Humans and Health

How Does The Pfizer/BioNTech Vaccine Work?

Sarvenaz Hosseini

The news has been full of reports about the new vaccine from Pfizer/BioNTech. But how does it actually work? Impact writer and Pharmacy PhD student, Sarvenaz Hosseini explains.

How Do Vaccines Work?

Vaccination involves introducing the body to a weakened or inactivated pathogen so that in the future when the immune system comes across that pathogen, the infection is less severe than what it would have been without vaccination. Through vaccination, the immune cells in our bodies produce highly specific antibodies for the specific disease.

mRNA vaccines provide our cells with a recipe to make a protein or part of a protein which triggers an immune response

If the vaccine is effective enough, the immune system can memorise the recipe to produce the antibodies. So that when the actual virus or bacteria enters our bodies, the antibodies are quickly produced, flagging the area, and notifying our immune system to kick into action by neutralizing and destroying the pathogen.

There are many different types of vaccines which each have slightly different ways of achieving immunity in the patient.

The Pfizer/BioNTech vaccine is a novel type of vaccine called a messenger RNA (mRNA) vaccine and is thought to be a trailblazer for future vaccines. mRNA vaccines provide our cells with a recipe to make a protein or part of a protein which then goes on to trigger our immune system into producing antibodies.

How Does the Pfizer/BioNTech Vaccine Work?

Our immune cells recognise that the spike protein does not belong to our own bodies and starts making antibodies

The Pfizer/BioNTech vaccine (catchily named BNT162b2) contains the recipe for a harmless part of COVID-19 called the spike protein. Harmless yet mighty, the spike proteins on the surface of COVID-19 are what gives the virus its characteristic aesthetic and coincidentally is what allows the virus to enter our cells.

A model of the COVID-19 spike protein in the foreground, with a model of the coronavirus in the background

A model of the COVID-19 spike protein

To enter our cells, COVID-19 uses its spike protein to attach to receptors on our cells called ACE2. Once attached, COVID-19 can enter our cells and wreak havoc by hijacking our cell machinery to replicate itself until our cells burst, releasing new copies of COVID-19 and the cycle repeats itself until our immune system has the chance to catch up or sadly sometimes not.

Once the Pfizer/BioNTech vaccine is injected into the upper arm muscle, the recipe (mRNA) for the spike protein enters muscle cells which results in the production of the spike protein (ref and ref). The recipe, aka the mRNA, is then broken down and destroyed through natural mechanisms that already exist in our bodies.

After this, the muscle cell shows the spike protein on its surface (like a chef showing off the dish they have made). Our immune cells recognise that the spike protein does not belong to our own bodies and starts making antibodies against the spike protein.

mRNA vaccines are extremely fragile and easily breakdown

All the while the immune system also memorizes the shape of the spike protein so that when it comes across it in the future, it can quickly act to deploy fighter immune cells. The result of all this being a chance of immunity against COVID-19 without the risk of getting infected with COVID-19 itself.

How Effective Is This Vaccine?

Once they have received the Pfizer/BioNTech vaccine, those who get exposed to COVID-19 after 28 days have a 95% chance of being able to effectively fight off the infection based on a large-scale study involving 43000 participants at 150 different clinical trial sites in the US, Germany, Turkey, South Africa, Brazil, and Argentina. The trial will continue to monitor and collect data from the participants for an additional two years.

How Easy Is the Vaccine to Distribute?

The only barrier that remains for our BNT162b2 Pfizer/BioNTech vaccine remains a logistical one. mRNA vaccines are extremely fragile and easily breakdown. This one needs to be kept in a specially designed container with dry ice at a temperature of -70 °C which would need re-icing every 5 days to have a shelf life of only 30 days.

Once taken out of the special vessel, it can only be stored for 5 days at normal fridge temperatures. This obviously creates major logistical issues with the roll-out especially when we have bought 40 million doses; equating to 20 million full vaccinations as 2 doses are required for a full response. We can only wait and see. It is the COVID way.

Sarvenaz Hosseini

Featured image by Marco Verch Professional Photographer from Flickr (original). Image licence found here. No changes made to this image.

In article image by NIAID from Flickr. Image license found here. No changes made to this image.

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