2/22—CDC: Fully vaccinated people do not need to quarantine after covid-19 exposure
CDC Says Fully Vaccinated People Do Not Need to Quarantine After COVID-19 Exposure—Here’s Why
[Media report.] Quarantining is recommended for people who have been exposed to COVID-19. Initially, this applied to anyone who has been exposed to COVID-19, except for people who had COVID-19 within the previous three months and show no symptoms. But now, the CDC has expanded those exceptions to include people who have been fully vaccinated against the disease within the last three months and show no symptoms. (FYI: "fully vaccinated" means at least two weeks have passed since the person got their second dose of a two-dose vaccine or one dose of a single-dose vaccine.) Infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, agrees with the change in guidance. "This corresponds with the guidance we give those who have recently recovered and have immunity," he says.
Serum Neutralizing Activity Elicited by mRNA-1273 Vaccine — Preliminary Report
The recent emergence of SARS-CoV-2 variants has led to concerns about potential to circumvent immunity elicited by natural infection or vaccination. We tested pseudoviruses bearing the spike protein from the original Wuhan-Hu-1 isolate, the D614G variant, the B.1.1.7 and B.1.351 variants, and other variants (20E [EU1], 20A.EU2, N439K-D614G, and the mink cluster 5 variant that was first identified in Denmark). Both the full panel of mutations in S and a subset of mutations affecting the receptor-binding domain (RBD) region of the B.1.1.7 variant had no significant effect. In contrast, we observed a decrease in titers of neutralizing antibodies against the B.1.351 variant and a subset of its mutations affecting the RBD. In serum samples obtained 1 week after the participants received the second dose of vaccine, we detected reductions by a factor of 2.7 in titers of neutralizing antibodies against the partial panel of mutations and by a factor of 6.4 against the full panel of mutations. However, in serum samples obtained from eight participants in the phase 1 trial, the geometric mean neutralizing titer against B.1.351 was 1:290, and all the serum samples neutralized the rVSV pseudovirus, albeit at relatively low dilutions. We observed a similar trend in serum samples obtained from macaque monkeys. Protection against the B.1.351 variant conferred by the mRNA-1273 vaccine remains to be determined.
Neutralizing Activity of BNT162b2-Elicited Serum — Preliminary Report
To analyze effects on neutralization elicited by BNT162b2, we engineered S mutations from the B.1.351 lineage into USA-WA1/2020, a relatively early isolate of the virus (in January 2020). We subsequently produced three recombinant viruses. All the serum samples neutralized USA-WA1/2020 and all mutant viruses at titers of 1:40 or greater. Geometric mean neutralizing titers against USA-WA1/2020, Δ242-244+D614G, B.1.351-RBD+D614G, and B.1.351-spike viruses were 501, 485, 331, and 184, respectively (Figure 1 and Table S1). Thus, as compared with neutralization of USA-WA1/2020, neutralization of Δ242-244+D614G virus was similar and neutralization of the B.1.351-spike virus was weaker by approximately two thirds.
SARS-CoV-2 testing for public health use: core principles and considerations for defined use settings
The development of rapid antigen tests, which can be used outside of the laboratory with fast turnaround times, has made widespread testing feasible. Although there were initial concerns about test performance, emerging evidence suggests that the most sensitive tests can detect 97% of infectious cases, based on the relationship between viral load and infectiousness. Moreover, modelling analyses show that frequency of testing and speed of reporting have a greater influence than test sensitivity on the effectiveness of SARS-CoV-2 infection surveillance.
Contact tracing in the context of COVID-19
[Updated WHO guidelines citing our preprint.] In scenarios where it may not be feasible to identify, monitor and quarantine all contacts, prioritization for follow-up should be given to contacts at a higher risk of infection based on their degree of exposure; and contacts at a higher risk of developing severe COVID-19. Ideally, contact tracers should be recruited from their own community and have an appropriate level of general literacy, strong communication skills, local language proficiency and an understanding of the local context and culture. Contact tracers should be informed on how to keep themselves safe.
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