BACKGROUND A rapid increase in coronavirus disease 2019 (Covid-19) cases due to the omicron (B.1.1.529) variant of severe acute respiratory syndrome coronavirus 2 in highly vaccinated populations has aroused concerns about the effectiveness of current vaccines. METHODS We used a test-negative case–control design to estimate vaccine effectiveness against symptomatic disease […]
A new study from the Center for Disease Control and Prevention confirms what Mayo Clinic and other experts have been saying: COVID-19 booster vaccinations improve protection against severe illness and hospitalization. The study examined people who had three doses of the Moderna or Pfizer COVID-19 vaccines, as well as whether it was a booster dose or […]
COVID-19 vaccines appear slightly less effective in preventing severe disease and death but do provide “significant protection,” the World Health Organization (WHO) said on Tuesday. The Omicron variant first detected in South Africa and Hong Kong last month has now been reported by 77 countries and is probably present in […]
Background To date, coronavirus disease 2019 (COVID-19) becomes increasingly fierce due to the emergence of variants. Rapid herd immunity through vaccination is needed to block the mutation and prevent the emergence of variants that can completely escape the immune surveillance. We aimed to systematically evaluate the effectiveness and safety of […]
Summary What is already known about this topic? Studies suggest that immunocompromised persons who receive COVID-19 vaccination might not develop high neutralizing antibody titers or be as protected against severe COVID-19 outcomes as are immunocompetent persons. What is added by this report? Effectiveness of mRNA vaccination against laboratory-confirmed COVID-19–associated hospitalization […]
Summary What is already known about this topic? Persons aged 12–18 years are eligible to receive COVID-19 vaccine. Currently, data are lacking on real-world vaccine effectiveness against COVID-19 hospitalization in adolescents. What is added by this report? Among hospitalized U.S. patients aged 12–18 years, vaccine effectiveness of 2 doses of […]
The mRNA vaccines have been shown to be highly effective in preventing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and associated illness,1,2 although recent reports suggest reduced effectiveness against infection with the B.1.617.2 (or delta) variant.3,4 We assessed the effectiveness of the mRNA-1273 (Moderna) vaccine among incarcerated men during a coronavirus […]
Summary What is already known about this topic? Persons aged 12–18 years are eligible to receive COVID-19 vaccine. Currently, data are lacking on real-world vaccine effectiveness against COVID-19 hospitalization in adolescents. What is added by this report? Among hospitalized U.S. patients aged 12–18 years, vaccine effectiveness of 2 doses of […]
Background Vaccine effectiveness studies have not differentiated the effect of the delta (B.1.617.2) variant and potential waning immunity in observed reductions in effectiveness against SARS-CoV-2 infections. We aimed to evaluate overall and variant-specific effectiveness of BNT162b2 (tozinameran, Pfizer–BioNTech) against SARS-CoV-2 infections and COVID-19-related hospital admissions by time since vaccination among […]
In a national prospective cohort study involving 10.2 million participants in Chile, the effectiveness of an inactivated SARS-CoV-2 vaccine, which had been developed in China and administered in two doses 28 days apart, was estimated. Effectiveness among fully immunized persons was estimated at 65.9% for Covid-19 and at 87.5% for […]
