Here we show that even previously infected and fully vaccinated subjects with high anti-S IgG titers are susceptible to infection by VOC, highlighting that immune responses induced by either natural infection or vaccination may not be sufficient to prevent infection by SARS-CoV-2 variants.
For this study we selected 72 SARS-CoV-2 recently tested positive individuals with nasopharyngeal swabs collected between mid-January and March 2021 with SARS-CoV-2 RT-qPCR Ct values <30. These include both cancer patients and healthcare workers (HCW) from the Brazilian National Cancer Institute (INCA), Rio de Janeiro, Brazil. Of those 72 subjects, six were vaccinated prior the current infection and two out of those six were also reinfection cases. Another three subjects also represented reinfections, showing a previous infection during the first wave of the pandemic in Brazil.
Six HCW included in this study have been fully or partially vaccinated with one of the vaccines available in Brazil, either CoronaVac (Sinovac/Butantã) or ChAdOx1-S/nCoV-19 (AstraZeneca/Oxford/Fiocruz). All six tested positive for SARS-CoV-2 RT-qPCR after at least one vaccine dose and reported mild symptoms during infection.