Infections are falling but may rise again – will high vaccination rates be enough?
The UK has been through two large waves of COVID-19 and is currently in the middle of a third.
Yet despite cases being high, both scientists and politicians are cautiously optimistic that the worst of the pandemic is behind the UK. At the same time, it needs to be recognised that the pandemic is likely not over.
The UK’s second wave, last winter, was fuelled by the alpha variant of the coronavirus. The current wave, instead, is being driven by the delta variant, which is more transmissible and has some ability to get around the vaccine protection.
Despite this, vaccination has meant that the dynamics of these waves have differed substantially. The most recent wave has spread primarily among the young, with older people largely protected by vaccines. Because young people are generally less vulnerable to COVID-19, deaths and hospitalisations have been much lower this summer compared to January, despite a similar number of cases.
And after rising in June and July, cases, hospital admissions and deaths in the UK have dropped from their peak, although it is unclear that they will keep falling and cases may even be rising again. It’s not completely understood why this fall has happened, though in my view, herd immunity is unlikely to be the cause. Israel, which has similarly high levels of vaccination, is seeing cases continually rise.
Most likely, falling infections in Britain have been caused by a combination of the end of the Euro 2020 football tournament (which temporarily raised rates of mixing between people during June and July) and the beginning of school holidays (which has reduced mixing among young, unvaccinated people). The UK’s test-and-trace programme also resulted in many people self-isolating recently when cases were at their highest, which will have reduced mixing.
What will happen next?
So far, the UK has vaccinated 89% of its adult population with a first vaccine dose and 76% with a second, meaning that around 59% of the total population is fully vaccinated. This places the country among the world leaders when it comes to vaccine coverage. With the UK soon to roll out COVID-19 vaccines universally to 16- and 17-year-olds, overall coverage will continue to increase.
Yet even such high levels are far from enough to allow a complete return to pre-lockdown activity without starting new outbreaks. Although the exact threshold is strongly disputed, herd immunity is unlikely to be reached unless vaccination is extended to young children, if it can be reached at all.
Still, in combination with other control measures, current rates of vaccination might now be enough to protect the British health system from collapse should another big wave appear. Vaccination with two doses is between 65% and 90% effective at preventing symptomatic delta infections. The effectiveness is even higher for protection against hospitalisation or deaths.
But while the mass vaccination strategy is clearly paying off by blunting the impact of delta’s spread, significant pockets of the population remain vulnerable. They include adults who are still unvaccinated – of which there are over 5 million – and young school children.
And controversially, over the past month the majority of the UK’s COVID-19 restrictions have eased. Sport and entertainment venues reopening are likely to fuel further outbreaks, as will children returning to school at the end of summer.
In the short term, almost all recent modelling scenarios predict another significant outbreak in late summer, despite the country’s good vaccination coverage. However, there’s high uncertainty among those creating the government’s models about how exactly a future spike will manifest itself.
Medium term, loss of immunity over time and the rise of new COVID-19 variants may ignite new outbreaks – and consequently higher levels of death – among older people. Booster doses are therefore being considered for the vulnerable. This is controversial, going against calls from the World Health Organization for rich countries to prioritise donating vaccine doses to countries in need.
Long term, the situation is even less certain. The most likely scenario is that the virus will become endemic in the UK, re-emerging particularly in winter when people mix more indoors.
How effective has the UK’s response been?
Since the beginning of the pandemic, the UK government has consistently delayed implementing restrictions and relaxed them while cases are still relatively high, with a reluctance to close borders. Restrictions have therefore needed to be repeatedly reintroduced, with the country put into lockdown three times.
This strategy resulted in a relatively high COVID-19 death rate. It also saw a high drop in GDP in 2020 as compared to 2019, with the construction and manufacturing industries affected most. These sectors tend to be concentrated in areas of higher deprivation, such as the West Midlands or north-east of England. So low-paid workers have borne a double burden, as people in more deprived areas are also more likely to have experienced worse health outcomes from COVID-19.
Given the past losses, the government is understandably keen to reopen the economy, including the services and entertainment industries. It also knows it is important to get school pupils and university students back into learning so far as is possible.
There are, though, risks with letting the virus spread in the young population, including the threat of long COVID. Chains of transmission are now limited due to holidays, but the return to school in Scotland from August 17 will be closely scrutinised.
The decision to lift the majority of control measures this summer, with cases lower than they have been but still relatively high, shows that the government accepts that some people will still get the virus and that a small number will possibly die. However, investment in vaccines and their impressive rollout have led to a situation where future outbreaks – and they will come – might be self-limiting without the need of further country-wide lockdowns. Other countries will be watching closely to see how the situation evolves.
Adam Kleczkowski, professor of mathematics and statistics, University of Strathclyde
This article is republished from The Conversation under a Creative Commons license. Read the original article.
