John Edmunds has been at the centre of the unravelling of the Covid-19
pandemic since cases first appeared in January 2020. A member of Sage, the
government’s scientific advisory group, and a professor of epidemiology at
the London School of Hygiene & Tropical Medicine, he has consistently
warned ministers about the threats posed by the disease.

These risks have often been clear in their nature. But today, 18 months
after Covid-19 first appeared, he believes the nation stands at a point of
maximum uncertainty about the future of the pandemic.

https://www.theguardian.com/world/2021/aug/01/is-covid-19-on-the-run-in-the-uk-fall-case-numbers-herd-immunity

“At any other point of the epidemic, it has been easier to foresee what
might happen,” he told the Observer. “But at this point, I think it’s
really hard to understand what has happened and what is going to happen in
the long term. There is a huge amount of uncertainty about the disease at
the moment.”

The fact that we are a year and a half into the pandemic and are still
being wrongfooted by Covid-19 may seem surprising. After all, in that
time, we have developed powerful vaccines to protect against it and have
pinpointed critically important drugs to treat patients. Science has
worked wonders.

Nevertheless, researchers are still very unsure about how Covid-19 will
progress in the UK in the coming months.

The statistics have certainly been startling. First, case numbers rocketed
at the beginning of July. Then they reversed and began to fall, leaving
statisticians and scientists struggling to make sense of the fluctuating
figures. For good measure, a host of conflicting factors has been put
forward to explain Covid case numbers.

Has the opening up of society on 19 July had a major impact? Did Euro 2020
propel the virus through the homes and pubs of England? Could the UK be
approaching herd immunity? And what impact have the school holidays had on
the progress of the disease?

Untangling these factors, as well as understanding the exact impact
vaccines have had on society, has now become a complex, urgent business.
“It will tell us just how bad things are likely to get when society really
opens up in September and October and as winter approaches,” said Edmunds.

There is clear agreement on one factor, however. All the evidence
indicates that vaccines are now playing a pivotal role in controlling the
disease. Had the government completely opened society on an unprotected
populace, daily death tolls would by now have soared into their thousands.
But just how far has our vaccine protection reached?

It is a crucial question, whose answer will determine just how severe will
be the return of Covid-19 in the autumn as schools reopen, the weather
chills and people head indoors. A key factor is the degree to which the
country has achieved herd immunity. In other words, will we have reached
the point where so many people have been either infected or vaccinated –
and therefore possess some immunity to the disease – that viral
transmission falls or even stops?

“You can run some very simple models to see if the case numbers that we
saw earlier this month are consistent with effective herd immunity,” said
Prof Mark Woolhouse of Edinburgh University. “And in my view the answer
is, yes, it is. There are some big caveats but the bottom line is that
those figures are consistent with the impact of herd immunity.”

Woolhouse pointed to a recent Office of National Statistics survey which
showed that around 90% of adults in the UK now possessed Covid antibodies,
which indicates that they could be capable of some kind of immune response
to infection. “That is a very large fraction and it may well be having an
impact,” he said.

Prof Martin Hibberd, also of the London School of Hygiene and Tropical
Medicine, agreed that herd immunity was becoming a realistic prospect. “We
are approaching herd immunity but I don’t think we’re quite there yet,” he
said.

But if we are nearing this sought-after goal, why was there such a rapid
rise in cases in mid-July? What circumstances could have triggered this
massive leap in infections in a nation that is supposed to be heading
towards herd immunity? Scientists point to two key factors: the Euros and
schools closing for the holidays.

“If you look at herd immunity, you would expect it to peak at different
times in different parts of the country as there are differing levels of
immunity across the country,” said Edmunds. “But this is not what we saw:
we saw a synchronous drop in cases right across England. This suggests an
external factor was behind it – something that occurred across the country
at the same time.”

And the two most likely candidates, he said, are schools closing and the
“pingdemic” that occurred immediately after the Euros. In other words, the
large gatherings of fans – mostly male – in pubs to watch England play
football would have triggered jumps in case numbers in mid-July. This
would have been followed by a rise in contacts being asked to self-isolate
after being linked to infected fans.

“This bout of self-isolation occurred across the country at the same time,
and it looks like it reduced cases,” Edmunds said. “But these would be
expected to go up again – if were not for the effect of school closures.

“Pupils are no longer bringing home viruses after picking them up in
class. This is now probably helping to hold cases down, and may well do so
over the summer.”

This point was backed by Woolhouse. “We are now three and a half weeks
past our peak in Scotland, and numbers are still not going back up. So,
you know, I’m more confident that the underlying trend is in the right
direction.”

Prof James Naismith, director of the Rosalind Franklin Institute in
Oxford, also thinks the short-term picture is optimistic. “It looks as if
case numbers are plateauing, and one would hope they will drop somewhat
over summer,” he said.

However, problems will return in September when children go back to
school, businesses open up and people spend more time indoors.

“We will still have high levels of infection in the community. About one
person in 65 carries the virus at present, and that means virus levels are
not going to go down significantly by September,” Naismith said. “Under
those circumstances, the virus will have a good platform from which to
start infecting those who are unprotected when conditions make it more
favourable for it to spread.”

This point was backed by virologist Stephen Griffin of Leeds University.
“I am worried that even if case numbers continue to go down, they will
start to come back up again with a vengeance in September when the schools
go back.”

One solution proposed by Naismith is to vaccinate 16- and 17-year-olds
across the UK. That would protect them from Covid-19 complications, which
are worse than any vaccine complications they might encounter. It would
also push the population closer to the level it needs to achieve herd
immunity.

“I think we are close to that immunity but will not be quite there by
autumn,” he added. “So we should be thinking about whether or not to
vaccinate 16- and 17-year-olds. That would help us achieve wider
protection against the virus. In any case, teenagers are perfectly capable
of making up their own minds about the risks and benefits involved in
being vaccinated. After all, 16-year-olds in Scotland are allowed to vote.”

Two further vexing issues bedevil attempts to clarify the nation’s route
out of the pandemic: new variants and possible fading vaccine efficacy.
The danger posed by new variants concern is raised by Jeremy Farrar,
director of the Wellcome Trust, in Spike: The Virus v the People, his new
book about the pandemic. High infection rates raise the chances of a new
variant being cooked up, he argues. “That is very probably why the
variants of concern have been traced to countries like the UK, South
Africa and Brazil, which have had poorly controlled transmission.”

These fears are echoed by Hibberd. “It is possible that, with luck, the
virus will not be able to mutate sufficiently to enable it to escape the
immunity being provided by vaccines or previous infections,” he told the
Observer. “Nevertheless, the appearance of an immunity-evading virus is a
distinct possibility. After all, it happens with other viruses, like
influenza. We have to create new vaccines against flu every year, and it
mutates and comes back the next year slightly changed, and we then have to
develop a new vaccine to tackle it.”

At present, scientists and pharmaceutical companies are working on
vaccines to tackle some of the new variants that have appeared over the
past year. For example, the Oxford vaccine team led by Dame Sarah Gilbert
is working on one for the beta variant, first discovered in South Africa,
which is considered to be the one with the greatest potential to evade
vaccines.

And then there is the issue of vaccine efficacy. Studies have shown that
Covid-19 antibodies decrease over time in vaccinated individuals. This may
limit people’s protection against the virus.