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During the COVID-19 pandemic, Portugal has experienced three distinct SARS-CoV-2 infection waves. We previously documented the prevalence of SARS-CoV-2 immunity, measured by specific antibodies, in September 2020, 6 months after the initial moderate wave. Here, we show the seroprevalence changes 6 months later, up to the second week of March 2021, shortly following the third wave, which was one of the most severe in the world, and 2 months following the start of the vaccination campaign. A longitudinal epidemiological study was conducted, with a stratified quota sample of the Portuguese population. Serological testing was performed, including ELISA determination of antibody class and titers. The proportion of seropositives, which was 2.2% in September 2020, rose sharply to 17.3% (95% CI: 15.8-18.8%) in March 2021. Importantly, circulating IgG and IgA antibody levels were very stable 6 months after the initial determination and up to a year after initial infection, indicating long-lasting infection immunity against SARS-CoV-2. Moreover, vaccinated people had higher IgG levels from 3 weeks post-vaccination when compared with previously infected people at the same time post-infection., (© 2021 The Authors. European Journal of Immunology published by Wiley-VCH GmbH.)

In September 2020, we tested 13,398 persons in Portugal for antibodies against severe acute respiratory syndrome coronavirus 2 by using a quota sample stratified by age and population density. We found a seroprevalence of 2.2%, 3-4 times larger than the official number of cases at the end of the first wave of the pandemic.

Although Staphylococcus aureus is a major cause of outbreaks in neonatal intensive care units (NICUs), there are no studies on the epidemiology of S. aureus isolates responsible for infection in Portuguese NICUs. Between July 2005 and December 2007, a total of 54 methicillin susceptible S. aureus (MSSA) isolates were recovered from 16 infected infants, parents, health care workers (HCWs), and the environment in a level III NICU. Isolates were characterized by pulsed-field gel electrophoresis (PFGE), spa typing, and multilocus sequence typing. Virulence determinants were detected by multiplex polymerase chain reaction. Three major MSSA clones were endemic in the NICU, representing 70% (n=38) of the isolates: PFGE type A-ST5 (n=17); type B-ST30 (n=12); and type C-ST1 (n=9). Leukotoxins and hemolysins were present in all isolates, although none of them carried PVL. HCWs, plastic folders protecting clinical files, and mothers' nipples were identified as potential reservoirs and/or vehicles of dissemination of S. aureus. Consequently, additional infection control measures were implemented in this NICU.