- All COVID-19 vaccines currently authorized in the United States are effective against COVID-19, including serious outcomes of severe disease, hospitalization, and death.
- Available evidence suggests the currently authorized mRNA COVID-19 vaccines (Pfizer-BioNTech and Moderna) are highly effective 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 effectiveness against confirmed infection and symptomatic disease caused by the Beta, Gamma, and Delta variants compared with the ancestral strain and Alpha variant. Ongoing monitoring of vaccine effectiveness against variants is needed.
- A growing body of evidence indicates that people fully vaccinated with an mRNA vaccine (Pfizer-BioNTech or Moderna) are less likely than unvaccinated persons to acquire SARS-CoV-2 or to transmit it to others. However, the risk for SARS-CoV-2 breakthrough infection in fully vaccinated people cannot be completely eliminated as long as there is continued community transmission of the virus.
- Studies are underway to learn more about the effectiveness of Johnson & Johnson/Janssen vaccine.
- At this time, there are limited data on vaccine effectiveness in people who are immunocompromised. People with immunocompromising conditions, including those taking immunosuppressive medications, should discuss the need for personal protective measures after vaccination with their healthcare provider.
- This updated science brief synthesizes the scientific evidence supporting CDC’s guidance for fully vaccinated people and will continue to be updated as more information becomes available.
COVID-19 vaccination is a critical prevention measure to help end the COVID-19 pandemic. COVID-19 vaccines are now widely available in the United States, and CDC recommends all people 12 years and older be vaccinated against COVID-19. Three COVID-19 vaccines are currently authorized by the U.S. Food and Drug Administration (FDA) for emergency use: two mRNA vaccines (Pfizer-BioNTech, Moderna) and one adenoviral vector vaccine (Johnson & Johnson/Janssen vaccine). People are considered fully vaccinated if they are ≥2 weeks following receipt of the second dose in a 2-dose series (mRNA vaccines), or ≥2 weeks following receipt of a single-dose vaccine (Johnson & Johnson/Janssen).*
Public health recommendations for people fully vaccinated with authorized COVID-19 vaccines must consider evidence of vaccine effectiveness against symptomatic and asymptomatic COVID-19, as well as vaccine impact on SARS-CoV-2 transmission. Other individual and societal factors are also important when evaluating the benefits and potential harms of additional prevention measures among vaccinated individuals. The Advisory Committee on Immunization Practices and CDC routinely consider factors such as population values, acceptability, and feasibility of implementation when making vaccine recommendations.1 These factors were also considered when developing CDC’s interim public health recommendations for fully vaccinated people.
In this scientific brief, we summarize evidence available through July 24, 2021, for the currently authorized COVID-19 vaccines (administered according to the recommended schedules) and additional considerations used to inform public health recommendations for fully vaccinated people, including:
- Vaccine efficacy and effectiveness against SARS-CoV-2 infection
- Vaccine performance against emerging SARS-CoV-2 variant viruses
- Impact of other prevention measures in the context of vaccination
Accumulating evidence indicates that fully vaccinated people without immunocompromising conditions are able to engage in most activities with low risk of acquiring or transmitting SARS-CoV-2. The benefits of avoiding disruptions such as unnecessary quarantine and social isolation might outweigh the low residual risk of becoming ill with COVID-19, generally with mild disease.
Vaccine effectiveness in immunosuppressed people
Evidence of reduced antibody response to or reduced immunogenicity of COVID-19 mRNA vaccination has been observed in the following groups: people taking certain immunosuppressive medications like rituximab (47-50) or mycophenolate (50-53), people with hematologic cancers (54, 55), and hemodialysis patients (56). At this time, data on vaccine protection in people who are immunocompromised are limited; in addition, the impact of immune suppression on COVID-19 vaccine effectiveness may vary by condition.(55, 57) Complete data on which immunocompromising conditions might affect response to COVID-19 vaccination are not available; in addition, there is no established immune correlate of protection against SARS-CoV-2 so the risk of infection in people who respond incompletely to COVID-19 vaccination cannot be quantified using immunogenicity data. People with immunocompromising conditions, including those taking immunosuppressive medications, should discuss the need for personal protective measures after vaccination with their healthcare provider.
Vaccine-induced neutralizing antibody activity
Two studies have shown that six months after receiving the Moderna vaccine, higher proportions of people had undetectable neutralization activity against Beta and Gamma compared with the ancestral strain.(130, 131)
Vaccine-induced cellular immunity
Several studies have assessed CD4+ and CD8+ T cell responses from Moderna or Pfizer vaccine recipients to the ancestral SARS-CoV-2 strain compared with the Alpha, Beta, Gamma, and Epsilon variants; these studies observed modest or no defects in cellular immune recognition of the variants.(78, 85, 105, 135-139)
https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/fully-vaccinated-people.html
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