Expert answers to eight of your urgent questions on falling Covid infection numbers

With Covid infections continuing to decrease across the UK, scientists and government experts have offered a number of theories to explain this downward trend, ranging from herd immunity to the effects of the recent warm weather.

There are no clear answers, for now at least, but the falling rates are a clear sign that the UK has past the peak of its predicted ‘exit wave’.

As part of an ‘Ask Me Anything’ session, science correspondent Samuel Lovett and Covid expert Colin Angus, of Sheffield University, were one hand to answer your questions.

As we head towards 90% of our over 18 having been double jabbed, will we be able to move away from being so concentrated on cases? Thank you (Becka49)

Samuel Lovett: Personally, I think it’d be a wise idea to move away from the focus on infections, and instead keep an eye on the rate of hospitalisations across the UK. This will be the real determinant of whether or not restrictions need to be reimposed in the months ahead, so as to give the NHS some breathing space if it heats up too much.

I don’t know when the right time will be to make that transition - it could be when the government and its advisers are confident that we’re through the worst of our epidemic (they reckon we’ll be fully back to normal by next spring). We definitely need to keep an eye out for what happens over the winter, but, for now, I’d take comfort from the fact we’re moving in the direction.

Falling infection rates could easily be linked to decreasing testing. When will “increased contact due to bars and pubs reopening and nobody wearing masks anymore” start to show up as infection rates increasing? Two weeks from “freedom day” or more? (TheatreFan)

Colin Angus: Test positivity has also fallen sharply as cases have started falling, so it is *extremely* unlikely that the recent collapse in case numbers is just down to a reduction in testing, or even that that is a major contributor to the fall we’ve seen.

But, we would only expect to see the impacts of any change in behaviour after July 19th feeding through into the case data in the next few days, so we will have to wait and see. The early signs seem to suggest that the fall in cases has levelled off in younger ages, but continued in older ones. It’s certainly too early to break out the champagne and declare this wave over, but it’s looking fairly hopeful at the moment.

Will the 3rd -’Booster’ vaccinations in the Autumn be based on the original strains spike-or on the Delta-? Or a mixture of spikes? And would a vaccination with a different shaped spike protein WORK as a booster for the similarly shaped original SARS2 Coronavirus from 2019? (Terence)

SL: As far as we know, the autumn booster programme will use vaccines that have been already licensed in the UK, instead of the jabs that are currently being developed to target the different coronavirus variants. Although we know efficacy is diminished against some of the different variants (like Delta and Beta), they remain effective in ‘topping up’ immunity and providing protection against serious disease/death.

For your second question, the original Wuhan version of the virus is no longer in circulation as it’s been outcompeted by the more transmissible variants out there. So this isn’t something we need to worry about.

Is it the case that a combination of factors such as, higher temperatures, immunity rates, and the ‘Pingdemic’ have all contributed to falling rates of Covid-19? It may be too soon to say, but is there any data to suggest how much each of these factors affect the infection rates? (AndyF35)

CA: I’m generally pretty cautious about attaching explanations to the patterns we see in Covid case data, but I think we can be relatively confident that two big factors in the recent fall in cases in England are the end of Euro2020 and schools breaking up. One reason we can be confident about this is that Scotland experienced both several weeks before England (or at least, the end of Scottish involvement in the Euros!) and cases started to fall shortly thereafter. Of course, other factors, like vaccination rates, the weather etc. are also likely to play a role, but I think these are less likely to be responsible for the very dramatic drop in case numbers we’ve seen.

We will get a better idea of how these various factors have played into case numbers as time goes on - particularly when schools and universities go back in September - but explaining everything fully is *hard*. If there’s one thing that the last 18 months have taught me, it’s that we need to be humble about how much we really understand about Covid (and human behaviour!). Fundamentally, predicting or explaining the behaviour of a highly infectious disease is always going to be difficult. But we’ll keep looking at the numbers and trying to work out as best we can what might be going on.

I saw your report from earlier that the UK had developed a SARS plan in 2005 which could have been used in the context of Covid-19 when it first emerged. Do you think it’s likely it would have made a difference had the government been aware of it? (EMcD)

SL: Yes, I definitely think it would have made a difference. From those I’ve spoken with, it would have seen the UK start its preparations far earlier - as far back as late January - and helped put us on the front foot against Covid-19. It certainly wouldn’t have stopped the progression of an epidemic here, I don’t think, but I’m confident it would have softened the initial blow. I talk more about this is in an analysis I wrote earlier. Feel free to give it a read here.