travel measures in the sars cov 2 variant era need clear objectives CORD-Papers-2022-06-02 (Version 1)

Title: Travel measures in the SARS-CoV-2 variant era need clear objectives
Published: 2022-03-02
Journal: Lancet
DOI: 10.1016/s0140-6736(22)00366-x
DOI_URL: http://doi.org/10.1016/s0140-6736(22)00366-x
Author Name: Kucharski Adam J
Author link: https://covid19-data.nist.gov/pid/rest/local/author/kucharski_adam_j
Author Name: Jit Mark
Author link: https://covid19-data.nist.gov/pid/rest/local/author/jit_mark
Author Name: Logan James G
Author link: https://covid19-data.nist.gov/pid/rest/local/author/logan_james_g
Author Name: Cotten Matthew
Author link: https://covid19-data.nist.gov/pid/rest/local/author/cotten_matthew
Author Name: Clifford Samuel
Author link: https://covid19-data.nist.gov/pid/rest/local/author/clifford_samuel
Author Name: Quilty Billy J
Author link: https://covid19-data.nist.gov/pid/rest/local/author/quilty_billy_j
Author Name: Russell Timothy W
Author link: https://covid19-data.nist.gov/pid/rest/local/author/russell_timothy_w
Author Name: Peeling Rosanna W
Author link: https://covid19-data.nist.gov/pid/rest/local/author/peeling_rosanna_w
Author Name: Antonio Martin
Author link: https://covid19-data.nist.gov/pid/rest/local/author/antonio_martin
Author Name: Heymann David L
Author link: https://covid19-data.nist.gov/pid/rest/local/author/heymann_david_l
sha: a375bb8e5b92dbfff7b3b5cb64e115ba740dcea6
license: no-cc
license_url: [no creative commons license associated]
source_x: Elsevier; Medline; PMC; WHO
source_x_url: https://www.elsevier.com/https://www.medline.com/https://www.ncbi.nlm.nih.gov/pubmed/https://www.who.int/
pubmed_id: 35247312
pubmed_id_url: https://www.ncbi.nlm.nih.gov/pubmed/35247312
pmcid: PMC8890754
pmcid_url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8890754
url: https://doi.org/10.1016/s0140-6736(22)00366-x https://api.elsevier.com/content/article/pii/S014067362200366X https://www.ncbi.nlm.nih.gov/pubmed/35247312/ https://www.sciencedirect.com/science/article/pii/S014067362200366X
has_full_text: TRUE
Keywords Extracted from Text Content: pre-vaccine dogs test-to-release entirely-have UK epidemiology-ie UK Medical Research Council ( SARS-CoV-2 AJK dog COVID-19 B.1.1.529 travellers protocols-have
Extracted Text Content in Record: First 5000 Characters:The rapid global spread of new SARS-CoV-2 variants despite travel restrictions has revealed deficiencies in existing strategies and a need to evaluate them. 1 Such strategies-eg, vaccine passports, reactive flight bans, isolation of travellers who test positive for SARS-CoV-2 or blanket quarantines, and major changes to travel protocols-have often had weak accompanying justifications. Many governments continue to adapt various combinations of international travel measures and, increasingly, scale them back (figure) without stating clear objectives or the evidence behind them. In an era of SARS-CoV-2 variants and for future pandemic preparedness, there is a need for a transparent and evidence-based approach to travel strategies, supported by the development of clear international standards. In our view, there are several potential objectives that travel testing and restrictions can help address, including: monitoring incoming SARS-CoV-2 variants among travellers; reducing risk of outbreaks resulting from imported cases; delaying introduction and establishment of new variants of concern; and estimating SARS-CoV-2 prevalence in other countries to inform risk assessments. The choice of an objective for travel measures should depend on local and global prevalence of SARS-CoV-2 variants. When there is initially a low domestic prevalence of a particular variant, as occurred early in the COVID-19 pandemic, temporary travel restrictions can delay introductions 4 and could provide governments time to develop long-term strategies, such as reinforcing surveillance, contact tracing, public health measures, and vaccination campaigns. However, the marginal value of delaying importation of variants such as omicron (B.1.1.529) has declined in many countries because the speed of importations far exceeded the ability of most governments to implement reactive travel policies. Once variants are established locally, ongoing travel restrictions will have extremely limited impact on the local epidemic. 5 Furthermore, imposing travel restrictions on countries that discover and report new variants could be a disincentive to rapidly reporting findings, damaging a vital early warning system for the rest of the world. If the objective is to monitor importation of SARS-CoV-2 variants, full genome sequencing of incoming infections is typically required, but a lag in reporting data will hinder reactive travel measures. Given the costs and delays involved, targeted national genomic sampling would be more efficient if the objective is to identify variants of concern and provide early situational awareness to support local planning and response. 6 Although SARS-CoV-2 testing can help identify infections, quarantine has been used in many countries to reduce risks of onward transmission from incoming travellers with unknown or uncertain infection status. Quarantine is unable to fully prevent local transmission; 7 stringent domestic restrictions were required to contain subsequent outbreaks in the pre-vaccine era, and containment has become harder with more transmissible variants. Stringent quarantine for all travellers also comes with substantial individual and societal costs. However, such costs may be mitigated through the use of testing after arrival, with test-to-release schemes decreasing the time required for quarantine. 8 Given the volume of indirect connections in the global flight network, efforts to merely delay introductionsrather than prevent them entirely-have limited value unless the aim is simply to delay spread by a few days, or if the delay is supplemented by additional domestic measures. In the face of new variants, a less economically disruptive alternative to outright travel bans is to use arrival SARS-CoV-2 testing, as many countries require. Although rapid antigen tests are less sensitive than PCR tests in detecting infection, most have high sensitivity for detecting individuals at the point they are likely to transmit infection. 9 Modelling studies have estimated that repeat rapid antigen tests are more likely to detect active infection than less frequent PCR tests, which are often associated with slower results and higher costs. 10 Daily testing of individuals considered a potential transmission risk with rapid antigen tests might also feasibly replace home quarantine with no expected increase in onwards transmission. 11 Another potential approach might include trained dogs that distinguish between infected and uninfected individuals using odour samples. 12, 13 An advantage of this approach would be its speed and the fact that a laboratory specimen or test kit is not required; dogs can potentially screen up to 250 travellers per hour per dog, and trials are underway in the UK. 14 However, more evidence is needed before such an approach could be routinely implemented. Alongside testing, COVID-19 vaccination certification has increasingly been used in international travel requirements, and in some cases as a substitute fo
Keywords Extracted from PMC Text: epidemic.5 quarantine.8 costs.10 pre-vaccine introductions4 UK.14 transmission;7 COVID-19 effective,15 travellers test-to-release dog dogs SARS-CoV-2 transmission.11 countries,16 samples.12 infection.9
Extracted PMC Text Content in Record: First 5000 Characters:The rapid global spread of new SARS-CoV-2 variants despite travel restrictions has revealed deficiencies in existing strategies and a need to evaluate them.1 Such strategies—eg, vaccine passports, reactive flight bans, isolation of travellers who test positive for SARS-CoV-2 or blanket quarantines, and major changes to travel protocols—have often had weak accompanying justifications. Many governments continue to adapt various combinations of international travel measures and, increasingly, scale them back (figure ) without stating clear objectives or the evidence behind them. In an era of SARS-CoV-2 variants and for future pandemic preparedness, there is a need for a transparent and evidence-based approach to travel strategies, supported by the development of clear international standards. In our view, there are several potential objectives that travel testing and restrictions can help address, including: monitoring incoming SARS-CoV-2 variants among travellers; reducing risk of outbreaks resulting from imported cases; delaying introduction and establishment of new variants of concern; and estimating SARS-CoV-2 prevalence in other countries to inform risk assessments. The choice of an objective for travel measures should depend on local and global prevalence of SARS-CoV-2 variants. When there is initially a low domestic prevalence of a particular variant, as occurred early in the COVID-19 pandemic, temporary travel restrictions can delay introductions4 and could provide governments time to develop long-term strategies, such as reinforcing surveillance, contact tracing, public health measures, and vaccination campaigns. However, the marginal value of delaying importation of variants such as omicron (B.1.1.529) has declined in many countries because the speed of importations far exceeded the ability of most governments to implement reactive travel policies. Once variants are established locally, ongoing travel restrictions will have extremely limited impact on the local epidemic.5 Furthermore, imposing travel restrictions on countries that discover and report new variants could be a disincentive to rapidly reporting findings, damaging a vital early warning system for the rest of the world. If the objective is to monitor importation of SARS-CoV-2 variants, full genome sequencing of incoming infections is typically required, but a lag in reporting data will hinder reactive travel measures. Given the costs and delays involved, targeted national genomic sampling would be more efficient if the objective is to identify variants of concern and provide early situational awareness to support local planning and response.6 Although SARS-CoV-2 testing can help identify infections, quarantine has been used in many countries to reduce risks of onward transmission from incoming travellers with unknown or uncertain infection status. Quarantine is unable to fully prevent local transmission;7 stringent domestic restrictions were required to contain subsequent outbreaks in the pre-vaccine era, and containment has become harder with more transmissible variants. Stringent quarantine for all travellers also comes with substantial individual and societal costs. However, such costs may be mitigated through the use of testing after arrival, with test-to-release schemes decreasing the time required for quarantine.8 Given the volume of indirect connections in the global flight network, efforts to merely delay introductions—rather than prevent them entirely—have limited value unless the aim is simply to delay spread by a few days, or if the delay is supplemented by additional domestic measures. In the face of new variants, a less economically disruptive alternative to outright travel bans is to use arrival SARS-CoV-2 testing, as many countries require. Although rapid antigen tests are less sensitive than PCR tests in detecting infection, most have high sensitivity for detecting individuals at the point they are likely to transmit infection.9 Modelling studies have estimated that repeat rapid antigen tests are more likely to detect active infection than less frequent PCR tests, which are often associated with slower results and higher costs.10 Daily testing of individuals considered a potential transmission risk with rapid antigen tests might also feasibly replace home quarantine with no expected increase in onwards transmission.11 Another potential approach might include trained dogs that distinguish between infected and uninfected individuals using odour samples.12, 13 An advantage of this approach would be its speed and the fact that a laboratory specimen or test kit is not required; dogs can potentially screen up to 250 travellers per hour per dog, and trials are underway in the UK.14 However, more evidence is needed before such an approach could be routinely implemented. Alongside testing, COVID-19 vaccination certification has increasingly been used in international travel requirements, and in some cases as a substitute for more
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