The Whole Truth: Covid-19 Vaccination | By Stuff reporter Nikki Macdonald
First, there was a variant in the UK. Then South Africa birthed another mutation. In Brazil, a new breed of the virus swamped hospitals with casualties. And the latest case surge in India has prompted the World Health Organisation to designate another “variant of concern”.
As the virus that causes Covid-19 (SARS-CoV-2) spreads around the world, it mutates. It’s like gossip - the further the story spreads, the more mistakes creep into the retelling.
Most mutations don’t have a big impact. But significant changes could erode the effectiveness of vaccines.
Vaccines work by training the immune system to identify and fight off invaders. But if the virus’s structure strays too far from the blueprint provided by the vaccine, then the virus could sneak behind the body’s defences, without being recognized.
Covid-19 vaccines target the SARS-CoV-2 spike protein, which the virus uses to bind to host cells and infect its victim. So virus variants with mutations in that spike protein present the biggest threat to vaccine effectiveness.
So what do we know about the variants that have emerged so far?
The Alpha/UK variant, which has the technical name B.1.1.7, popped up in September 2020 and proved more infectious than the original Wuhan strain. But it doesn’t seem to block the effectiveness of the Pfizer BioNTech vaccine being rolled out in New Zealand.
Data from Israel, where the Alpha variant was dominant, showed the Pfizer vaccine gave more than 95 percent protection against both infection and serious disease.
A laboratory study showed the P.1/Gamma strain that brought Amazonian city Manaus to its knees, also still responds to the Pfizer BioNTech jab.
The Beta strain, which emerged in South Africa is more problematic. That strain emerged in October 2020 and is known as B.1.351.
Real-world evidence from Qatar found the Pfizer-BioNTech jab was less effective against the Beta strain. It protected 90 percent of fully vaccinated people against infection with the UK variant, but that dropped to 75 per cent for the South African virus version.
But importantly, the vaccine still gave almost complete protection against severe disease for both strains.
The latest mutation to be labelled a variant of concern by the World Health Organisation (WHO) is the B.1.617/Delta strain first found in India in October 2020.
An early study by Public Health England - not yet peer-reviewed - showed that two doses of the Pfizer vaccine were 88 percent effective at preventing symptomatic disease from the Delta strain.
If more mutations occur, manufacturers might need to tweak the vaccine. The design of mRNA vaccines such as the Pfizer jab should make them relatively easy to alter.
Pfizer and BioNTech are also investigating whether a third dose could boost immunity to virus variants.
If the virus keeps changing, regular update jabs might be needed, such as with the annual ‘flu vaccine. That formula changes slightly every year, depending on which variants of the disease are circulating.
Reporting disclosure statement: This article was reviewed by The Whole Truth: Covid-19 Vaccination expert panel member, Professor David Murdoch.