The other week in China’s Xinjiang, a fire flared up and killed 10 people in an apartment building. Questions over the need for an ongoing lockdown transformed into a full-on protest. People demanded that the government end the zero-COVID policy.
It’s not just that it’s hard to live in continual lockdown. From a public health standpoint, China’s zero-COVD strategy won’t be successful. SARS-CoV-2 is a global virus, points out Anna Durbin, an international health expert at Johns Hopkins who studies experimental vaccines. Even if the country could temporarily eliminate all cases, “you have travelers coming into China. They’re going to reintroduce it,” she says. Nearly 19 percent of China’s total population is adults age 60 and above. It’s crucial that public health efforts target this vulnerable population through vaccination, Durbin says. She’s in step with other experts in the U.S. In China, about 86 percent of adults over 60 have gotten at least two doses of the primary series, and around 68 percent of that age group has received their booster. Among people over 80, 65.8 percent are fully vaccinated, and just 40 percent have gotten a booster. In the U.S., 93.8 percent of the elderly population has completed a primary vaccine series against COVID.
China could do more than just ramp up vaccination—it could use more-effective vaccines. So far, eight COVID vaccines have been approved by its government. The two that are most commonly used are CoronaVac and Sinopharm, says William Moss, the executive director of the International Vaccine Access Center, also at Johns Hopkins. And they don’t stack up to the mRNA vaccines used in the U.S.
Both CoronaVac and Sinopharm are inactivated vaccines, meaning they use viral particles that have been killed. They were first approved for emergency use in mid-2021. Clinical trial data at that time, which was based on the original Wuhan strain of the virus, deemed CoronaVac 51 percent effective, and Sinopharm 79 percent effective. This is significantly lower than the efficacy of the Pfizer and Moderna mRNA vaccines, which were both over 90 percent at the time of approval.
Inactivated vaccines may not help the body secrete the highest quality of antibodies. That’s because the inactivation process uses harsh chemicals like formalin, says Durbin. This weakens the antibody binding site of the inactivated virus. Basically, it’s harder for your immune system to “practice” on an inactivated virus, versus the replicas of the viral spikes that an mRNA vaccine teaches the body to synthesize. The result is that inactivated vaccines “don’t give a broad immune response,” she says.
Compared with inactivated vaccines, the mRNA vaccines stimulate a more robust T-cell immunity, explains Durbin. (T-cell immunity is important because it can last longer.) A Singapore study suggests that the Pfizer mRNA vaccine elicits a better T-cell response than the Sinopharm vaccine does. The study concludes that those who receive Moderna’s mRNA vaccine are less likely to become infected than are those who get the inactivated CoronaVac and Sinopharm shots. Moreover, Hong Kong university researchers found that two doses of CoronaVac were not effective against omicron, while two doses of Pfizer’s mRNA vaccine helped the body mount a defense against the variant. Among the study’s 50 vaccine recipients (25 from Pfizer, 25 from CoronaVac), researchers weren’t able to detect antibodies against the variant in any of the adults who got CoronaVac shots. In contrast, 20 to 24 percent of Pfizer vaccine recipients had those antibodies.
An mRNA vaccine developed in China was rolled out in Indonesia for emergency use this September, but it has not yet been rolled out in China, and we don’t know the timeline for its approval there. Nor does China allow the use of mRNA vaccines developed in the West. Earlier this fall, Moderna refused China’s request to reveal its mRNA vaccine manufacturing technology.
Even without an mRNA vaccine, there is progress China could make on vaccination. A large study conducted by looking at case rates in Hong Kong’s population of 7.4 million also observed a lower efficacy of two doses of CoronaVac compared with two doses of Pfizer’s mRNA vaccine. However, three doses of CoronaVac almost matched the efficacy of three doses of Pfizer’s vaccine, at least in the short term. The study’s authors therefore recommend vaccinating the older population with a third dose of either CoronaVac or the Pfizer vaccine—though, again, the latter isn’t available in China.
Moss says that this is a well-designed study that makes a head-to-head comparison between the two types of vaccines available in China. But he mentions that the study period was relatively short and that it’s hard to determine the duration of protection after the third dose of CoronaVac. Regardless, he says, giving everyone a third dose would be beneficial. “I wouldn’t wait for mRNA vaccines to be introduced to China to vaccinate people,” says Durbin. “I would vaccinate people with what vaccine they have, to give them some immunity.”
There are several hurdles with implementing vaccination regimes, says Xi Chen, an associate professor of health policy at the Yale School of Public Health. Doctors are hesitant to order shots for older adults. In a survey conducted last year, only about 64 percent of doctors in Hong Kong encouraged their patients to get vaccinated against COVID.
What’s more, there are no robust vaccination campaigns to encourage people to get the shots, Chen adds.
China rolled out the world’s first inhalable COVID vaccine this October. Durbin says the intranasal vaccine can produce local immunity at the site where it enters the body—in this case the upper respiratory tract. While it’s possible these vaccines could help prevent the virus from spreading further, we cannot be certain that they’ll provide immunity deep in the immune system after they reach the lungs, says Durbin; this might not make them effective against severe infections. It’s unknown whether these nasal shots will armor recipients with long-lasting immunity. Nasal shots could act as a booster dose, says Moss. But ideally, people would get inoculated with two doses of an injectable vaccine first.
