Why are Covid cases dropping in the UK?

As July 19th, “Freedom Day”, approached and the UK dropped the legal requirements for many of the measures that had been implemented to control Covid-19, there were expressions of alarm from around the world. Over 100 scientists signed a letter to the Lancet medical journal stating, “the Government is embarking on a dangerous and unethical experiment, and we call on it to pause plans to abandon mitigation.” The WHO’s Mike Ryan said, “The idea that everyone is protected and it’s ‘kum-ba-ya’ and it can go back to normal, is a very dangerous assumption.” And Imperial College’s Professor Neil Ferguson, dubbed by one newspaper as “Pandemic Prognosticator in Chief”, declared, “I think 100,000 cases a day, it’s almost inevitable.” But cases now sit at a quarter of that, and have fallen to less than half of where they peaked, in mid-July, at 60,000 daily cases. Whether this decline will continue is, as yet, uncertain, and there are signs they will probably rise again as “normality” returns, but what’s behind this viral volte-face? Chris Smith asked Warwick University virologist Lawrence Young whether the outcome was one he’d expected, and how he now sees us managing the pandemic as we go forward…

Lawrence - I'm quite surprised by the very steep drop in numbers happening so quickly. It's obviously a combination of a number of different factors - recent hot weather in the UK does help, that promotes people to go outside a bit more in well ventilated, external spaces where the virus doesn't spread as much. The virus doesn't like the sun. We've got really good levels of vaccine uptake. And I think also people are behaving themselves. So even though all the restrictions were lifted in England on the 19th of July, I've seen many people still wearing face masks in indoor areas and just being a little bit cautious, and I'm sure all of that has contributed.

Chris - It's very stark, the contrast with what people were saying in the press though. I mean, you've got the WHO "this is morally reprehensible". You've got very significant political, prominent figures internationally saying that this is a dangerous experiment what the UK did. What do you think they're saying now?

Lawrence - Yeah, I think they're all looking at us as a big experiment really. None of us know how this virus is going to behave, this is uncharted territory for all of us. And whilst many of us, myself included, were really concerned about the lifting of all restrictions in England on the 19th of July, and we have yet to see the impact of that on case numbers, it's quite clear that we've reached some sort of turning point and we just need to keep an eye on numbers. A number of factors also need to be taken into account like how many people are actually being tested at the moment. The numbers do look like they've gone down by about 14% over the last week or so, so there are other factors that might impact this.

Chris - We have been obviously prioritising vaccination for higher risk groups, older people, people judged to be extremely clinically vulnerable. We've worked our way down the age bracket. And the consequence of that was most of the cases that we were seeing were among the young vaccinated, and particularly therefore younger people. Now, given that the numbers did go up quite a lot and then suddenly started to come down and they've come down a lot, does this mean perhaps, as one commentator put it last week, that the virus is just running out of people to infect?

Lawrence - That certainly could be the case. If you look at the number of individuals with antibodies and the impact of certain behavioural changes too. I mean, one of the factors that people have discussed is the football and the impact of the Euros and the way that clearly, perhaps younger people in particular, were more likely to be in crowded spaces, in bars, et cetera, during the football, and that would have had a bounce effect on the numbers and now that's come out obviously. But I still think we need to keep an eye on the 18 to 30-year-olds. We know that that population is still unvaccinated, at least perhaps 30% of that population. If we look at what's happened in other countries, like the Netherlands, it's in that group that the virus has spread and caused the country to impose further restrictions.

Chris - One thing that's got some people confused though is that when we vaccinate against things like measles, we're comfortable that you're probably going to have immunity for life. Whereas we're seeing this situation with these coronaviruses where double jabbed people are still catching it. So it's not really immunity. So what's actually going on?

Lawrence - I think this is a really interesting issue. People are still working on this whole idea of 'how long does the immune response persist for', in individuals who are double vaccinated we're seeing breakthrough infection. And that's why, again, there's this big discussion going on about whether we should be boosting the elderly and most vulnerable over the winter months just to give that additional protective cover to the most vulnerable. And part of this is also understanding how the body's immune response works and whether or not actually, in the future, we might be able to tweak or modify coronavirus vaccines so that we do get long-lived protective immunity.

Chris - It's quite analogous to flu isn't it because probably many more people catch the flu, but they don't realise it because they've got some semblance of immunity from previous infections that means that their severity of illness is mitigated greatly. So are we marching into a sort of regime where coronavirus is probably going to be similar, where we've got background levels of immunity in the population and when people do catch it, they catch it trivially rather than potentially lethally as they would once have done?

Lawrence - That, I guess, is the hope actually. And if you look at the common cold coronaviruses, the viruses that have been in circulation for many, many, many years in human populations, these just cause very low-level infections. And our bodies, particularly youngsters, get reinfected with common cold coronaviruses - their immune systems are getting tweaked all the while. I think the interesting thing is, as we're dealing with virus variants of this coronavirus, to what degree can the current vaccines actually provide appropriate cover for variants that exist and perhaps variants that will crop up in the future? Or are we going to have to live in this cycle of having to tweak vaccines every year, as we do with flu, to cover the predominant new variant of this coronavirus?

Chris - And what do you think?

Lawrence - I think things will settle down after a while. Actually, it might take a year or two, but I think we'll settle down into some form of what we call endemic infection, where the virus is a bit like flu. It may be that we want to continue to vaccinate the elderly and the most vulnerable. But I think some really exciting developments have come alongside this pandemic in terms of vaccine generation. And there's really exciting new work coming out suggesting that it might be possible to develop something called a pancoronavirus vaccine, a vaccine that's going to cover all types of coronavirus, including those that don't currently exist or haven't spilled over into the human population. So I think one of the positives, if there dare I say there is any positive out of the pandemic, is this hastened approach and this new approach to thinking more creatively about vaccines for future outbreaks of virus infection.