Some think the covid-19 pandemic is over 鈥� but it most certainly isn鈥檛. On the contrary, around the world, the number of confirmed cases is rising rapidly again. The most concerning situation is in China, where many older people still have no immune protection of any kind and which is currently battling a major outbreak. So why are cases on the聽rise again, how bad will it be聽and what could happen next?
The omicron variant that first started spreading in November 2021 caused by far the biggest wave of the pandemic to date. Globally, reported covid-19 cases peaked towards the end of January this year, and they were falling nearly as fast as they shot up. But now they have begun to rise sharply again, according to the World Health Organization (WHO).
Because many countries are doing less testing than they did at the peak of the omicron wave, the actual increase could be even bigger than this, said WHO director-general Tedros Adhanom Ghebreyesus during a briefing on 16 March. Deaths are still declining globally, but they are expected to rise again too; deaths usually lag cases by around three weeks.
Advertisement
The situation isn鈥檛 the same everywhere. In some nations that聽had big omicron waves, the number of reported cases is still falling. Notably, that includes South Africa, the first country to聽have an omicron wave.
The number of tests being done in South Africa has fallen sharply, . But the proportion of positive tests has fallen from 37 per cent to 7 per cent over this period, which indicates that case numbers really are falling.
In other parts of Africa, Europe and Asia, reported cases have begun to climb again. Some countries that had big omicron waves, including the UK, Germany and France, are seeing a resurgence before the previous wave has even subsided.
Breakdowns of case numbers by which virus variant is responsible show that while聽the initial wave of聽omicron was mainly caused by one of its subvariants called BA.1, the 叠础.2听蝉耻产惫补谤颈补苍迟 is driving the resurgence. The term omicron refers to a whole family of related variants that appeared around the聽same time, rather than to one聽specific variant. BA.2 has been around from the start and is even better at spreading than BA.1.
鈥淭his is the most transmissible variant we have seen of the SARS-CoV-2 virus to date,鈥� said at the WHO during the briefing on 16 March. A study in Denmark , but this is rare and may not be a major element in the overlapping waves.
BA.2 isn鈥檛 the only factor involved. 鈥淲e鈥檝e dropped all measures, so a resurgence is not very surprising,鈥� says at the University of Oxford, referring to the situation in England.
鈥淟ifting of the use of masks, lifting of physical distancing, lifting of restrictions limiting people鈥檚 movement, this provides the virus an opportunity to spread,鈥� said Van Kerkhove.
In contrast to some countries in聽Europe, South Africa has been maintaining measures, such as mask wearing in public spaces, and this might be helping to limit聽the BA.2 wave there. BA.2 has聽become the dominant variant, but it hasn鈥檛 caused enough cases to increase overall case numbers.
But there is no way to be sure that maintaining measures is why the BA.2 wave is smaller in South Africa, says Katzourakis. The nation also differs from European countries in other ways, he says 鈥� for instance, most people there have acquired immunity from infection rather than vaccination.
People may also be taking fewer聽precautions because of the misperception that the pandemic is over and that omicron is mild, said Van Kerkhove. Omicron is in those infected than the delta variant. But because it is more transmissible, in the omicron wave than during the delta wave 鈥� there聽have been more than 150,000聽deaths in聽the US since聽December 2021.
A third factor that some experts have suggested is involved is the waning of immunity. However, in聽England, different age groups were vaccinated at different times, but cases in the latest wave began rising in all age groups at the same time. This suggests that waning immunity isn鈥檛 a major factor.
How bad will it get?
The severity of this second wave of omicron, in terms of deaths and hospitalisations, will depend mainly on vaccination rates. For instance, Australia reported twice as many cases during its omicron wave as the US, but despite people having no prior immunity from past infection, it had half the death rate. Around 82 per cent of people in Australia are fully vaccinated compared with 65 per cent in the US.
The situation in Hong Kong shows just how bad things can get聽when the BA.2 variant starts spreading in a population with little immune protection. Because Hong Kong鈥檚 zero-covid policy had聽previously been effective, people there had no immunity from infection before the omicron wave, and only聽30聽per cent of those over 80 had been fully vaccinated. When omicron started spreading widely in February, many older people became severely ill, overwhelming hospitals and causing deaths to skyrocket.
The big question now is whether something similar could聽happen in mainland China, where vaccination rates are also聽low in older people, and which is struggling to contain its聽biggest outbreak since the pandemic first began in Wuhan. Tens of millions of people have been put under lockdowns since聽the start of March.
鈥淚f they do fail to continue to suppress the virus, they鈥檙e in big, big trouble,鈥� says Katzourakis. 鈥淚t would be a humanitarian catastrophe.鈥� While nearly 90 per cent of China鈥檚 population is vaccinated, only 51 per cent of people over 80 have had two shots and just 20 per cent of this group have had a booster, said health officials in Beijing .
鈥淭he outbreak in Hong Kong is a particularly profound lesson for us, an example that if the vaccination rate for the elderly is low, the rate of severe cases and deaths will be high,鈥� said at the National Health Commission in China.
What鈥檚 more, China has been vaccinating people with locally made vaccines that are used in many other countries. However, it appears that at least one of these聽鈥� the CoronaVac vaccine made by China-based firm Sinovac聽鈥� does still give fairly high protection against severe disease.
If China rapidly vaccinates far more of its oldest people, it should be able to avoid a repeat of Hong Kong even if it fails to suppress the virus, says at the University of Hong Kong, who has studied the effectiveness of the CoronaVac and BioNTech/Pfizer vaccines used there.
He found that in people over 60,聽neither vaccine provided any protection against infection by omicron, but that two doses of CoronaVac are 65聽per cent effective against severe disease, rising to 96聽per cent with a booster. For聽Pfizer, it is 86聽per cent and聽97聽per cent respectively.
What is certain is that this latest wave of coronavirus cases will subside, as all the other waves have done. Even if no other new variants evolved, there could still聽be a series of future waves of聽omicron as immunity wanes.
But there definitely will be new聽variants. In fact, researchers recently found a recombinant coronavirus with genetic material from both the omicron and delta lineages that arose when someone was infected by both at once. This 鈥淴D鈥� recombinant isn鈥檛 expected to be a major problem because it looks like omicron to the immune system, but recombination could create more problematic variants.
There is no guarantee that future variants will be less dangerous, says Katzourakis. It was a coincidence that omicron was less likely to cause severe disease in those infected, he says.
What鈥檚 more, omicron not only聽largely evaded people鈥檚 immune protection against infection, it also slightly evaded their immune protection against severe disease. As future variants evolve in a world where most people have immunity, we could see the rapid evolution of聽variants that easily evade protection against severe disease.
鈥淭he next omicron may take less time to arrive than omicron itself,鈥� says Katzourakis. 鈥淭he hope is that this time is long enough that we can up our game in terms of vaccines and therapeutics.鈥�
鈥淭hat鈥檚 the optimistic scenario,鈥� he says. 鈥淭he pessimistic one is that we give up on developing and deploying vaccines now that we think it鈥檚 all over, and a variant comes along in a year鈥檚 time that we鈥檙e totally unprepared to deal with.鈥�
Sign up to our free Health Check newsletter for a round-up of all the health and fitness news you need to know, every Saturday
