BC-CfE studies immune response to COVID-19 vaccines among the elderly

posted on September 21, 2021

A new research report by the BC-CfE adds to the growing body of evidence that elderly individuals don’t mount as strong, or durable, immune responses to the COVID-19 vaccines as compared to younger individuals. This COVID-19 Immunity Task Force (CITF)-funded study was done in collaboration with Providence Health Care and Simon Fraser University.

Titled “Reduced magnitude and durability of humoral immune responses by COVID-19 mRNA vaccines among older adults”, the research was comprised of data from 151 individuals. These individuals were: 89 healthcare workers, 23 residents of long-term care and tenants of assisted-living, and 39 seniors living in the community.

We know mRNA vaccines reduce COVID-19 incidence and severity. However, the durability of vaccine-induced immune responses, particularly among the elderly, remains incompletely characterized.

The study analyzed three different kinds of antibody immune responses up to three months following the second dose of a COVID-19 vaccine. First the researchers measured the total amount of antibodies against the viral spike protein that were produced by the vaccine. Second, the researchers looked at the ability of these antibodies to block the interaction between the viral Spike protein and its cellular receptor ACE2, which is the cell surface protein that allows the coronavirus to infect human cells. Finally, the researchers measured the ability of vaccine-induced antibodies to block the SARS-CoV-2 virus from infecting cells in vitro.

The researchers found that after both one and two vaccine doses, older adults exhibited lower antibody responses for all three measures tested. Importantly, the association between older age and poorer vaccine responses differences remained even after adjusting for sociodemographic factors, other underlying health conditions, and vaccine-related variables.

In addition, the researchers found that vaccine-induced immune responses had waned substantially in everyone, regardless of age, by three months after the second dose. which means that the immune responses of older adults remained weaker at all time points tested. The researchers also found that older adults also displayed reduced ability to block ACE2 binding by the Delta variant, which is now circulating widely.

The research adds to a growing body of evidence that the antibody immune response to COVID-19 mRNA vaccines is significantly weaker with age, and universally wanes over time. This will likely reduce antibody-mediated protection against SARS-CoV-2 and the Delta variant as the pandemic progresses. In the pre-print version of the study, the researchers said, “We conclude that older adults may benefit from additional immunizations or boosters, as a priority.”

Because the peak vaccine-induced immune responses of older adults were less robust than those of younger adults to begin with, and because we are now seeing a decline in these responses over time, older adults may begin to become susceptible to SARS-CoV-2 sooner, as the vaccine effects wear off.
- Dr. Zabrina Brumme, BC-CfE Laboratory Director and senior author for this study.

This kind of research helps public health officials and researchers in Canada better understand immunity from current COVID-19 vaccines. The findings were presented to the National Advisory Committee on Immunizations at their recent September meeting. They have also been shared with public health officials in BC.

This work was supported by the Public Health Agency of Canada through a COVID-19 Immunology Task Force COVID-19 "Hot Spots" Award, the Canada Foundation for Innovation through Exceptional Opportunities Fund COVID-19 awards, and the National Institute of Allergy and Infectious Diseases of the National Institutes of Health.

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Story updated on December 9th, 2021

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BC-CfE studies immune response to COVID-19 vaccines among the elderly

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