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This research has not been peer-reviewed. This is a preliminary report that should not be regarded as conclusive, guide clinical practice/health-related behaviour, or be reported in news media as established information.
Background: Age is the major risk factor for mortality after SARS-CoV-2 infection and older people have received priority consideration for COVID-19 vaccination. However vaccine responses are often suboptimal in this age group and few people over the age of 80 years were included in vaccine registration trials.
Methods: We determined the serological and cellular response to spike protein in 100 people aged 80-96 years at 2 weeks after second vaccination with the Pfizer BNT162b2 mRNA vaccine.
Findings: Antibody responses were seen in every donor with high titres in 98%. Spike-specific cellular immune responses were detectable in only 63% and correlated with humoral response. Previous SARS-CoV-2 infection substantially increased antibody responses after one vaccine and antibody and cellular responses remained 28-fold and 3-fold higher respectively after dual vaccination. Post-vaccine sera mediated strong neutralisation of live Victoria (Wuhan-like prototype) infection and although neutralisation titres were reduced 14-fold against the P.1 variant first discovered in Brazil they remained largely effective.
Interpretation: These data demonstrate that the mRNA vaccine platform delivers strong humoral immunity in people up to 96 years of age and retains broad efficacy against the P.1 Variant of Concern.