H.F. Sewell / R. M. Agius / D. Kendrick, Covid-19 vaccines: delivering protective immunity, in: BMJ 2020; 371 ([Internet, 2020-12-21](https://doi.org/10.1136/bmj.m4838))
Early in the covid-19 pandemic it was unclear whether and how individuals and populations would develop protective and enduring immunity against SARS-CoV-2, either after infection or vaccination. [...] Early reports indicated that such antibodies decline substantially over less than six months, raising questions about how long protective immunity might last following infection.