Recently, many studies have shown that the effectiveness of the three-dose vaccine on Omicron is not high, and people have a question: Do we still need a fourth dose?
On February 19, Sun Yat-sen University published a study in medrxiv that explored the humoral immune response of a four-dose inactivated vaccine.
Image source: medrxiv
Hokkaido University Master of Neuroscience, a senior medical consultant of Sheng Nuo, Weibo Science Popularization University V Zhuang Shilihe interpreted this research.
Zhuang Shilihe: The background of this study is that the effectiveness and immunogenicity of the three-shot vaccine against Omicron are rapidly weakening.
So the researchers recruited 38 volunteers, all of whom were health care workers, because the risk of facing Omicron's frontline health care workers was high. These healthcare providers have received 3 doses of inactivated vaccine (BBIBP) and a fourth dose 3 to 6 months after the third dose.
Studies have shown that:
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 is not more than 5.3%.
Second, a fourth dose of the vaccine restores a weakened immune response.
Third, the point is that in the face of Omicron, the neutralizing antibody peak of the targeted RBD induced by the fourth needle is lower than that of the third needle. Although there are still some antibodies that target NTD, these antibodies cannot compensate for the decline in neutralization activity caused by Omicron mutations because Omicron also has a large number of mutations in the NTD region.
This study showed that the immune response does not increase indefinitely, and after repeated vaccination of a certain vaccine, it inhibits the immune response concentrated in one subunit and the transfer of the immune response to other subunits. Future vaccines should have more different epitopes of antigens that can induce neutralizing antibodies against different variants.
To put it simply, a three-shot inactivated vaccine may be the limit.
Curated: Ground cat
Executive Producer: Gyouza