Brief : COVID-19 Vaccines and Vaccination

Abstract

All COVID-19 vaccines currently approved or authorized in the United States (P zer-BioNTech/Comirnaty, Moderna, and Janssen [Johnson & Johnson]) are e ective against COVID-19, including against severe disease, hospitalization, and death. Available evidence suggests the currently approved or authorized COVID-19 vaccines are highly e ective against hospitalization and death for a variety of strains, including Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), and Delta (B.1.617.2); data suggest lower e ectiveness against con rmed infection and symptomatic disease caused by the Beta, Gamma, and Delta variants compared with the ancestral strain and Alpha variant. Ongoing monitoring of vaccine e ectiveness against variants is needed. Limited available data suggest lower vaccine e ectiveness against COVID-19 illness and hospitalization among immunocompromised people. In addition, numerous studies have shown reduced immunologic response to COVID-19 vaccination among people with various immunocompromising conditions. The risk for SARS-CoV-2 infection in fully vaccinated people cannot be completely eliminated as long as there is continued community transmission of the virus. Early data suggest infections in fully vaccinated persons are more commonly observed with the Delta variant than with other SARS-CoV-2 variants However data show fully vaccinated Data were added indicating that COVID-19 vaccination remains highly e ective against COVID-19 hospitalization and death caused by the Delta variant of SARS-CoV-2. Data were added from studies published since the last update that further characterize reduced COVID-19 vaccine e ectiveness against asymptomatic and mild symptomatic infections with the Delta variant of SARS-CoV2. Data were added from studies published since the last update that suggest decreased vaccine e ectiveness against SARS-CoV-2 infection, symptomatic disease, and hospitalization in several groups of immunocompromised persons and potential bene t of a third dose of COVID-19 vaccine in immunocompromised populations. Data were added summarizing several small studies of heterologous COVID-19 vaccination series (i.e., mixed schedules), which found that a dose of adenovirus vector vaccine followed by a dose of mRNA vaccine elicits antibody responses at least as high as two doses of mRNA vaccine. Data were added from recent studies examining the duration of protection conferred by COVID-19 vaccination. Data were added from recent studies describing clinical outcomes and transmissibility of SARS-CoV-2 infections in fully vaccinated persons.