Assessment of early and post COVID-19 vaccination antibody response in healthcare workers: a multicentre cross-sectional study on inactivated, mRNA and vector-based vaccines.

In this multicentre study, we compared the status of antibody production in healthcare personnel (HCP) before and after vaccination using different brands of COVID-19 vaccines between March 2021 and September 2021. Out of a total of 962 HCP enrolled in our study, the antibody against the S1 domain of SARS-CoV-2 was detected in 48.3%, 95.5% and 96.2% of them before, after the first and the second doses of the vaccines, respectively. Our results showed post-vaccination infection in 3.7% and 5.9% of the individuals after the first and second doses of vaccines, respectively. The infection was significantly lower in HCP who presented higher antibody titres before the vaccination. Although types of vaccines did not show a significant difference in the infection rate, a lower infection rate was recorded for AstraZeneca after the second vaccination course. This rate was equal among individuals receiving a second dose of Sinopharm and Sputnik. Vaccine-related side effects were more frequent among AstraZeneca recipients after the first dose and among Sputnik recipients after the second dose. In conclusion, our results showed diversity among different brands of COVID-19 vaccines; however, it seems that two doses of the vaccines could induce an antibody response in most of HCP. The induced immunity could persist for 3-5 months after the second vaccination course.

Re-positive PCR of SARS-CoV-2 in health care persons during COVID-19 pandemic.

Reinfection rate with SARS-CoV-2 and degree of protection by the induced antibody after the first episode of the infection is not well known, so it makes a big dilemma for health care personnel (HCP) who work in the front line of combating SARS-CoV-2. In this study, we investigated the frequency of SARS-CoV-2 redetection among HCP after the initial onset of the infection in a children's hospital during one year. Out of 131 seropositive HCP, 13.7% of them were symptomatic and PCR positive during 74-360 days after first sampling. Analysis of demographic data of seropositive HCP showed a correlation between a higher number of family members, higher body mass index, and the existence of underlying diseases with SARS-CoV-2 redetection. In conclusion, reinfection is one of the important problems in the SARS-CoV-2 pandemic. Research on this topic can help us to find answers to questions for estimating the duration of human protection with produced immunity after the infection or vaccination.