The impact of expanded adolescent vaccination against COVID-19 depends on the epidemic status: a mathematical modelling study

The study evaluated the impact of adolescent COVID-19 vaccination in England at two different epidemic periods using the Covasim mathematical model. During August to November 2021, amid a large Omicron BA.1 epidemic wave, expanded vaccination of adolescents aged 12 and older prevented approximately 3 million cases and approximately 1.01 million SARS-CoV-2 infections in the 2-6 months following vaccination onset. Conversely, during August to November 2022, when the Omicron epidemic was in an endemic stage, additional adolescent vaccination did not significantly reduce COVID-19 burden in the entire population or within the vaccinated cohort. Researchers concluded that the effectiveness of adolescent vaccination depends on timing and speed of implementation, other concurrent interventions, and the epidemic status at the time of vaccination.