On December 20th, at a news conference under The State Council's joint prevention and control mechanism, Xu Wenbo, director of the Chinese Center for Disease Control and Prevention, introduced that our country has been monitored that BF.7, BQ.1, XBB was introduced into our country in the past three months. There are more than 130 subbranches of Omichrong imported into our country, while 50 subbranches cause associated local cases or outbreaks of epidemic. Including BQ.1 and XBB, BQ.1 and its subbranches were detected in 49 cases in 9 governorates and XBB subbranches were detected in 11 cases in 3 governorates.
The latest study shows that XBB.1.5 has the same immune escape capacity as XBB.1, but the key mutation F486P gives it a higher human ACE2 receptor binding affinity -- ACE2 can be seen as the "gateway" for the novel coronavirus to enter human cells, meaning that XBB.1.5 is more likely to infect humans. Tests showed that breakthrough infection with BF.7 also failed to induce high levels of neutralizing antibodies against XBB.1 and XBB.1.5 in the presence of at least two doses of mRNA vaccine, making it difficult to prevent reinfection.
Experts at home and abroad predict that XBB.1.5 will become a major strain in the world in a short time, which requires close attention. Another important reason is that XBB.1.5 has almost the same ACE2 binding affinity as BA.2.75, which may make XBB.1.5 acquire more mutations like BA.2.75 in the future. However, XBB.1.5 has little immune pressure at present and will not evolve quickly.
Map of COVID-19 strain proportions for weekly surveillance in the United States. Source: U.S. Centers for Disease Control and Prevention website
The pathogenicity of XBB, BQ.1 and BQ.1.1 is similar to that of the previous strains, but the immune escape ability has been increased, according to CCTV's Weibo message. As a result, the resulting virus may spread faster than before. If these strains are encountered, the probability of reinfection mainly depends on two aspects: on the one hand, the overlap between the strains encountered again and BA.5 and BF.7. If the virus keeps mutating, the cross-protection effect is reduced, which may cause infection; The other is the level of autoantibodies.
Such dominant strains as BQ.1 and XBB have appeared in our country. What are the characteristics of these strains? Does it cause reinfection? How to deal with it?
On the issue of reinfection, Lu Hongzhou, president of the Shenzhen Third Hospital, said herd immunity was weak in preventing infection with new strains of BQ.1 and XBB, which would escape the immune barrier established by previous vaccination and natural infection.
"Although infection does not occur for a short period of time, such as three to four months, it is undeniable that new strains circulate or shorten the 'safe window' for reinfection. Therefore, in European and American countries, some people with poor immunity may be infected multiple times a year."
What should we do about it?
Lu Hongzhou says vaccination is still an important tool. Although the immune barrier established by vaccination is not effective against reinfection with the new strain, it still provides decent protection against severe illness and death.
As there is no evidence to suggest that the virulence of BQ.1 and XBB is significantly different from other Omicrone variants in terms of pathogenicity, vaccination is the best option for the general public, especially for high-risk groups such as the elderly.
