COVID-19 vaccination programme: Information for healthcare practitioners
The COVID-19 mRNA Vaccine BNT162b2 uses an mRNA platform and the AstraZeneca COVID-19 vaccine is an adenovirus vector vaccine.
Both vaccines are presented in multi-dose vials and require completion of a two-dose course. Using multi-dose vials can improve the efficiency of vaccine manufacture and distribution, enabling vaccine availability for those eligible at the earliest opportunity.

COVID-19 mRNA Vaccine BNT162b2 (Pfizer-BioNTech)
The COVID-19 mRNA Vaccine BNT162b2 is an mRNA (messenger ribonucleic acid) vaccine. It contains the genetic sequence (mRNA) for the spike protein which is found on the surface of the SARS-CoV-2 virus, wrapped in a lipid envelope (referred to as a nanoparticle) to enable it to be transported into the cells in the body.
When injected, the mRNA is taken up by the host’s cells which translate the genetic information and produce the spike proteins. These are then displayed on the surface of the cell. This stimulates the immune system to produce antibodies and activate T-cells which prepare the immune system to respond to any future exposure to the SARS-CoV- 2 virus by binding to and disabling any virus encountered.
As there is no whole or live virus involved, the vaccine cannot cause disease. The mRNA naturally degrades after a few days.

Clinical trials
The safety and immunogenicity of the COVID-19 mRNA Vaccine BNT162b2 has been evaluated in clinical trials in six countries: US, Germany, Brazil, Argentina, South Africa and Turkey.
Over 44 000 participants have taken part in the clinical trials of this vaccine. Half of the participants received the COVID-19 vaccine and the other half received a placebo vaccine. Results from the phase three clinical trials suggested the vaccine can prevent 95% of vaccinated adults from getting COVID-19 and that the vaccine works equally well in people of all ages, races and ethnicities. The observed efficacy in adults over 65 years of age was over 94%.

AstraZeneca COVID-19 vaccine
AstraZeneca COVID-19 vaccine is a viral vector vaccine which uses a weakened adenovirus as a carrier to deliver the SARS-CoV-2 antigen. The adenovirus has been modified so that it cannot replicate (grow and multiply by making copies of itself) in human cells and therefore cause any disease.

COVID-19 vaccination programme: Information for healthcare practitioners
The genes that encode for the spike protein on the SARS-CoV-2 virus have been inserted into the adenovirus’s genetic code to make the vaccine. When the vaccine is injected, it enters the host’s cells which then manufacture the spike protein. This then stimulates the immune system which reacts by producing antibodies and memory cells to the SARS-CoV-2 virus without causing disease.

Clinical trials
Trials of the AstraZeneca COVID-19 vaccine showed that it produced neutralising
antibodies in Rhesus macaques as well as a reducing the amount of detectable virus in

the lower respiratory tract following challenge with SARS-CoV-2 .
In human trials, the
vaccine was compared with a placebo vaccine in healthy adults aged between 18-55 years. Preliminary findings show that neutralising antibodies were induced after the first vaccination and that levels of these increased after a second dose. Specific T cell responses were also induced after a single immunisation and were maintained after the second dose. Data showed that spike antibody responses and neutralising antibody 28 days after the second dose were similar across the three age cohorts (18–55 years, 56– 69 years, and ?70 years). More than 99% of the participants had neutralising antibody responses two weeks after the booster dose. Peak T-cell responses were seen 14 days
after the first dose and were broadly equivalent in the three age groups .
Further clinical trial data for both of these vaccines will be added when this becomes available.

Interchangeability of different COVID-19 vaccines
There is no evidence as to the interchangeability of the different COVID-19 vaccines although studies are underway. Therefore, every effort should be made to determine which vaccine the individual received and to complete with the same vaccine.
For individuals who started the schedule and who attend for vaccination at a site where the same vaccine is not available, or where the first product received is unknown, it is reasonable to offer a single dose of the locally available product. This option is preferred
COVID-19 vaccination programme: Information for healthcare practitioners
if that individual is likely to be at immediate high risk or is considered unlikely to attend again. In these circumstances, as both the Pfizer-BioNTech and AstraZeneca vaccines are based on the spike protein of the virus, it is likely that the second dose will help to boost the response to the first dose. Further doses of vaccine are not required unless additional information becomes available.

Part 2 to follow