Adults who are severely immunosuppressed, such as those who have had solid organ transplants, may not respond as well to COVID-19 vaccines and are at much higher risk of severe disease [footnote 7]. JCVI advises that those adults who are severely immunosuppressed should be offered COVID-19 booster revaccination at the start of the booster programme. Unless otherwise eligible, adult household contacts of immunosuppressed individuals should be offered booster revaccination alongside those in stage 2 with allowance for operational flexibility.
AstraZeneca data on the durability of protection and immune responses following COVID-19 vaccination [unpublished]. 
Pfizer-BioNTech data on the durability of protection and immune responses following COVID-19 vaccination [unpublished]. 
Moderna data on the durability of protection and immune responses following COVID-19 vaccination [unpublished]. 
Dan, Mateus, Kato, et al. Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection. Science. 2021 Feb 5; 371(6529). 
Modelling on influenza activity in the 2021/22 season. University of Warwick [unpublished]. 
National Immunisation Schedule Evaluation Consortium (NISEC) data [unpublished]. 
Monin-Aldama, Laing, Muñoz-Ruiz et al. Interim results of the safety and immune-efficacy of 1 versus 2 doses of COVID-19 vaccine BNT162b2 for cancer patients in the context of the UK vaccine priority guidelines. MedRxiv.