Evaluation of antibody response anti SARS-Cov-2: A retrospective observational study (Marche-Italy)

COVID-19 has hit every country in the world. Almost a quarter of a billion cases and nearly 5 million deaths reported globally as of late September 2021. Compared to over 6 billion doses of COVID-19 vaccine administered, the pandemic does not seem to disappear. The duration of protective immunity is currently not defined. Primary immune responses are inevitably declining and the continuous transmission of increasingly worrying viral variants.

The primary objective of the study is to evaluate the antibody response at 120 and 180 days in employees of an hospital of Marche (Italy) who have completed the vaccination cycle with Pzifer-Biontech vaccine and to highlight the correlation with quantitative and qualitative variables. The secondary objective is to study the nature and frequency of adverse events in relation to variables such as comorbidity, age, gender, working areas and developed antibody titer.

An observational retrospective study was carried out to evaluate the antibody response at 120 and 180 days. Subjects receiving a double dose of vaccine at least 21 days apart and those receiving the second dose of the same vaccine between 18 January 2021 and 31 March 2021 shall be considered. The study included non-probability sampling of convenience. All parties have provided informed written consent to access personal and clinical data.

The sample is composed by 1.115 subjects. The results of the study reveal an important immune response detected by IgG dosage, both at 120 and 180 days after the second dose of Sars-Cov-2 vaccine mRNA BNT162b2 vaccine (Pzifer-Biontech), other than very rare exceptions. Antibody values are higher among hospital workers compared to those working in other areas, both 120 and 180 days. These values are even higher in the health professionals who provide assistance in wards with positive Covid patients, both at 120 days (p=0.06) and at 180 days; the mean values of IgG are statistically higher in direct assistance of Covid patients at 180 days(p=0.029). The most frequent adverse drug events after the second dose of vaccine were pain at the site of inoculation of the vaccine (70.7%), fatigue (35%) and arthralgia (19%). It was finally shown that people with diabetes or smokers had an average antibody response statistically lower than 120 days and 180 days from the second dose.

This study leads to the conclusion that the second dose of vaccine Sars-Cov-2 vaccine mRNA BNT162b2 vaccine allows a consistent antibody response. Further multicentric studies are needed to investigate the antibody response to vaccination Sars-Cov-2 mRNA BNT162b2.