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Dental care workers have very high risks of SARS-CoV-2 infection since most of the dental operations require aerosol-generating procedures which could potentially spread the virus in treatment areas. As a result, vaccination can be an important tool in protecting dental care workers from infection.
Objective: To investigate the adverse effects and immunogenicity after receiving third dose of viral vector (ChAdOx1) vaccine among dental care workers who fully vaccinated with inactivated (CoronaVac) vaccine.
Materials and Methods: Blood samples from 57 subjects were collected three times. Sixty days after fully vaccinated with CoronaVac (baseline), 14-21 days and 90-104 days after receiving ChAdOx1 booster dose. Blood samples were tested for immunity against SARS-CoV-2, including Anti-SARS-CoV-2 spike receptor-binding domain (RBD) IgG, Neutralizing antibody (sVNT) and Anti-nucleocapsid (N) protein IgG. Adverse effects were reported using questionnaire.
Results: At baseline, all subjects had an anti-RBD IgG titer greater than the cut-off value, while 43.8% had sVNT lower than the cut-off value. The anti-RBD IgG titer and sVNT appeared to increase in the second serum test yet reduced in the last test. At baseline, 40% of participants had anti-N IgG levels that were higher than the cut-off value. Anti-N IgG levels, along with the number of participants with values above the cut-off, have been declining in the other two serum tests. The majority of the participants experienced mild to moderate symptoms. Most of the symptoms subsided after a few days.
Conclusion: Receiving booster dose of ChAdOx1 after CoronaVac full vaccination can stimulate strong immune response against SARS-CoV-2 with no serious adverse effects. Although level of immunity declines within 3 months, neutralizing activity is still high. However, the protective efficacy tended to reduce overtime. To minimize the risk of infection, healthcare workers should follow prevention guidelines both inside and outside working hours.
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