Background: The observational test-negative study design is used to estimate vaccine effectiveness against influenza virus infection. An important assumption of the test-negative design is that ...

OBJECTIVESTo determine whether time elapsed since the second injection of the Pfizer-BioNTech BNT162b2 mRNA vaccine was significantly associated with the risk of covid-19 infection after vaccination ...

Cases and controls were matched one-to-five according to sex, 10-year age group, nationality, number of coexisting medical conditions, calendar week of testing, method of testing (polymerase chain ...

The BA.2.75 sublineage of the B.1.1.529 (omicron) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may escape neutralizing antibodies. The BA.2.75 sublineage (primarily the BA.2 ...