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Pfizer vaccine 101: How it works, its side effects and New Zealand's rollout

As New Zealand continues its rollout of the Pfizer Covid-19 jab, a leading vaccine expert says there’s still a lot to learn about them. 

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Graham Le Gros of the Vaccine Alliance Aotearoa says there’s still a lot to learn about the jab. Source: Breakfast

But the Pfizer Covid-19 vaccine in particular is so far proving effective, Graham Le Gros of the Vaccine Alliance Aotearoa says.

The Malaghan Institute of Medical Research professor answered some frequently-asked questions on Breakfast this morning.

How effective is the Pfizer Covid-19 vaccine?

Le Gros says overseas data find the vaccine is about 95 per cent effective in preventing a severe case of Covid-19 . 

“Pfizer is looking fantastic” when it comes to combatting most variants of the disease, although emerging data shows it may not be as effective against the variant first detected in South Africa, he says.

“This is a really great vaccine … We’re in good shape at the moment and we’re lucky to have taken this vaccine.”

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Dr Joe Bourne says border workers' household contacts are next in line to get a jab. Source: 1 NEWS

Efficacy describes how well a vaccine prevents disease, and possibly also transmission, in ideal and controlled circumstances by comparing a vaccinated group of people with a placebo group. Effectiveness, on the other hand, refers to how well a vaccine performs in the real world. 

How does the Pfizer Covid-19 vaccine work?

Covid-19 mRNA vaccines work by training the body’s immune system to recognise the virus by telling cells to create a harmless “spike protein”, similar to the one found on the surface of the virus that causes Covid-19. It doesn’t alter a person’s DNA while it does so, and is quickly flushed out of the body. 

“Often we make immune responses to all the other parts of the virus which actually don’t matter a heck to the virus. You actually have to target the bit of the virus that the virus uses to get inside our cells and start growing,” Le Gros says. 

He says because mRNA vaccines only focus on Covid-19’s spike protein, it results in “very few side reactions” while proving to be “very effective” in “stopping the virus dead in its tracks”.

What are its side effects?

Le Gros says because every person is different, side effects can vary. But serious reactions are few and far between, only happening in about one in a million people. 

More common reactions to the Pfizer Covid-19 jab can include sore arms, some spots, mild flu-like symptoms and headaches, he says. 

“That’s your immune system kicking in and responding the way we want it to respond.”

Can it stop the transmission of Covid-19?

Le Gros says it’s too early to tell for sure to what degree Covid-19 vaccines stop transmission. But because vaccines reduce symptoms, it likely helps to stop transmission. 

He says it will take about five to 10 years to know for sure how long the vaccine will protect someone against Covid-19. 

How much of the New Zealand population should get vaccinated?

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The advisory group will face a number of decisions with NZ borders and public health settings after the nation has been vaccinated. Source: Breakfast

If people are happy to continue with social distancing and hygiene practices, the target could fall between 60 to 70 per cent, he says. 

“It depends on how we want to live our life. If we enter a rave party, we would need to have 100 per cent … vaccination.”

Le Gros says he’s hesitant to give a target lower than 100 per cent because some people would then choose to wait for others to get vaccinated instead. 

“The more people that do it, the safer all our vulnerable members of our community are.” 

Is New Zealand’s Covid-19 vaccine rollout slow?

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New Zealand is second to last in the OECD for its vaccination rollout per capita, but Jacinda Ardern says it's still going according to plan. Source: Q+A

Le Gros says the country was doing “OK”, but he wants to see a clearer plan going forward. 

He says the country is in a unique position because Covid-19 isn’t rampant, meaning it can take a measured approach. 

“The slower we can do it and the slower we can roll it out for New Zealand, the safer it is because we can see what’s going on overseas.”