Prediction of Covid-19 vaccine effectiveness in adult populations and in clinically-vulnerable subgroups

Predictions of Covid vaccine effectiveness could support rapid and effective measures against the pandemic. Our modelling boosts the accuracy and applications of these predictions, especially to subgroups. We model the symptomatic effectiveness of Comirnaty or Vaxzevria with 50% neutralising antibody titres from a large UK immunogenicity study and with up to 68 effectiveness estimates from 23 vaccine studies. We predicted effectiveness in adult populations, age and disease subgroups, with 45% (95% CI: 27–63) predicted against Omicron BA.1 for Comirnaty boosters in haemodialysis patients. Prediction errors for two Comirnaty doses in adults were 1.9%, 2.6% and 0.4%, against the Alpha, Beta and Delta variants, versus 3.6%, 28% and 8.7% with a state-of-the-art alternative; and for Vaxzevria, 1.1% and 0.7% against Alpha and Delta, versus 18% and 20.4%. Identical titres implied between 18% (95% CI: 1–33) and 31% (95% CI: 13–50) lower Comirnaty effectiveness against Omicron BA.1 than Delta.