05/06/2023
Vaccine efficacy
Pooled estimates of VE after any primary vaccination cycle against symptomatic disease after Omicron infection show a marked waning over time (Figure 1). We found that VE decreased from 52.8% (95% CI, 45.3%-60.3%) at 1 month after completion of any primary cycle to 14.3% (95% CI, 4.4%-24.3%) at 6 months to 8.9% (95% CI, −0.8% to 18.6%) at 9 months. Our estimates suggest that the initial VE could be different depending on the vaccine product, with higher VE found at 1 month from the second dose administration for mRNA-1273 (Moderna) (61.9%; 95% CI, 46.8%-76.9%) and BNT162b2 (Pfizer-BioNTech) (59.3%; 95% CI, 54.3%-64.4%) compared with ChAdOx1 nCoV-19 (AstraZeneca) (45.9%; 95% CI, 38.0%-54.1%) and CoronaVac (Sinovac) (32.4%; 95% CI, 23.7%-36.8%) (eFigure 6 in Supplement 1). We estimated the mean VE to be lower than 5% at 9 months after the administration of the second dose of BNT162b2, mRNA-1273, and ChAdOx1 nCoV-19 and 6 months after the second dose of CoronaVac. Our results suggest that the waning of VE against symptomatic disease after the primary vaccination cycle is remarkably higher for Omicron than for Delta (Figure 2 and eFigure 7 in Supplement 1). Pooled estimates show that VE against symptomatic disease with Delta was 79.6% (95% CI, 72.1%-87.2%) at 1 month after completion of the primary vaccination cycle, 58.5% (95% CI, 48.1%-68.9%) at 6 months, and 49.7% (95% CI, 37.9%-61.5%) at 9 months. This pattern is clearly shown by the estimated half-life of vaccine-induced immunity against symptomatic disease for the 2 variants, decreasing from 316 days (95% CI, 240-470 days) for Delta to 87 days (95% CI, 67-129 days) for Omicron.
This systematic review and meta-analysis of studies reporting vaccine effectiveness at different time points since vaccine administration estimates the waning of protection provided by a variety of COVID-19 vaccine products.
