ABSTRACT
Introduction: In March 2020, WHO, after assessing the global spread of SARS-CoV-2 infection, declared the outbreak of COVID-19 a pandemic. Several vaccines have been developed during these years, but some studies have shown that their efficacy decreases significantly over time, so a booster dose was required. In November 2021, the administration of the third dose (booster) of the SARS-CoV-2 vaccine was made mandatory. With our study, we want to describe the antibody trend up to 6 months after the booster dose. Material(s) and Method(s): The study population consisted of 255 healthcare workers (median age 47 years, 66,3% women) of the Pederzoli Hospital (Peschiera del Garda, Verona, Italy), receiving a booster dose of Pfizer COVID-19 vaccine BNT162b2 (Comirnaty). Serum samples were collected before the booster dose (baseline), one month (T1), and six months (T2) afterwards. The serum levels of anti-SARS-CoV-2 spike trimeric IgG were assayed with DiaSorin Trimeric spike IgG (DiaSorin, Saluggia, Italy). Results were presented as the median and interquartile range (IQR) or as a ratio with baseline anti-SARS-CoV-2 antibodies value. Result(s): In our population at T1 (median 7730 BAU/mL;IQR 4462,5-12350) we observed an increase (32,6-folds) of anti-SARS-CoV-2 spike trimeric IgG compared to baseline (median 237 BAU/mL;IQR 129,5-416). At T2 (median 3720 BAU/mL;IQR 1502,5-9495) there was a 51,9% decrease from T1. During the observation period (after the booster dose), 111 subjects resulted positive for a nasopharyngeal swab. This subgroup showed a 16.6% increase in antibody titer between T1 and T2, while the non-infected subjects had a significant decrease (73.2%). Furthermore, in subjects aged 50 years or older, the antibody titer dropped by 60.8% from T1 to T2 compared with the titer of subjects <50 years which decreased by 42.4%. Conclusion(s): the booster dose of Pfizer COVID-19 vaccine BNT162b2 triggers an excellent immune response in all subjects included in this study. However, the serum levels of anti-SARS-CoV-2 antibodies gradually lower six months after administration, but they still remain discreetly high. Since the decrease is more pronounced in elderly subjects, the assumption to carry out a second booster dose, at least in the most fragile subjects, becomes more concrete.
ABSTRACT
Abstract: The differences of the epidemiology (incidence, case-to-death rate, mortality, etc) of COVID-19 between USA and Italy are analyzed taking into account the social, economic and sanitary characteristics of the two countries, both severely hit be the pandemic; and the causes of the so many different behaviors of the disease in each of them are discussed and explained.