Recently, many studies have shown that the three-shot vaccine is not very effective against Omicron, and people have a question: Do we need a fourth shot?
On February 19, Sun Yat-Sen University published a study on medrxiv examining the humoral immune response of four doses of inactivated vaccine.
Image source: medrxiv
Master of Neuroscience from Hokkaido University, Senior Medical Consultant of the Shengnuo Family, Weibo Popular Science University V Zhuang Shili and interpret the study.
Zhuang Shili: The background of this study is that the efficacy and immunogenicity of the current three-dose vaccine against Omicron is rapidly diminishing.
The researchers recruited 38 volunteers, all of whom are healthcare workers because the risk to frontline healthcare workers at Omicron is high. These health care workers had already received 3 doses of the inactivated vaccine (BBIBP), and the fourth dose was given 3 to 6 months after the third dose.
Research shows:
First, The four-shot vaccine is safe, and the probability of all adverse reactions is about 18%, mainly skin itching, dizziness, rashes, etc. But the probability of occurrence does not exceed 5.3%.
Second and fourth shots restore a weakened immune response.
Third, here comes the point,In the face of Omicron, the peak of neutralizing antibodies targeting RBD induced by the fourth dose was lower than that of the third dose. Although there are some antibodies targeting NTD, because Omicron also has a large number of mutations in the NTD region, these antibodies cannot compensate for the decreased neutralization activity caused by Omicron mutations.
This study shows that the immune response does not increase indefinitely, and that after repeated vaccination with a certain vaccine, the immune response focused on one subunit and immunity to other subunits is suppressed reaction transfer. And future vaccines should have more different epitopes that can induce neutralizing antibodies against different variants.
To put it simply, three shots of inactivated vaccine may be the limit.
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