Sette A, Crotty S

Sette A, Crotty S. significantly over time. Further longitudinal studies are needed to identify whether the antibodies will decline or plateau at a lower level. and MannCWhitney; and MannCWhitney; and MannCWhitney; em p /em \values? ?0.0001 are reported as exact RS 504393 numbers A small number of HCWs (5%) had an autoimmune disease. No differences were found in IgG positivity between HCWs with immune\mediate diseases and those who did not. In the same way, no significant difference in antibody titers were found between the groups (Figure ?(Figure4B4B). 4.?DISCUSSION This study demonstrated that the first dose of CoronaVac already elicits a good immune response in HCWs. The antibody status of HCWs in this phase might reflect community\acquired immunity, resulting from SARS\CoV\2 exposure in daily medical practice. The second dose of vaccine induced a powerful boost in the humoral immunity. However, 6?months after the second dose, the antibody response decreased significantly. The decline of antibodies is expected as not all vaccine\induced plasmablasts commit or are maintained as long\lived memory plasma cells. 25 Thus, the success of vaccine is dependent on the generation and maintenance of immunological memory. 26 According to the findings, the rate of antibody positivity and the amount of antibody titers were significantly higher in females. The difference in antibody responses is one of the most well\conserved sex differences in immunology contributing to susceptibility to infectious diseases and responses to vaccines in males and females. 27 Sex\based immunological differences can explain the male\biased COVID\19 mortality 28 and the more robust female immune response to COVID\19 vaccines reported in the literature. 29 , 30 , 31 , 32 Patient age has been identified as a risk factor for severe illness and death in COVID\19. Vaccine responses are diminished in the older adults due to immune senescence. In this study, although there was no significant difference in antibody titers between the age groups, the participants 51?years exhibited the lowest IgG anti\S titers, mainly after the first dose of vaccine. However, after ETS2 the second dose of vaccine, the immunogenicity reached a level close to the others age group. Bayram et al. 29 and Bueno et al. 33 also reported relatively low seropositivity in individuals aged 60?years and older, after the first dose of CoronaVac, but similar to that found in younger individuals after the second dose. Thus, in the present study two doses of CoronaVac were capable of induction an antibody response in people 51?years old. In addition, the results show that age has a less significant effect at later time point, 6?months after the second dose of vaccine. Similar finding was reported by Naaber RS 504393 et al. 25 evaluating the effect of age in COVID\19\mRNA vaccinated individuals. Therefore, the findings indicate the benefit of the second dose for older people and its effect to level up the short\term vaccination response. Although, the long\term evidence on the postvaccination antibody persistence in older populations remains to be studied. After the vaccination, previously infected participants had a significantly higher antibody levels than previously uninfected participants. Post\vaccination antibody levels positively correlated with previous infection were described by other studies. 29 , 34 , 35 , 36 , 37 Interestingly, an increase of antibodies in previously infected participants was not observed after the second dose of vaccine. HCWs with a history of COVID\19 seems to reach a peak of antibodies already in the first dose, so that a second dose does not increase the response. This phenomenon can be explained by the fact that in a conventional multidose vaccine schedule, the first dose generates a primary immune response, and the second dose produces the boosted anamnestic response. In individuals who experienced COVID\19, their previous infections will serve as a priming dose of antigen; the first vaccination dose then, in effect, becomes the booster shot. 38 Additionally, several studies make note that the second dose in this situation provides virtually no additional boost to antibody levels. 29 , 38 , 39 , 40 , 41 , RS 504393 42 , 43 , 44 These findings may suggest that people who experienced COVID\19 can benefit from one just dose of CoronaVac..