Objective To investigate the levels of serum antibodies against novel coronavirus （SARS-CoV-2） in healthcare workers after one month of natural infection， to explore the influencing factors and their correlations with the levels of antibodies， and to provide reference for strengthening the protection of healthcare workers and preventive intervention in Pudong New Area in Shanghai.
Methods Venous blood samples were collected from 1 102 medical staff in Pudong hospitals one month after infection. The serum levels of new coronavirus specific antibodies IgM， IgG and neutralizing antibodies were detected by chemiluminescent immunoassay. The information of gender， age， position， infection severity， vaccination， basic diseases and use of immunosuppressants were obtained by questionnaire to explore the influencing factors and their correlation with the antibody level.
Results One month after natural infection， 99.00% （1 091/1 102） of the subjects were found to be positive for IgG antibody against the new coronavirus， 17.79% （196/1 102） of the subjects were IgM antibody positive， and 99.00% （1 091/1 102） of the samples were positive for the neutralizing antibody. The level of antibody might be influenced by the severity of infection， the time of the last dose of vaccination， and the long-term use of immunosuppressants. The more severe the disease， the stronger the neutralizing antibody response. The antibody level in the people who received the final dose of vaccine within 6 months was higher than that of the people who received the vaccine 6 months ago， and the difference was statistically significant. The antibody levels were low in the subjects who received long-term immunosuppressants.
Conclusion The specific IgM， IgG and neutralizing antibody were found， one month after infection， in the medical workers in Pudong New Area， Shanghai， and the antibody titers were high， which had a good protective effect. The antibody level of the people who were vaccinated within 6 months was higher， it is recommended that people who receive the last vacination more than 6 months should be re-vaccinated with the booster vaccine， to improve the autoimmunity against the novel coronavirus.
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