Neutralising antibody levels from COVID vaccines correlate negatively with age

Simon Collins, HIV i-Base

A small US study looking at levels of neutralising antibody levels after a complete Pfizer vaccine schedule correlated negatively with age, with lowest levels in the oldest participants.

The study included 50 people, half women, with median age 50 years and ranging from 21 to 82.

The study reported strength of response against the original US strain and the P.1 variant, which were reduced by approximately 75%.

Although the overall association with age was highly significant, there was also considerable variance in the results (p=0.002; R² = 0.19).

“For the USA-WA1/2020 strain, the youngest participants (20 to 29 years; n = 8) had a geometric mean titre (GMT) of 938 (95% CI: 608 to 1447) and the oldest participants (70 to 82 years; n = 9) had a GMT of 138 (95% CI: 74 to 257), representing an 85% reduction (p<0 .001). For the P1 variant, the youngest participants had a GMT of 165 (95% CI: 78 to 349) and the oldest participants had a GMT of 66 (95% CI: 51 to 86), representing a 60% reduction (p=0.03).”

Importantly, although levels of neutralising antibodies strongly correlate with levels of protection, the relevant threshold for protection has not yet been determined.

Ref: Bates TA et al. Age-dependent neutralization of SARS-CoV-2 and P.1 variant by vaccine immune serum samples.JAMA. doi:10.1001/jama.2021.11656. (21 July 2021).
https://jamanetwork.com/journals/jama/fullarticle/2782428

This article was first posted on 2 August 2921.