Guidance on COVID-19 vaccination published by the government sets out advice for healthcare professionals on the first two vaccines expected to become available in the UK - the Pfizer/BioNTech and Oxford/Astra Zeneca products - along with updates on how the vaccines should be administered and priority groups for vaccination.
The government has also published recommendations and resources on training staff expected to take part in the vaccination campaign - which could start from as soon as 7 December.
The advice says there is 'no evidence on the interchangeability of the different COVID-19 vaccines' likely to become available in the UK - and that 'every effort should be made' to complete vaccination of individuals with two doses of the same vaccine.
However, in cases where the same vaccine is not available, or where the type of first dose received is unknown, the guidance says it is 'reasonable to offer a single dose of the locally available product' - and that this is the 'preferred option' where individuals are at 'immediate high risk or considered unlikely to attend again'.
Although the Pfizer/BioNTech and Oxford/Astra Zeneca vaccines are different, the guidance suggests that because both are based on the SARS-CoV-2 spike protein, a second dose of either vaccine is likely to boost patients' response to the first dose - and that follow up with a further dose would be unnecessary.
Although available data 'do not indicate any safety concern or harm to pregnancy, there is insufficient evidence to recommend routine use of COVID-19 vaccines during pregnancy', the guidance confirms.
It recommends that vaccination should be 'postponed until completion of pregnancy' - with pregnant women in at-risk groups, including healthcare workers, offered vaccination 'as soon as possible after completion of pregnancy'.
Vaccine trials in children have only just begun and there are currently 'very limited data on safety and immunogenicity in this group', the guidance adds. Given low risk of severe illness for children and young people and the lack of data on vaccine safety, 'COVID-19 vaccines are not routinely recommended for children and young people under 18 years of age', although vaccination for at-risk under-18s could be reconsidered once more safety data is available.
People who are immunocompromised or HIV positive should be offered vaccination along with others in at-risk groups - with GPs delivering vaccination urged to consider also offering the vaccine to adult household members of people in these categories because of the likelihood of a reduced antibody response.
The guidance suggests that the priority list for vaccination has shifted slightly since the JCVI published an update in September, with patients considered 'clinically extremely vulnerable' - those asked to shield earlier in the pandemic - now in line for vaccination alongside patients aged 70 and over.
The first in line for vaccination remain residents and staff at care homes for older people, followed by over-80s and health and social care staff.
Over-75s would come next, with shielding patients and over-70s after them, followed by over 65s, then at-risk adults aged 18-65 - including those with chronic respiratory, heart, liver or other conditions, patients with diabetes and those who are morbidly obese. Patients aged over 60, then over 55s and finally people aged over 50 are the final groups in line for vaccination by GP-led clinics set up in each of England's 1,250 primary care network areas.
The guidance recommends at least a seven-day gap between adminstration of a COVID-19 vaccine dose and any other vaccination.
A gap of 21 days is required between doses of the Pfizer/BioNTech vaccine, and 28 days between doses of the Oxford/Astra Zeneca one - but government guidance suggests that for 'operational purposes' and to simplify the advice to the public, practices should schedule a 28-day gap between doses of whichever product they use.
There are significant differences between the two vaccines that will affect the logistical challenge they pose to providers. The Pfizer/BionTech vaccine needs to be stored at -70°C, lasts for six months and can be stored for five days at 2-8°C once thawed. It comes in batches of 975 doses, delivered in 195 five-dose vials and must be diluted before being administered.
The AstraZeneca vaccine should be stored at +2ºC to +8ºC and has a shelf life of 6 months. Once open, vials should be used within six hours when stored at room temperature or within 48 hours
when stored in a refrigerator. This vaccine is supplied in packs of 10 vials, each containing eight or 10 doses of vaccine.