In the United States, the number of Covid-19 cases has been declining since January. They may have plateaued as a sub-variant of Omicron, BA.2, becomes a major cause of infections.
But in China, a region of the world that saw few spikes during the pandemic, there has been a sharp increase in cases as BA.2 spreads across the country.
The difference, experts say, lies partly in policy and partly in immunity at the population level. What happens in China does not necessarily mean that the US is in for another huge spike in cases.
“Public health is a very local thing,” said Andy Pekosh, a virologist at the Johns Hopkins School of Public Health.
With the first cases of Covid-19 in 2020, the trends around the world were similar, he said, because most people’s bodies had no experience with the coronavirus and there were no vaccines. They had no defense against him.
Since then, different countries have used different vaccines and have had varying degrees of success with vaccination campaigns. There are also different levels of immunity among the population in different regions. All of this affects the trajectory of Covid-19 cases.
“You probably expect to see more country-to-country variation in terms of case numbers, spikes and death rates,” Pekosh said. “All of this means that it’s just hard to make unambiguous statements about how things will play out.”
Various business strategies
Quarantines in the US are a thing of the past and likely to remain so, public health experts say. While the decline in U.S. cases appears to be leveling off, it’s rare to see someone wearing a mask in many places.
If someone tests positive for Covid-19 – even if they don’t have symptoms – they must be isolated in large temporary facilities set up in stadiums and convention centers. They cannot leave until they have tested negative twice. Pets are even sent to other centers for observation. Public health officials cordoned off the man’s home and disinfected everything.
With the highly contagious Omicron variant, lockdowns may not completely stop the rise in cases, experts say, but this strategy has helped.
“It’s a stark contrast,” said Abram Wagner, an assistant professor of epidemiology at the University of Michigan. “We are on different trajectories: the number of cases in the US is declining and is currently on a plateau, so the direction is different. But I think seeing fewer cases in China, I think China’s policy of playing with restrictions on some level has had an effect.”
According to him, whether strict restrictions are too arbitrary and infringe on personal freedoms too much. But in China, the number of cases was generally much lower than in the US, even during the surge.
What made things more difficult is how easy it is to get Covid with Omicron.
“Omicron has made a difference in China,” Wagner said. “It’s just hard to maintain a dynamic zero Covid policy that will completely eradicate it.”
“Their firewall broke because of Omicron”
“Omicron, when compared to other options before it, really changed the playing field a lot,” Pekosh said. “His transmissibility is just off the charts.”
Omicron’s chance of spreading is three times higher than the Delta variant. None of the vaccines made to protect against the original strain are working, especially in the Chinese population, which hasn’t had a spike in the past two years.
“In a way, their firewall broke because of Omicron, and they have a huge number of people susceptible to this virus,” said Justin Lessler, an epidemiologist at the School of Global Public Health. Gillings University of North Carolina.
BA.2, which has played a role in the surge in cases in China and is currently the dominant strain in the US, is particularly contagious. Some epidemiologists say that the base reproduction number of BA.2 can be as high as 12, meaning that each sick person can infect an average of 12 others. This puts it on a par with measles.
While it is difficult to predict the trajectory of a pandemic in the US, public immunity could keep the country from a widespread resurgence, Lessler said. Instead, we should see a “soft flash”.
“I expect to see some resurgence here, but it’s a very different picture, even with the increase in the Omicron BA.2 sub-variant,” Lessler said.
The US population has developed an immunity that China does not have. China has seen relatively few cases during the pandemic, but the U.S. Centers for Disease Control and Prevention estimates that 37 million Americans — about 1 in 11 — contracted Covid-19 just last winter.
” [BA.2] The Omicron sub-variant is not a complete leap forward from Omicron, while Omicron was indeed very different from Delta,” said Dr. Davidson Hammer, professor of global health and medicine at Boston University. “I think there are a lot of people, at least the United States, who have had Omicron and there is growing evidence that they are close enough in terms of their immunological profile that if you have had 1 you are unlikely to get 2″.
In other words, the number of people who can get infected in the US is more limited than in China.
Differences in vaccination strategies
Another concern for China could be the type of vaccines it uses, said Dr. Ian Lipkin, professor of epidemiology at Columbia University’s Mailman School of Public Health.
“The increase in cases reflects a combination of factors. Your population, immunologically naive, they haven’t seen much of the virus in the past and because they haven’t been effectively vaccinated to counter it,” Likpkin said.
Other studies have shown that immunity from two doses of these vaccines wanes rapidly and that protection may be limited, especially among the elderly and especially when compared to the mRNA vaccines used in the US. All vaccines have been found to provide less protection against Omicron.
Wagner thinks the difference between US and Chinese vaccines can be rather superficial when it comes to Omicron, but Lipkin says he’s been telling his colleagues in China for months that they need better protection.
“The way out of the surge could be to quickly vaccinate everyone with more effective vaccines. That’s not what they do,” Lipkin said. “The notion that you can somehow beat this with lockdowns doesn’t work if you don’t combine lockdown with an effective vaccination strategy.
“It’s so discouraging and disturbing,” he added. “I spend a huge amount of time in China and have been advising them for months to change the vaccine, but they just don’t want to do it.”
It matters who is vaccinated
“My understanding is that vaccination rates are somewhat inverted in China and older people have lower vaccination rates,” he said.
In the US this week, the Biden administration expanded second booster eligibility to people aged 50 and over, but one element that could limit that strategy is money. Congress failed to pass legislation that would fund Covid efforts. The uninsured may lose access to free treatment, tests and vaccines, and this could affect the number of cases and deaths in the US.
With so many people getting sick around the world, something that could also change the direction of the pandemic in the US is another option. If more people get sick, there is a greater chance that another strain will emerge that is not protected by current vaccines and treatments.
“In the future, there may definitely be a new option that will create a new wave, and we will be forced to respond,” Lessler said. “That’s why it still makes sense to get vaccinated and revaccinated.”