UK 'to hit herd immunity next week' as vaccines break the link between cases and deaths

New study finds fatalities decreasing even as drop in infections stalls

The UK will reach the threshold of herd immunity against Covid-19 on April 12, according to modelling by University College London, as vaccines “break the link” between cases and deaths.

The Office for National Statistics said the number of weekly coronavirus deaths in England and Wales had fallen by 92 per cent from the peak of the second wave.

The latest figures covering the week ending March 26 showed 719 deaths in a week, down from 8,945 from a week in January. On January 19 alone - the UK's deadliest day of the pandemic - 1,358 people died with Covid-19.

Scientists said the proportion of people who have protection against the virus – either through vaccines, previous infection or natural immunity – will hit 73.4 per cent next Monday, the same day non-essential shops and outdoor hospitality reopens.

Prof Karl Friston from UCL told The National that the UK's current threshold for herd immunity was 72 per cent.

"When you add to both the vaccine-induced immunity and natural immunity through previous infection and a small proportion of people who might have pre-existing or innate immunity - which could be up to 10 per cent - you can see immediately there aren't many people left.

"Suffering the Christmas surge and the success of the vaccination campaign has put us in a good position for reaching the threshold of herd immunity."

A separate study by Imperial College London found infections had fallen by about 60 per cent since February – but the data suggests the decline is levelling off.

While the decline in cases had stalled – possibly caused by the reopening of schools and increased social mixing – deaths did not follow the same pattern.

Between February 4 and February 23, when the React study was last carried out, an estimated one in 200 people had the virus.

It represented a two-thirds fall since January, with the decline attributed to lockdown.

With restrictions beginning to lift, it means scientists can now identify the decreases being driven by vaccination.

UK Health Secretary Matt Hancock said the results showed vaccines were preventing deaths even as the decline in cases was slowing.

“We’re seeing that the vaccine is working, it’s breaking the link between cases and deaths,” he said on Thursday.

“The number of people dying from Covid halved again in the last nine days."

He was keen to play down the findings on herd immunity being achieved by next week.

“I was told by some scientists that we were going to have herd immunity in May and then in June and then after that,” he said.

“What I prefer to do is watch the data. We’ve set out the roadmap, the roadmap is really clear. It is our route back to normal.”

Antibody testing by the Office for National Statistics suggested in the week ended March 14 that about 54 per cent of people in England had antibodies to the virus.

Since that study, a further 7.1 million people received the first dose of a Covid-19 vaccine, bringing the total number of first-dose vaccinations to more than 31 million.

Explaining herd immunity, Prof Friston said "more people than you might imagine have been exposed to the virus" in the UK.

He said the virus had nowhere to go with more than 50 per cent of adults inoculated against Covid-19, a further 42 per cent with antibodies through previous infection and 10 per cent thought to have innate immunity. About 70 per cent of the population is immune when combined with the estimated efficacy of vaccines.

"Achieving herd immunity means the virus is on the path to dying out," he said.

"It's certainly a milestone in moving from an epidemic to an endemic phase, but it doesn't mean we should suddenly unlock. If we now suddenly increase contact rates through premature unlocking then the R ratio would jump above 1, the herd immunity threshold would increase and we would no longer be in a safe situation."

The herd immunity threshold is heavily influenced by the R number - how fast the virus spreads - which rises and falls based on community transmission of the virus.

Prof Friston said the threshold could go down in summer as people mix outdoors but there is a chance it may increase if new variants of the virus take hold.

Oxford Vaccine Group: Not the time to waver

The encouraging findings come as UK regulators on Wednesday announced people under 30 will be offered an alternative vaccine to the one developed by AstraZeneca over concerns about rare blood clots.

The Medicines and Healthcare Products Regulatory Agency said the clots were “extremely rare”, but a risk/benefit analysis meant it was preferable for young people to receive alternative shots.

We need to put our confidence in the hands of the system

Matt Hancock

The announcement was designed to maintain public confidence in the vaccine after weeks of debate in Europe over the safety of the medication.

Mr Hancock reassured the public that the risk of blood clots was rare and the safety monitoring system was working.

“The safety system that we have around this vaccine is so sensitive that it can pick up events that are four in a million,” he said.

“I’m told this is about the equivalent risk of taking a long-haul flight.”

Oxford Vaccine Group director Prof Andrew Pollard said now was not the time to waver.

“We need to put our confidence in the hands of the system,” he said.

“These are such rare events that even in the 60,000 people who have taken part in trials there were no cases. It is almost impossible until you get to this large scale to identify this possible link.”

Updated: April 8, 2021 07:32 PM

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