRNA vaccine dose in fall 2021 at least six months from the last dose. It did not exclude individuals with particular health conditions or prescribed medications.