It doesn't change our genes
It's true that the Pfizer-BioNTech vaccine involves genetic material - but that doesn't mean it can modify our own.
Let's start with how mRNA vaccines work.
All cells and many viruses use DNA as a kind of master set of instructions, and to carry them out, they're translated into a simpler molecule, called RNA.
Some viruses only contain RNA, and one of them is the coronavirus SARS-CoV-2 which causes Covid-19.
In extracting viral RNA and running it through genomic sequencing, for instance, scientists have been able to untangle different strains that have arrived in New Zealand, and trace the sources of outbreaks.
For vaccine makers, mRNA has proved an attractive option because, unlike DNA - which has to be somehow inserted into a cell's inner-most part, or its nucleus, for the vaccine to work - RNA can be translated into protein as soon as it reaches the thick solution each cell is filled with, called cytoplasm.
Perhaps the most beautiful part of these vaccines is how the mRNA is transported to the cells in the first place.
Scientists have pioneered lipid nanoparticles, which form tiny droplets that protect the RNA molecules as they're shuttled to their destinations.
What happens once they arrive?
RNA vaccines typically introduce an mRNA sequence - or the specific molecule that instructs our cells what to build - which is precoded for an antigen specific to a disease.
In the case of SARS-CoV-2, this was the "spike protein" the virus uses to attach itself to cells - and plays a big part in how quickly it spread within us, and to other people.
Packed inside Pfizer and BioNTech's BNT162 vaccine is the genetic material needed to grow the spike protein.
Once our cells produce and display this protein, it attracts and activates T cells - the roving hunters and killers of our immune system - and other immune cells.
The reason our body recognises the protein as something to get rid of is because our bodies recognise the SARS-CoV-2 spike protein as foreign.
In addition, the viral genetic material contained special features that animals have evolved to recognise as dangerous - helping draw attention to or enhance the immune response.
Ultimately, the process generates an immune response that the body remembered if it ever came into contact with the actual virus - and made us into our own vaccine factories.
Contrary to false claims widely shared on social media, mRNA vaccines don't genetically modify humans - nor do they create any genetically modified organism.
That's because they don't have access to the human genome, which is tucked away in the cells' nucleus.
As Pfizer describes it: "mRNA is a transient carrier of information that does not integrate into human DNA."
It doesn't give you Covid-19
No vaccine can cause a patient to develop the disease against which they were vaccinated, and this one isn't any different.
"It's impossible," University of Auckland vaccinologist Associate Professor Helen Petousis-Harris said.
"There are no infectious agents in the vaccine, or involved in its creation."
It is true that many vaccines contain bits of the viruses they guard against.
For instance, typical influenza shots we're more used to - viral vector vaccines - use pieces of a pathogen to effectively stimulate an immune response against it.
That spike protein then generates an immune response to the virus to potentially prevent infection.
The vaccine doesn't allow the SARS-CoV-2 virus to replicate and it cannot cause any known illness.
So what is in the vaccine?
It has both synthetic, or chemically produced, components and enzymatically produced components from naturally occurring substances such as proteins.
Its inactive ingredients include potassium chloride, monobasic potassium, phosphate, sodium chloride, dibasic sodium phosphate dihydrate, and sucrose, as well as small amounts of other ingredients.
The side-effects won't kill you
Like many other vaccines, Pfizer's shot can come with some potential side-effects.
They include injection site pain and swelling, fatigue, headache, muscle pain, chills, joint pain, fever, nausea, malaise, and lymphadenopathy - or the enlargement of the lymph nodes.
But - and again, contrary to disinformation swirling on social media - there's no major health risk that comes with getting a shot.
Although Pfizer didn't test its vaccine on people with a history of severe adverse or allergic reactions to a vaccine or a vaccine ingredient, there were no safety signals of concern identified in its clinical trials.
While some allergic reactions have been reported following vaccination, Pfizer was closely monitoring these, and recommended that appropriate medical treatment and supervision should always be readily available in case of a rare anaphylactic event.
Pfizer's clinical trials also didn't include pregnant women, and this group would be looked at more closely in a study that began earlier this year.
However, no serious concerns have been flagged - and research has also suggested that having the virus itself during pregnancy wasn't linked to adverse pregnancy outcomes.
Despite other claims, there's also no suggestion that the vaccine can cause Bell's palsy - a typically temporary condition that affects the nerves controlling facial muscles and, which can occur after a viral infection.
Petousis-Harris said she'd seen claims circulating on social media that the vaccine was associated with death.
Some of those claims were arising from people misinterpreting data contributed to official sites like the US Vaccine Adverse Event Reporting System.
"They are misusing this data and posting it all over the place, as proof that vaccines have caused all of these deaths," she said.
"These are people who've died after having the vaccine, yet it's been reported they didn't die because of the vaccine."
As an extra layer of protection, all vaccines used in New Zealand undergo Medsafe approval, which involves a thorough assessment to ensure they meet international standards and local requirements for quality and safety.
And that assurance still stood despite the rapid pace of Covid-19 vaccine production, the Ministry of Health said.
"We're moving swiftly but without taking any shortcuts or compromising safety."
