In much of the world, hard lockdowns to curb transmission of SARS-CoV-2 seem a thing of the past. Not in China. On April 19th, Shanghai entered its third week of a strict lockdown, having registered 19,442 new transmissions the day before (ten deaths have been recorded in the current wave). The disruptions clearly have a huge human and economic cost, but the government appears to have no clear plan B. The main problem is that the elderly in China are insufficiently vaccinated. But it does not help that at one or two doses, at least one of its vaccines is less effective than an mRNA shot widely available elsewhere.
A study by the University of Hong Kong has for the first time compared the effectiveness of China’s Sinovac vaccine with the mRNA vaccine developed by BioNTech against the Omicron variant of the virus (made with Pfizer in most countries, and Fusan Pharma in Hong Kong). Both vaccines work: at three doses they were estimated to offer over 90% protection against severe disease and death across all age groups. But without a booster, significant differences between the two vaccines emerged. With two doses, the BioNTech shot was 75-96% protective across age groups. Sinovac, however, had a range of 44-94%. For those aged 80 and above, the differences were even starker. The best estimates were then 85% for the BioNTech vaccine and 60% for Sinovac. In other words, both vaccines offered increasing protection with each dose, but not equally.
The estimates are subject to the usual caveats. The authors cautioned that the higher effectiveness of the third dose may in part be due to how recently it was administered. Mild infections may have also gone undetected, and links between vaccination and risky behaviour and underlying conditions also play a part. Though not as rigorous as a head-to-head clinical trial, the study provides the best evidence so far of how these vaccines do against Omicron.
The Chinese shot may also be less effective at limiting infections. For those aged under 60 in Hong Kong, the German-developed vaccine significantly limited even mild cases of Omicron after just one jab. In contrast, for mild infections, Sinovac’s shot had no detectable impact after one or two doses, and offered only about half the protection of the mRNA vaccine after three (about 40%).
The implications for China are grim. Just slightly more than 50% of the population has been boosted and, by March 17th, less than half of those aged over 70 had received a third dose, according to the country’s National Health Commission. Many old people are not vaccinated at all. China initially approved shots only for healthy people under 60, leading to concerns that they might be dangerous. With vaccines that do a poorer job of limiting infection, transmission will be high. Although the Chinese government on April 4th cleared another domestic mRNA vaccine candidate for clinical trials, these vaccines are not in arms yet. A push to get the elderly vaccinated, and those already with jabs boosted, seem the only way back to normal.