Factors influencing breakthrough infection
fever
REGRESSION, INFLUENZA, FEVER CAUSED BY SARS-COV-2, CHRONIC DISEASE
Participants aged 18–59 years in the inactivated vaccine group were more likely to have digestive tract symptoms compared with who aged ≥60 years (Associations between participants’ characteristics and the breakthrough infection.Data are number of participants (%).Comparisons were performed using the Chi-squared test, unless marked as Associations between participants’ characteristics and the symptoms of breakthrough cases.Comparisons were performed using the Chi-squared test unless marked as A multivariable logistic regression analysis was performed to test the adjusted association between the main independent variable, defined as the type (inactivated vaccine or Ad5-nCoV) of the fourth vaccine dose vaccine and 1) the seropositivity rate of anti-RBD IgG and neutralizing antibodies against the BA.4/5 pseudovirus and 2) the risk of breakthrough infection with SARS-CoV-2. The association was tested after adjustment for sex, age, body mass index, exercise, sleep, underlying chronic disease, and influenza vaccination history.Compared with the participants who received the inactivated vaccine as the fourth dose, the participants who received Ad5-nCoV experienced an increase in the seropositivity rate of anti-RBD IgG [relative risk (RR) = 8.58; 95% CI, 3.53–20.86] and neutralizing antibodies against the BA.4/5 pseudovirus (RR = 24.52; 95% CI, 6.62–90.87) at 6 months after the last vaccination and were at a lower risk of fever caused by SARS-CoV-2 (RR = 0.41; 95% CI, 0.22–0.78). Compared with their male counterparts, female participants were at a higher risk of fever (RR = 2.44; 95% CI, 1.23–4.83) and general symptoms (RR = 2.44; 95% CI, 1.06–3.87) caused by SARS-CoV-2 and at a higher risk of symptom recovery time ≥3 days (RR = 2.45; 95% CI, 1.27–4.70). Compared with participants aged 18–59 years, participants aged ≥60 years had a lower seropositivity rate of neutralizing antibodies against BA.4/5 pseudovirus (RR = 0.18; 95% CI, 0.05–0.64) and were at a lower risk of digestive tract symptoms (RR = 0.29; 95% CI, 0.10–0.85). Compared with participants with a body mass index <24.0 kg/mMultifactorial analysis of antibody levels and breakthrough infection.Data are RR (95% confidence interval). Binary logistic regression was used for multifactorial analysis.