RESUMEN
Objective To analyze IgG test results of serum SARS-CoV-2 antibody in people after booster vaccinations against SARS-CoV-2, and to provide a basis for the booster vaccination. Methods There were 314 healthy individuals who had been vaccinated with the COVID-19 vaccine. Depending on their inoculation situation, they were divided into three groups:the booster injection group(1 week to 2 months after booster vaccination)of 205 cases, <180 days after two doses group(<180 days after two doses of COVID-19 vaccine)of 49 cases, and >180 days after two doses group(>180 days after two doses of COVID-19 vaccine)of 60 cases. The positive rate of IgG in serum of the three groups was measured using the colloidal gold method. Results The serum COVID-19 antibody IgG positive rates were 83.9% in the booster injection group, 18.4% in the <180 days after two doses group, and 5.0% in the >180 days after two doses group, with statistically significant difference between any two groups(all P < 0.05). In the booster injection group, the serum COVID-19 antibody IgG positive rate was 85.2% in people who received a booster injection more than a month, while those who received a booster injection less than a month had a positive rate of 75.9%, and there was no significant difference between these two groups(P > 0.05). In the booster injection group, the positive rates of serum COVID-19 antibody IgG were 85.1% in males and 82.4% in females, with no significant difference(P > 0.05). In the booster injection group, people at the age of 18 and 50 had a positive serum COVID-19 antibody IgG rate of 86.0%, while those over 50 had a positive rate of 58.3%, and there was significant difference between them(P < 0.05). Conclusions Compared with two injections of the COVID-19 vaccine, the booster injection can significantly increase the positive rate of the antibody IgG of COVID-19, which results in a stronger immune response. There is a lower IgG positive rate of COVID-19 antibodies in those aged over 50 years following the booster dose of COVID-19 vaccine than in those aged 18- 50 years.