Immune Level after Sinovac Vaccine Immunization for Novel Coronavirus in Prapokklao Hospital

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Watcharin Chirdchim
Patpong Udompat
Surasak Im-iam
Chanthanee Nitikarun


BACKGROUND: The Coronavirus disease (COVID - 19) outbreak is rapidly and severely affecting public health systems around the world. Healthcare workers are the front line of contact with people who are at risk of infection. As a consequence, vaccination for health workers has taken place in all countries. Furthermore, the surveillance of antibodies after immunization is necessary because of the new pandemic. The vaccine used is also a new form approved for emergency use.

OBJECTIVE: To evaluate the level of antibodies after receiving the Sinovac Vaccine.

METHODS: A cross - sectional study was conducted in Prapokklao Hospital, Chanthaburi Province, Thailand on healthcare personnel who had received the second dose of the Sinovac vaccination.  Blood was collected for more than four weeks to check the antibody levels. The estimation of the sample was computed using a two - tailed level that had a significance level of 0.05 (alpha = 0.05), 90% power given by the 50% theory, and expected 60 - 70% increase in the calculated immune level. The sample size was calculated to be 62 - 250 people; however, the researchers chose a sample size of 200 people from a total of 2,000 personnel.

RESULTS: The 200 sample population had a full examination for antibodies. The results demonstrated a mean of 106.47 ± 91 unit/ml (min = 4.58; max = 821), a percentile of 25 = 46.2, percentile of 50 = 89.8, percentile of 75 = 145.5, and percentile of 50 = 100 n, respectively. However, 146 of the participants did not reach the convalescent plasma levels. In addition, with regard to the duration and level of immunity, the immune levels decreased over time and when the involved factors were controlled, the immune levels decreased by 0.56 per day but were not statistically significant (p = 0.4). Nevertheless, increased age resulted in a statistically significant decrease in the immune levels (p = 0.009).

CONCLUSIONS: As a result of the reduction of immunity, a booster dose of vaccination should be required to deal with further severe outbreak situations to prevent the loss of medical personnel.


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