Why did China relax its Covid policy - and should we be worried?

After long pursing a zero-Covid policy, China has relaxed many restrictions including quarantine rules for travellers. But some experts have raised concerns the U-turn may cause problems. We take a look at why.

Until recently China followed a zero-Covid policy, including strict lockdowns and quarantining those testing positive and their close contacts. However, earlier this month China made an abrupt U-turn, abandoning many - although not all- of its restrictions, apparently in response to protests.

Among the measures it has scrapped is the use of its primary Covid tracking app, and domestic travel restrictions have been lifted. The government has allowed people with Covid to quarantine at home and said that from early January overseas visitors entering the country will no longer have to go into quarantine.

China is experiencing a large wave of Covid infections, with reports of hospitals under intense pressure. However, it is hard to know how many deaths have occurred: last week China changed the definition of Covid deaths so that only patients with the virus who die because of pneumonia and respiratory failure now meet the criteria.

There are a number of reasons. The relaxation of restrictions has given the virus a greater chance to spread, and China's sluggish vaccination campaign, coupled with the use of a less effective vaccine than those developed in the west, means the population has little protection and many vulnerable people remain at risk from the virus.

In addition, the tight restrictions previously employed mean few people have had Covid before. That means there is little natural immunity at play in the current wave.

As a result of all this, many people are now getting Covid at the same time, and needing hospital care, leading to mounting pressure on healthcare systems.

Some have welcomed the shift away from a zero-Covid policy, pointing to the economic and social harms of the continued approach. Many countries that initially pursued such policies, including New Zealand and South Korea, loosened their restrictions much earlier. The difference is that these countries did so gradually, and have made use of safe and effective vaccines and treatments, offering protection from the worst outcomes.

"The sudden shift in policy is certainly concerning for China - the fact that very few people have had Covid, plus a lower uptake of vaccines/boosters, [especially] in vulnerable age groups, means that they have lower overall immunity, particularly in the vulnerable, than the rest of the world right now," said Dr Emma Hodcroft, a molecular epidemiologist at the University of Bern and the University of Geneva in Switzerland.

Another concern centres on the transparency - or lack thereof - around the impact of the current wave in China, and changes in the genetics of the virus.

"The infection rates in China are very high at the moment - and with uncertainty about what variants are actually circulating there, and the extent of infection, there is a lot we don't know," said Prof Rowland Kao of the University of Edinburgh.

Some countries have already put in place extra travel requirements, such as testing or quarantining, for visitors from China.

Experts have argued such restrictions will make little difference to the number of new cases in countries where Covid infection levels are already high. However, if positive samples from such testing are sequenced, the approach could shed light on the variants at play in China.

But experts have warned that the use of border restrictions to keep out new variants has not previously worked well when only applied to particular countries. "Where border closures have had an impact they have applied to almost all arrivals," said Prof Mark Woolhouse of the University of Edinburgh.

Prof Tom Wenseleers, an evolutionary biologist at the Catholic University of Leuven in Belgium, said while better genetic surveillance was important, he was not particularly concerned about the possibility of new variants emerging in China, given that the main driver for changes to the virus is the shift in the immune landscape resulting from exposure to different naturally circulating variants and vaccination.

"The required standing genetic variation that would allow new variants to pop up is there anyway, in patients with chronic infections throughout the world," he said.

Indeed, new variants can, and have, cropped up in myriad countries, while Covid currently has high circulation around the world.

Hodcroft also stressed that most recent variants to appear have adapted to dodge immunity. "In China however, since the level of immunity is quite low, we don't expect there to be much pressure on the virus to evolve around it - it simply doesn't have to," she said. "Thus, I am not expecting there's much evolutionary pressure that would mean seeing new variants out of China, at least not ones that pose a threat to the rest of us."