BEIJING (Reuters) – A small Chinese study detailed in The Lancet Infectious Diseases journal showed that neutralising antibodies against most Omicron sublineages currently circulating were largely undetectable after two doses of a Sinopharm COVID-19 vaccine, with a booster shot only partly restoring them.
The study comes as China, which has approved only locally developed COVID shots including the Sinopharm vaccine, strives to improve vaccination rates, maintaining a “dynamic zero COVID” policy aimed at eradicating all outbreaks while many countries have adopted an approach of learning to live with the virus.
The vaccine, BBIBP-CorV, is one of the two Sinopharm COVID shots approved for use in China, and is also the main shot that the state-owned firm has exported.
In serum from 25 individuals who received two doses of BBIBP-CorV vaccine, neutralising activity against the Omicron BA.1, BA.2, BA.2.11, BA.2.12.1, BA.2.13, BA.4, and BA.5 sublineages “was not or only minimally detectable”, researchers reported in the study published on Monday.
Neutralising activity against those versions of Omicron was observed in just 24-48% of subjects who received a BBIBP-CorV booster shot after the two-dose primary series, researchers said.
The rate improved slightly, to 30-53%, for those who received a third shot made by a unit of Chongqing Zhifei Biological Products, ZF2001, a vaccine approved for use in China, according to data from another group of 30 subjects.
Still, geometric mean titres of neutralising antibodies were 4.6 – 17.1 times lower against Omicron lineages than against the earlier D614G version of the coronavirus spike protein.
The BA.2.12.1 sublineage showed significantly more resistance than BA.2 to a BBIBP-CorV booster, and the BA.2.11, BA.2.12.1, and BA.2.13 sublineages showed significantly more resistance than BA.2 to a ZF2001 booster, the study team notes.
SOURCE: https://bit.ly/3HFLHuU The Lancet Infectious Diseases, online June 20, 2022.