Delta variant means COVID-19 vaccination rates must be higher, says public health expert

The Delta variant means countries can no longer hope to achieve herd immunity by vaccinating 60-70% of people against COVID-19, as is the case with other diseases, according to a leading public health expert.

Professor Devi Sridhar

Professor Devi Sridhar, chair in global public health at the University of Edinburgh, told the RCGP annual conference that COVID-19 variants had been the 'main challenge of 2021' for most countries.

She said that even New Zealand 'with all their sequencing, their tracing, their tech, were not able to eliminate [Delta], even with harsh lockdowns. It's that transmissible. China is the only place now which is still aiming for zero COVID given how transmissible Delta is.'

'The idea that we can just vaccinate to a threshold of 60 or 70% and completely stop transmission, the way we've done with measles, or mumps, and rubella just doesn't seem practical anymore with Delta,' Professor Sridhar said.

'And so we have to vaccinate and protect people not because of this idea of herd immunity, but for their own protection for themselves. And to make sure they're healthy and then not passing on to others.'

COVID-19 predictions

Professor Sridhar's comments came in a presentation on what scientists could and couldn't predict about the COVID-19 pandemic.

She said one of the things she couldn't have predicted about the early pandemic in the UK was 'how many debates we would have about who matters and what lives matter'.

Professor Sridhar said she watched and took part in debates focused on 'should we just let old people die? People who have cancer - are their lives worth less?'

'These debates did not take place in other parts of the world. These debates did not take place in Hong Kong or Singapore. There was never the question of should we sacrifice this for others,' she said.

'We were missing the core of the issue, which is how do we work together as a society, as a community, caring for each other, to make sure we can keep as much of the economy open with as little infection as possible,' Professor Sridhar said.

'That was the puzzle - not whether we should get rid of some people and keep others and whose lives were worth more.'

Economy vs health

She argued that choosing between the economy and health was a false choice. 'If you suppress the virus people want to consume more, [because] they have more trust in the economy,' Professor Sridhar said.

'So actually while lockdowns in the short term carried a harm if you could build in other ways to suppress the virus - test and trace, border measures, masks, ventilation, all the other things you can do - you could actually keep businesses open,' she said.

Sweden, which took much longer than other countries to impose any sort of lockdowns or restrictions, suffered a greater loss of life but the economic costs were broadly similar to other countries, Professor Sridhar said.

Professor Sridhar also revealed that she was working with the US government on the 100 Days Mission, an international drive launched at the G7 meeting in the UK earlier this year to reduce the impact of future pandemics by making diagnostics, therapeutics and vaccines available within 100 days.

'This is the idea that when the next pandemic happens there will be sequencing done on the pathogen, and within 100 days jabs will go into arms using the new mRNA technology,' she explained. 'And so figuring out how what would usually take five years, we did it in a year [for COVID], how can you make that even less, which is 100 days.'

She added that her work on the project was looking at society and public health in future pandemics, including how to keep schools and businesses open, whether more robust test and tracing was required and public communications.

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