knowledge synthesis where certain steps of the systematic review process are omitted in order to be timely (e.g., quality assessment).4 On February 2, 2021, PHO Library Services conducted a literature search in MEDLINE, National Institutes of Health COVID-19 Portfolio (Preprints), Embase and Scopus. We searched Google on February 2, 2021 for additional articles of interest, including grey literature. English-language peer-reviewed and nonpeer-reviewed records that described the P.1 variant were included. Prior to posting, PHO subject-matter experts review all “What We Know So Far” documents. As the COVID-19 outbreak continues to evolve and the scientific evidence rapidly expands, the information provided in this document is only current as of the date of respective literature searches. It is important to note that the majority of the included papers were preprints. Results Epidemiology The first P.1 cases were identified in Japan among four travellers that arrived in Japan from Northern Brazil.5 It was subsequently traced back to Brazil5 where the P.1 lineage (previously known as B.1.1.28.1) was first confirmed to be in Brazil as early as December 4, 2020.3,6 As of February 2, 2021, P.1 has been confirmed in six countries with a total sequence count of 48 (Brazil [n=38], Japan [4], Italy [3], Faroe Islands [1], South Korea [1]), SA [1]. 6 The P.1 variant was first identified outside of Brazil in Japan on January 2, 2021, followed by the US (January 9, 2021), South Korea (January 10, 2021), Faroe Islands (January 12, 2021), and Italy (January 18, 2021).6 The first US case was identified in a resident of Minnesota with recent travel history to Brazil. 7 In Brazil, the variant has been detected in Rio de Janeiro, São Paulo, and now appears to be the dominant SARSCoV-2 strain in Manaus.8 Preliminary investigations conducted in Manaus, Amazonas State, demonstrate an increase in the proportion of cases sequenced as variant P.1, from 52.2% (35/67) in December 2020 to 85.4% (41/48) in January 2021. 9 COVID-19 P.1 Variant of Concern– What We Know So Far 3 Transmissibility While little is currently known about the transmissibility of the P.1 variant, Sabino et al. suggested that the P.1 variant identified in Manaus, Brazil may have higher transmissibility than pre-existing lineages. 10 They note a high frequency (42%, 13/31) of the P.1 lineage among samples sequenced from a cluster of COVID-19 cases in Manaus in December, 2020, but it was absent in 26 publicly-available genome surveillance samples collected in Manaus between March to November 2020. Additionally, the P.1 variant harbours the N501Y mutation that is found in the B.1.1.7 and B.1.351 variants, that has been associated with increased transmissibility. 10 The authors note that contact tracing and outbreak investigation data are needed to better understand relative transmissibility of this lineage. Disease Severity No research on the impact of the P.1 variant on disease severity was identified. Diagnostic Assays No research on the impact of the P.1 variant on diagnostic assays was identified. Since the P.1 variant does not contain any deletions in the S gene, it is unlikely to cause S gene target failures (e.g. S gene drop-out) that is known to occur with the B.1.1.7 variant. Vaccination While researchers are still investigating the effectiveness of vaccines against the P.1 variant Brazil,11 two pre-prints (not yet peer-reviewed) have tested plasma from recipients of both authorized mRNA vaccines against SARS-CoV-2 viruses with various spike mutations (i.e., variants of concern).12,13 • Wang et al. found that the B.1.351 variant showed resistance to neutralization by convalescent plasma (~11–33 fold) and vaccine sera (~6.5–8.6 fold), and that this was likely due to the E484K mutation, which is also present in P.1.12 They hypothesized that similar resistance to neutralizing plasma would be found in the P.1 lineage. • Similarly, Jangra et al. reported that polyclonal sera from vaccinated individuals and those previously infected with previous strains of SARS-CoV-2 had reduced neutralizing activity against the E484K mutation that is present in P.1. Additionally, they suggested that vaccinated individuals may be less protected against P.1, compared to the previous (USA-WA1/2020) strain.13 • Specifically, their in vitro study found that serum neutralization efficiency from individuals who received the Pfizer vaccine was lower against a SARS-CoV-2 strain that had the E484K mutation, compared to the USA-WA1/2020 strain. Human sera with high neutralization antibody titers against the USA-WA1/2020 strain were still able to neutralize the E484K SARS-CoV-2 strain. 13 However, neutralization efficiency of donor sera with low or moderate immunoglobulin G (IgG) against the SARS-CoV-2 spike protein had neutralization values similar to negative control samples against the E484K strain. This suggests that to enhance protection against newly emerging SARS-CoV-2 variants the highest vaccineinduced titers possible are needed. COVID-19 P.1 Variant of Concern– What We Know So Far 4 Immunity and Reinfection Since SARS-CoV-2 variants with the E484K mutation might be better at evading antibodies from the plasma of recovered COVID-19 patients infected with earlier strains, 13 the P.1 variant, containing this mutation, could increase the risk of re-infection or infection in vaccinated individuals. 14 Some