Vaxzevria

Anonymized blood samples were collected at the laboratory of Virology of the Toulouse University Hospital. Biobanking was done at the Center of Biological Resources of the Toulouse University Hospital (certified according to NF S96-900 standards). All French law ethical requirements were respected.
One hundred sera from patients hospitalized in January 2019 were used as anti-SARS-CoV-2 antibody-negative samples. The two panels of sera from infected patients represented “recent” and “late” infections. All SARS-CoV-2 infections were determined by a positive RT-PCR on a nasopharyngeal sample. Thirty-five recent samples were taken 15 to 35 days postinfection in patients hospitalized with COVID-19 (patients sampled between 1 April 2020 and 23 March 2021). Late samples (150) were taken more than 180 days postinfection in health care workers recovered from a SARS-CoV-2 infection (patients sampled 30 November to 4 December 2020). In this patient cohort, one-third were asymptomatic at the time of diagnosis of SARS-CoV-2 infection (34 (link)). We also established two groups of vaccinated subjects: one had been given two doses of the Comirnaty (Pfizer-BioNTech) vaccine, and the other had had one dose of the Vaxzevria (AstraZeneca) vaccine. Samples were collected at least 1 month after receiving the last dose.
The demographic characteristics of patients are listed in Table 3.

By questionnaire, participants were asked whether they had undergone a SARS-CoV-2 test by trained staff (at medical practitioner, test site, or hospital) and whether this test was positive: ever (BL), since 17 July 2020 (FU1), or since 27 November 2020 (FU2). Self-reported positive tests were validated by health authorities. At FU2, participants were also asked whether they were vaccinated against SARS-CoV-2 and, if yes, how often, which vaccine, and when. Individuals were classified as fully vaccinated, if they had two vaccinations by Comirnaty (BionNTech, Mainz, Germany), SpikeVax (Moderna, Cambridge, MA, USA), or Vaxzevria (AstraZeneca, Cambridge, UK) ≥ 14 days before their respective blood draw.

For the assessment, 81 serum samples were obtained after the first vaccination against SARS-CoV-2, 70 serum samples after the second vaccination against SARS-CoV-2 and 40 samples from individuals with a history of natural infections with the SARS-CoV-2 virus. For the vaccinees, who were participants in the COV-ADAPT study [52 ], anti-SARS-CoV-2-NCP-ELISA (IgG) (Euroimmun, Lübeck, Germany) excluded anti-nucleocapsid-IgGs (NCP) to rule out infection with SARS-CoV-2 before vaccination. Negative results were a prerequisite for being included in the assessment. Vaccinations had been performed with various combinations of Vaxzevria (AstraZeneca, Cambridge, UK) or Comirnaty (Biontech, Mainz, Germany). Infections that occurred during a period when the Wuhan wild type variant was prevalent had been ensured by real-time PCR. Based on the various combinations of possible expositions, three different exposition types, i.e., natural infection, exposure to one vaccination and exposure to two vaccinations, were defined.

In the present study, 43 lactating women that had no diagnosis of laboratory-confirmed COVID-19 (with an antigen rapid test or RT-qPCR test) and were scheduled to receive a COVID-19 vaccine were recruited (n = 28 with BNT162b2 mRNA/BioNTech/Pfizer, n = 6 with mRNA-1273/Moderna and n = 9 with Vaxzevria/AstraZeneca). The vaccinated participants had received two or three doses of the mRNA vaccines. Control milk samples were obtained from the same individuals before vaccination and used as controls to establish positive cut-off values for each assay. Samples were also collected 1 day before the second dose, 3 weeks after the second dose, and, in some participants (n = 10), 3 weeks after the booster (3rd dose) dose to determine antibody levels. All samples were collected in sterile tubes, stored immediately at −20 °C and later divided into 1.5 mL aliquots and stored at −80 °C until used. On the collected breast milk samples, anti-SARS-CoV-2 IgA, IgG, and SIgA were evaluated prior and after simulation of infant GI digestion. The study design overview is shown in Figure 1.
In addition to breastmilk samples, clinical and demographic characteristics were also collected. Participants received information and gave written informed consent before enrolment. All procedures were approved by the Cyprus National Bioethics Committee (protocol number EEBK/EΠ/2021/24).