Vaccine’s reduced efficacy against COVID variant ‘worrying’

Doug Hendrie

8/02/2021 6:26:03 PM

South Africa has paused its rollout of the Oxford University/AstraZeneca coronavirus vaccine. What does this mean for Australia?

Graphic representing coronavirus mutation.
Multiple vaccine developers have seen lower efficacy in trials of their candidates against the 501Y.V2 variant.

‘This is a worrying development. This is something to be taken seriously and thought through.’
That is University of Sydney vaccine expert Professor Robert Booy, responding to South Africa’s move to suspend its rollout of Oxford University and AstraZeneca’s COVID-19 vaccine candidate, AZD1222.
The decision to pause one millions doses of the vaccine is related to concerns about reduced efficacy in preventing mild and moderate disease from a threatening new variant that has already been shown to affect efficacy in other candidates.
Fellow vaccine manufacturers Novavax and Johnson & Johnson have both seen lower efficacy in trials of their vaccines against the 501Y.V2 variant, which first emerged in South Africa and has been linked to the country’s fast-moving second wave.
This variant shares key polymorphisms with a separate variant that emerged in Brazil, with both variants leading to a wave of reinfections – suggesting immunity from the first infection does not offer long-lasting protection.  
‘The very real concern is that protection against this new variant may not be very good either for mild or severe disease,’ Professor Booy told newsGP.
‘The vaccines proposed in Australia should be protective against severe disease, while we have standard COVID variants – including the UK variant. But it’s very important we prevent the South African variant from taking over in Australia.
‘This virus is a significant foe. There have never been more active infections in the world then there are right now. This increases the risk of virus mutation to a form that may be more transmissible and less likely to be prevented by [a] vaccine.

‘We just have to adapt the vaccine the same way the virus adapts its genetics. A year from now, it’s possible we could have vaccines that cover more than one variant, and vaccines that offer one kind of protection for the first dose and a slightly different protection in a booster.’
But other experts, such as prominent infectious disease researcher Dr Müge Çevik, have cautioned that the data is early – and that trials of these vaccines against the South African variant still broadly suggest they are effective at the top priority task of reducing severe disease, hospitalisations and deaths. Reduction of mild and moderate disease is regarded as secondary.  

The news may pose a challenge locally, given Australia’s reliance on the AstraZeneca vaccine, which is expected to be administered largely by GPs with a rollout flagged for early March. Australia has bought almost 54 million doses.
At a press conference on Monday, Health Minister Greg Hunt moved to address fears over the news, noting advice from Department of Health experts indicates there is ‘currently no evidence to indicate a reduction in the effectiveness of the AstraZeneca or Pfizer vaccines in preventing severe disease or death’.
‘The world, however, is reviewing data with regards to the impact on transmission of mild-to-moderate symptoms and we will be looking at the latest data,’ he added.
In a response to a report in the Financial Times, an AstraZeneca spokesperson said early data had shown ‘limited efficacy’ against mild disease due to the B.1.351 South African variant, but that the young age of the subjects meant its effectiveness against severe disease and hospitalisation remains unknown.
However, a spokesperson later told the newspaper the company believes AZD1222 could provide protection against severe disease.
‘Neutralising antibody activity is equivalent to that of other COVID-19 vaccines that have demonstrated activity against more severe disease, particularly when the dosing interval is optimised to 8–12 weeks,’ the spokesperson said.
Professor Jamie Triccas, who heads the infectious diseases and immunology discipline at the University of Sydney, told newsGP that while preliminary, the AstraZeneca results appear similar to the experience of other vaccines tested against the South African variant.
‘In South Africa, around 90% of cases appear to be the new variant. It’s difficult to know how widespread this variant will be and if it will be particularly problematic for us,’ he said.
Professor Triccas said that while data for the AstraZeneca vaccine remains limited, it appears that overall, vaccines tested against the South African variant have lower overall efficacy.
But he stresses that other vaccines still appear to protect against severe disease and hospitalisations. 
Kirby Institute virologist Associate Professor Stuart Turville told newsGP that the rollout of existing vaccines should be done as quickly as possible to slow the advances of the variants.
‘A lot of this is happening in real time. It’s happening so fast. We have to slow its momentum now,’ he said.
‘By slowing it down [through vaccinations], we can make the variant of the future five years away, rather than talking about it now.
‘We have to take note of what’s happening in Israel, where their rollout is blunting the ability of the virus to really take hold in communities. They’ve really hit their stride with vaccination, and they’re reporting back in real time.
‘In heavily vaccinated communities, they’re seeing people report less infection and less pressure on their hospitals.’
A new preprint analysing the nationwide rollout by Israeli researchers found coronavirus cases and hospitalisations began to decline in January, with larger and earlier decreases found in towns vaccinated earlier.
Prominent epidemiologist Professor Mike Toole told newsGP the early data suggests it was not premature for South Africa to stop the rollout.
‘South Africa has alternatives like Pfizer, and they’ll be open to looking at other vaccines,’ he said.
However, infectious diseases expert Professor Peter Collignon said the new data has a very large error range.
‘So far, this seems like an overreaction – the numbers are based on a very small dataset with wide confidence intervals,’ he told newsGP.
‘It seems precipitous and not based on enough data.
‘The main point of vaccines is that we need to stop people dying or getting serious illness, and all vaccines are much better than I would have expected at that – ranging from 70–90% efficacy.
‘Are they as good at stopping mild illness or transmission? No, they’re not as good – but if we get a decrease of 50%, that’s still good. None will be perfect in the first instance.’
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