COVID-19 vaccines and how they work in the UK

We’re amid the COVID-19 pandemic, and the race for a safe and effective vaccine allowed us to accelerate diagnostics and have developments in record times.

There are currently more than 50 COVID-19 vaccines in trial worldwide. So far, extensive studies on five vaccine candidates have been published, including the vaccines developed by Pfizer, Oxford/AstraZeneca, and Moderna, the vaccines currently approved in the UK and covered in this article.

A database of COVID-19 candidate vaccines can be found on the WHO website; it contains a summary of the vaccines in both clinical and pre-clinical development, and it’s regularly updated twice a week.

Types of vaccine

Vaccines are designed to allow the body to recognise and block viruses, and a few techniques can be used for the purpose:

Protein-based vaccines: These vaccines use fragments of protein that mimic the virus to create an immune response.
Inactivated virus vaccines: These vaccines use a form of the virus that has been inactivated or weakened to avoid the disease and still cause an immune response.
RNA / DNA vaccines: In these types of vaccines, genetically engineered RNA or DNA are used to create a protein that causes an immune response.
Viral Vector Vaccines: In these vaccines, a virus is genetically engineered to produce coronavirus protein, causing an immune response without the disease.

There is currently insufficient evidence that proves how long the vaccine will protect against COVID-19, but data is being evaluated and reported daily.

The Pfizer and Moderna vaccines are based on messenger RNA (mRNA) technology, whereas the Oxford/AstraZeneca is an adenovirus-vectored vaccine taken from a cold that infects chimpanzees.

Prices are also different among the three vaccines, as the Pfizer-BioNTech costs $20 per dose, Moderna’s vaccine costs $33 per dose, and the Oxford-AstraZeneca vaccine is available at $4 per dose.

For the post-administration period, vaccine providers should observe the patient for 30 minutes after administering the vaccine, should that person have a history of anaphylaxis or immediate allergic reaction.

All the other patients can be observed for 15 minutes post-vaccination to be monitored for possible adverse reactions.

Pfizer-BioNTech COVID-19 vaccine

The Pfizer-BioNTech vaccine (BNT162b2), developed by BioNTech SE, is an mRNA type of vaccine, and it’s given through intramuscular (IM) injection.

It includes two shots to be given at least 21 days apart and is authorised and recommended to people ages 16 years and older.

Early data show the efficacy of 95% in the prevention of COVID-19.

mRNA vaccines are not interchangeable; hence, both doses should be done with the same product.

With the current data available, no booster or additional doses are recommended, but both doses are necessary for protection, as the efficacy of a single dose hasn’t been evaluated yet.

This vaccine doesn’t contain eggs, latex, or preservatives, and it’s contraindicated to those who experienced severe allergic reactions, such as anaphylaxis, to an mRNA COVID-19 vaccine or its components, and to those who experienced an allergic reaction to polysorbate and polyethene glycol, due to the ingredient PEG. These people cannot receive this vaccine unless they have been evaluated by a specialist first and have been deemed safe to get the vaccination.

Common adverse reaction reported so far include:

Pain at the injection site
Fatigue
Headache
Muscle pain
Chills
Joint pain

The preparation should be mixed only with sterile 0.9% sodium chloride and gently inverted ten times before administration.

Each multidose vial contains a minimum of five 0.3 ml doses, as per FDA, a maximum of 6 doses per vial can be given, the remaining volume must be discarded. After preparation, the vaccine must be used within 6 hours.

Pregnant and lactating women can receive the vaccine.

This vaccine must be stored for six months at -80 °C to -60 °C. Once removed from the freezer, the undiluted vaccine can be stored for up to 5 days at 2 °C to 8 °C, and up to 2 hours at temperatures up to 25 °C, prior to use. After dilution, the vaccine can be stored at 2 °C to 25 °C and use as soon as practically possible and within 6 hours.

Moderna COVID-19 vaccine

The Moderna vaccine (mRNA-1273), developed in Massachusetts, is another type of mRNA vaccine, and it’s given as IM injection in the deltoid muscle.

It includes 2 shots to be given 28 days apart and is authorised and recommended to people ages 18 years and older, and both doses should be done with the same product.

Based on the early data, the vaccine has an efficacy of 94.1% in preventing COVID-19 infection in people who received the two doses.

The most common side effects reported include:

Pain, redness, and swelling at the injection site.
Fatigue
Headache
Chills

The vaccine cannot be mixed with a diluent as it doesn’t require reconstitution, and it contains ten 0.5 ml doses per vial.

Once taken from the refrigerator, the vial should stand at room temperature for 15 minutes; once opened, the vial should be used within 6 hours.

At this stage, a need and timing for a booster haven’t been established.

Pregnant and lactating women can receive the vaccine.

This vaccine must be stored at a -25ºC to -15ºC to remain stable for seven months, Once thawed, the medicinal product should not be re-frozen and may be stored refrigerated at 2 °C to 8 °C protected from light for up to 30 days if not used.

Oxford/AstraZeneca COVID-19 vaccine

The Oxford/AstraZeneca vaccine (ChAdOx1 S [recombinant]), developed in the UK, uses a different technology compared to the Pfizer and the Moderna one; this vaccine contains a replication-deficient chimpanzee adenovirus vector encoding the SARS CoV 2 Spike (S) glycoprotein.

Early data report efficacy of 70%, up to 90% if the dose is adjusted.

Is recommended to people aged 18 and older, and it’s administered through IM injection, preferably in the deltoid muscle. The second shot can be administered between 4 and 12 weeks after the first one, and both doses should be done with the same product.

Common side effects include:

Pain, redness, swelling at the injection site.
Fever
Fatigue
Headache
Muscle pain
Chills

Each vial contains 10 doses (0.5 ml each).

The vaccine must be stored in a refrigerator (from 2°C to 8°C).

The NHS vaccination programme

The vaccination programme started in the UK in December 2020, with the NHS being the first health system in the world to roll out a vaccine, and the process is proceeding at higher rates among hundreds of nursing homes, vaccination centres, and hospitals to deliver the doses available.

New sites have started to offer the vaccination service, including high street pharmacies, mosques, and cinemas as the vaccination programme accelerates.

A list of hospital hubs and local vaccination services is available on the NHS website.

Useful links

REFERENCES:

1- NHS.UK (2021). Available at <https://www.nhs.uk/conditions/coronavirus-covid-19/coronavirus-vaccination/coronavirus-vaccine/> [Accessed 16 Jan 2021]. Coronavirus (COVID-19) vaccine.

2- GOV.UK (2021) Available at <https://www.gov.uk/government/publications/regulatory-approval-of-pfizer-biontech-vaccine-for-covid-19 > [Accessed 18 Jan 2021]. Regulatory approval of Pfizer/BioNTech vaccine for COVID-19.

3- GOV.UK (2021) Available at <https://www.gov.uk/government/publications/regulatory-approval-of-covid-19-vaccine-astrazeneca> [Accessed 19 Jan 2021]. Regulatory approval of COVID-19 Vaccine AstraZeneca

4- GOV.UK (2021) Available at <https://www.gov.uk/government/publications/regulatory-approval-of-covid-19-vaccine-moderna> [Accessed 21 Jan 2021]. Regulatory approval of COVID-19 Vaccine Moderna.