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The mRNA vaccine BNT162b2 has proven highly effective and currently many millions are being vaccinated. There are limited and conflicting data from immunogenicity studies on the effects of age, gender, vaccination side effects (VSE), risk factors for severe COVID-19 (RFS-COV), obesity (BMI) and previous SARS-CoV-2 (Pr-CoV) Moreover, immunogenicity data from COVID-19 patients comparing various disease categories of natural infection i.e. asymptomatic vs mild vs moderate vs severe infection are sparse, and include limited number of individuals.This study included 871 vaccinated health care workers (HCW) and 181 patients with natural infection. Immunogenicity was assessed by a quantative assay measuring anti-SARS-CoV-2 against the RBD domain of the spike protein (anti-RBD) and anti-SARS-CoV-2 against nucleocapsid protein (anti-N). Samples were collected 1-2 weeks after completion of the 2nd dose in the vaccinated HCWs and 15-59 days post symptoms onset in patients with natural infection.The concentration of anti-RBD in vaccinated individuals after multivariable analysis was significantly associated with age, gender, VSE and Pr-CoV. Specifically, anti-RBD median levels (95% CI) were lower by 2,466 (651-5,583), 6,228 (3,254-9,203) and 7,651 (4,479-10,823) AU/ml in 35-44, 45-54, 55-70 yrs respectively, compared with 18-34 yrs group. In females, median levels of anti-RBD were higher by 2,823 (859-4,787) compared with males, in individuals with VSE were higher by 5,024 (3,122-6,926) compared with no VSE, and in HCWs with Pr-CoV were higher by 9,971 (5,158-14,783) AU/ml compared with HCWs without Pr-CoV.Among individuals with natural infection, the median anti-RBD levels were 14.8 times higher in patients with critical COVID-19 infection compared with non-hospitalized individuals. The ratio of anti-RBD in vaccinated individuals versus those with natural infection varied from 1.0 up to 19.4 according to the clinical subgroup of natural infection.This study proves the high immunogenicity of BNT162b2 vaccine although its sustainability remains to be seen. The use of comparative data from natural infection serological panels, expressing the clinical heterogeneity of natural infection may facilitate early decisions for vaccine evaluation in clinical trials.

BNT162b2 has proven to be highly effective, but there is a paucity of data regarding immunogenicity factors and comparison between response to vaccination and natural infection. This study included 871 vaccinated healthcare workers (HCW) and 181 patients with natural infection. Immunogenicity was assessed by measuring anti-SARS-CoV-2 against the RBD domain of the spike protein (anti-RBD). Samples were collected 1–2 weeks after vaccination or 15–59 days post-onset of symptoms. Post-vaccine anti-RBD concentrations were associated with age, gender, vaccination side-effects (VSE) and prior infection (Pr-CoV). Anti-RBD median levels (95%CI) were lower by 2466 (651–5583), 6228 (3254–9203) and 7651 (4479–10,823) AU/mL in 35–44, 45–54, 55–70 yrs, respectively, compared with the 18–34 yrs group. In females, the median levels were higher by 2823 (859–4787), 5024 (3122–6926) in individuals with VSE, and 9971 (5158–14,783) AU/mL in HCWs with Pr-CoV. The ratio of anti-RBD in vaccinated individuals versus those with natural infection varied from 1.0 to 19.4. The high immunogenicity of BNT162b2 is verified, although its sustainability has yet to be elucidated. The use of comparative data from natural infection serological panels, expressing the clinical heterogeneity of natural infection, may facilitate early decisions for candidate vaccines to be evaluated in clinical trials.

Objectives The ‘3-day rule’ for stool culture ordering suggests that only selected inpatients with nosocomial diarrhoea should have stool cultures for enteropathogenic bacteria (EPBs). Patients with haematological malignancies are not included in this group. We have analysed the ordering of stool cultures at Laikon Hospital to investigate whether all patients with haematological malignancies should be excluded from the 3-day rule. Methods We have retrospectively analysed all inpatient stool specimens sent to the microbiology laboratory for enteropathogenic bacteria culture at Laikon Hospital, Athens, Greece, between January 1, 2014 and December 31, 2014. We classified stool cultures sent after the third day as ‘appropriate’, ‘excluded’ with standard rule, ‘excluded’ with haematological malignancies, and ‘inappropriate’. Results During the study period, 1101/1593 inpatient stool cultures (69.1%) had been ordered after the third day of hospitalization. The total yield for inpatient EPB stool cultures was 0.7% (11/1593). The yield for ‘appropriate’ cultures was significantly higher than the yield of all ‘excluded’ specimens (3.7% (3/81) versus 0.3% (2/585), p 0.018) and to ‘inappropriate’ orders (3.7% (3/81) versus 0.0% (0/485), p 0.0028). There was no difference in the yield between specimens ‘excluded’ with the standard rule and ‘excluded’ with haematological malignancies. Conclusions In our hospital, the yield of stool cultures from patients with haematological malignancies is similar to that of patients ‘excluded’ from the standard 3-day rule. If patients with haematological malignancies were not excluded from the rule, we would reduce the inpatient stool cultures by 13.6% (217/1593) at the cost of missing one positive stool culture.