A team of scientists from Cambridge University have shed light on the reasons for poor immune responses to the COVID-19 vaccine in older people.
Age is known to be a major risk factor for severe COVID-19, even after vaccination. It is known that older people generally make a poorer immune response to the virus following their primary course of vaccination (usually two doses). This study set out to investigate the response in this group to a booster vaccine dose, as well as to understand the mechanisms underlying any shortcomings in immune response.
The researchers recruited 60 participants with a median age of 67, none of who had previously been infected with SARS-CoV-2. Their findings, published as a preprint (and therefore not yet peer reviewed), showed that people aged 70 or older who had two doses of AstraZeneca then a Pfizer booster produced significantly less effective antibody responses than people under 70.
While the levels of circulating antibodies one month after the booster did not change according to age, the ability of those antibodies to neutralise the virus was impaired in those over 70.
In participants under 70, 4% could not effectively neutralise Delta, compared with 15% of those aged 70 and above. 17% of under 70s could not neutralise Omicron, compared to 22% of those aged 70 and above.
This reduced ability to neutralise SARS-CoV-2 in older participants was found to be due to production of ‘atypical’ B cells expressing certain unexpected proteins.
Importantly, the researchers also observed an impaired T cell response in people over 70.
Overall, the findings demonstrate the extent of impaired vaccine responses in people over 70 after a booster dose, and also shed light on the potential mechanisms underpinning the increased susceptibility to COVID-19 infection in this group.