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

Whelan M, Galipeau Y, White-Al Habeeb N, Konforte D, Abou El Hassan M, Booth RA, Arnold C, Langlois MA, Pelchat M. Cross-sectional characterization of SARS-CoV-2 antibody levels and decay rates following infection of unvaccinated elderly Individuals. Open Forum Infect Dis. 2023 Jul 20;10(8):ofad384. doi:

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

A CITF-funded study, published in Open Forum Infectious Diseases, reported that individuals 90 years and older had higher levels of infection-acquired SARS-CoV-2 antibodies and more efficient antibody neutralization than younger groups (under 65, and 65-89), but their antibodies decayed at a faster rate. Study samples were collected before vaccine availability. The authors conclude that due to the risk of severe complications from COVID-19, it is important for older individuals to be vaccinated and continue receiving booster vaccinations to maintain immunity against the virus. This study involved collaboration by CITF-funded researcher Dr. Marc-André Langlois with Dr. Martin Pelchat (both from University of Ottawa).

Key findings:

  • Unvaccinated individuals 90 years and older who got SARS-CoV-2 generated high levels of antibodies, correlating with high neutralization efficiency.
  • Although individuals 90 years and older had higher levels of antibodies against the SARS-CoV-2 spike and nucleocapsid protein than those aged 89 and under, their antibodies decayed at a faster rate.
  • In all age groups, antibodies against the SARS-CoV-2 nucleocapsid protein declined fastest over time compared to antibodies against the SARS-CoV-2 spike protein.
  • SARS-CoV-2 IgG antibodies against the receptor-binding domain remained constant over time in individuals 65+.

Understanding how the immune system in older people responds to SARS-CoV-2 is crucial for designing effective vaccination strategies and treatments, especially since older individuals were hit hardest by the virus. For those 90+ who survived COVID-19, the fact that their initial high neutralizing capacity declined with the rapid decay of their antibody levels means that vaccinations are critical in protecting this vulnerable population, whether previously infected or not.

Residual blood samples were collected from individuals in three age groups, under 65 years old, 65-89, and 90 years and older undergoing routine SARS-CoV-2 polymerase chain reaction testing in a community laboratory in Canada between April 28, 2020, and September 21, 2020, prior to vaccine availability.