Pfizer COVID-19 vaccine: Does it stop you getting COVID? Will it make you immune? Everything you need to know

New Zealand will receive its first batch of COVID-19 vaccines next week, with frontline border workers first in the queue.

Their household contacts are next in line, followed by healthcare workers, essential workers and those in groups at risk of serious illness or death. The rest of us will get ours later in the year.

If you've been following the development of vaccines against the coronavirus, you'll be aware there are several - and that they work in different ways. The Government has deals in place to buy four of them - one developed by US-based Pfizer and Germany's BioNTech; another by Belgium's Janssen Pharmaceutica;  a third by US company Novavax and the fourth a collaboration between the UK-Swedish firm AstraZeneca and the University of Oxford. 

The first to arrive on our shores is the Pfizer-BioNTech vaccine. Here's everything you need to know about it.

The vaccine is called tozinameran and is sold under the brand name Comirnaty.
The vaccine is called tozinameran and is sold under the brand name Comirnaty. Photo credit: Getty

What is it, exactly? And how does it work? 

The vaccine, called tozinameran and sold under the brand name Comirnaty, is a new kind of vaccine that doesn't involve injecting the patient with any existing virus material. Traditional vaccines typically introduce weakened or inactivated versions of the virus they aim to protect against into the body, which learns what they look like so they can fight off a full-strength infection. 

Tozinameran instead uses a brand new technology called mRNA, short for messenger RNA. 

"They teach our cells how to make a protein - or even just a piece of a protein - that triggers an immune response inside our bodies," according to the US Centers for Disease Control and Prevention (CDC). "That immune response, which produces antibodies, is what protects us from getting infected if the real virus enters our bodies."

Another vaccine, Moderna's mRNA-1273, also uses the new technology. The others New Zealand has bought are adenovirus vector and subunit vaccines, the technology of which has been around for decades.

How well does the Pfizer-BioNTech vaccine work? 

Based on the clinical, peer-reviewed phase three trials, extremely well. Tens of thousands of people received either the vaccine or a placebo, and by the time it was over, those who received two shots of the vaccine were about 20 times less likely to have caught COVID-19.

In comparison, the MMR vaccine - which has a long and proven track record - is 97 percent effective against measles and 88 percent effective against mumps, according to the CDC, and the chicken pox vaccine about 92 percent effective.

Tozinameran and Moderna's similar mRNA vaccine have had some of the best clinical trial results of any of the vaccine candidates to date, despite using cutting-edge, previously unproven technology. The stunning results actually surprised experts, many of whom thought it would take much longer - possibly years - to develop a working vaccine.

How long does the vaccine take to work?

Tozinameran requires two shots to reach its maximum efficacy of 95 percent. They are delivered about three weeks apart. The immune response reportedly starts to pick up around two weeks after the first injection in the young and middle-aged, and after three weeks in the elderly. 

The 95 percent efficacy measurement is at one week after the second dose.  

Do I need two shots? Or will one do? 

It's not clear how protective a single shot is. Some jurisdictions facing widespread outbreaks - such as the UK - have considered delaying second shots so more people can get at least some protection; this week promising data was released by UK health authorities suggesting it could give about 66 percent protection - enough to bring daily hospitalisations down - but it's still early days.

Some epidemiologists fear however the weaker immune response a single-shot generates could prompt faster evolution of the virus, giving rise to mutations that make it even stronger. 

The Janssen vaccine that might be on offer to Kiwis later this year was designed to be single-shot from the start. The Novavax and AstraZeneca vaccines both require two shots.

Who is eligible for the Pfizer-BioNTech vaccine?

As mentioned above, frontline border workers and their household contacts will be first, followed by healthcare workers, essential workers and those in high-risk groups. The rest of us should be able to get it in the second half of the year. 

Medsafe has approved the vaccine to be used in people 16 and over. 

Is the Pfizer-BioNTech vaccine safe? 

Tozinameran has not only undergone rigorous clinical trials, it has been scrutinised by various medical authorities around the world, who have all deemed it safe for the vast majority of people. 

Of course, with any vaccine there are going to be exceptions - while trials involve tens of thousands of people, there are more than 7 billion of us, all different. 

"The known and potential benefits outweigh the known and potential risks of the vaccine's use," the US Food and Drug Administration said, in giving the vaccine emergency approval to fight the outbreak there which has killed hundreds of thousands.

There is conflicting advice on whether pregnant or lactating mothers should receive the vaccine. They weren't part of the trial, and the World Health Organization is currently recommending they don't get it, but others - such as the CDC - say it should be fine, as there's nothing in the vaccine known to be a risk factor for them. 

"It's important to remember that this vaccine has not been fully tested in some populations such as children under age 16, pregnant women or some immunocompromised groups, so more clinical trial data is needed for these groups," said Fran Priddy, clinical director of Vaccine Alliance Aotearoa New Zealand.

People who have had COVID-19 before and recovered can still get vaccinated, the CDC says - there have been cases of reinfection that the vaccine could prevent, and it's not known how long natural immunity lasts. 

There is no evidence of any deaths caused by the vaccine itself. Six died during the trial, but most - four - had received the placebo. None were directly linked to the trial. There have been reports of deaths in homes for the elderly after residents were vaccinated, but a WHO inquiry found they were "in line with the expected, all-cause mortality rates and causes of death in the sub-population of frail, elderly individuals".

"New Zealand has the important advantage over the US and Europe of being able to take advantage of their experience with many millions of doses," said Peter McIntyre, medical advisor at the Immunisation Advisory Centre.

After 12 million doses in the US, there had only been 590 reported serious adverse events.

If you're in doubt about whether you should get the vaccine, ask your doctor for advice. The WHO has a more complete list of at-risk groups on its website

What are the side-effects? 

In the trial, minor side-effects were common - in order, participants reported pain (>80 percent), fatigue (>60 percent), headache (>50 percent), myalgia and chills (>30 percent), arthralgia (>20 percent), pyrexia and injection site swelling. About one in every 90,000 people who's received a dose so far has reported an allergic reaction, according to the CDC, mostly in people with a history of allergies. 

None of these figures are outside the norm for vaccines. 

Director-General of Health Ashley Bloomfield.
Director-General of Health Ashley Bloomfield. Photo credit: AM Show/Getty

Does it stop transmission?

While most vaccines that prevent the recipient from falling ill of a disease also stop its transmission, it's not known for sure whether this is the case with COVID-19 - but it's likely. 

Will I need booster shots? 

At this stage, no one knows. COVID-19 is a relatively new disease, the vaccines even newer, and it's not clear just how long the immune system remembers the virus. Also, no one knows how the SARS-CoV-2 virus which causes the disease is going to mutate in the future - there is early evidence a mutation first seen in South Africa, and now appearing in the UK, helps it evade the current vaccines on offer. 

Some experts think we might have to develop new COVID-19 vaccines every year, just like we do with the flu. 

Do I have to get this vaccine?

No one in New Zealand will be forced to get the Pfizer-BioNTech vaccine, nor any others. Newshub enquired with the Ministry of Health earlier this week as to whether Kiwis would be able to choose which vaccine they got, once more were available, but is yet to get an answer.

If you can get a vaccine, it would be wise to do so - not just for yourself, but those who can't for whatever reason (eg. age, medical reasons). It's not clear yet what level of the population will need to be vaccinated to achieve herd immunity, but the more the better. 

Does the vaccine contain microchips? 

If you don't already know the answer to this, I'm surprised you've made it this far into the article - the answer is no.