their ongoing rapid test development programme using the innova rapid test, with increasing urgency as covid-19 cases increased across europe. on 6 november 2020, the prime minister, boris johnson, started city-wide screening of liverpool as part of the accelerated technology evaluation. further expansion of rapid tests pilots were also launched for many sectors where testing had not been previously available. these included students at universities who had been particularly hit by outbreaks. this initially started at durham university, who had the infrastructure and expertise to manage the rapid test programme, but was expanded to the majority of uk universities and enabled the national evacuation-style plan to get students safely home for christmas. rapid tests were also implemented within the national health service (nhs) for staff to reduce possible transmission to patients, local authorities and care homes to enable visits to visit residents. on 18 november 2020, wales completed the first whole borough testing at merthyr tydfil. global efforts to step up evaluations of rapid tests were initiated by the world health organization (who) emergencies department who launched a major rapid diagnostic test implementation project on the 10th of november 2020, aided by agreement from the bill and melinda gates foundation that limited costs for low- and middle-income countries. austria started country-wide mass testing on 5 december 2020 and ordered seven million tests consisting of the sd biosensor test and siemens clinitest (aka orientgene). by the middle of december 2020, there were many studies confirming the efficacy and success of using rapid tests to identify individuals with covid-19 including studies in the netherlands, the united kingdom, and the us. these studies all enabled rapid tests to enter standard national covid-19 testing strategies. global piloting of rapid tests was now common place in schools in canada, travel hubs in indonesia, and across india. in the us in december 2020, professor michael mina of harvard university noted that home tests were a "very powerful adjunct to everything else that people are already doing." this view was reinforced by professor william a. haseltine, also of harvard, in an article in forbes magazine asserting that "rapid, self-administered testing could stem the ever-surging tide of disease and death." however, further deployment of rapid tests as part of mass testing approaches in the us stalled as a result of the impasse around the $900 billion in covid-19 relief contained within the consolidated appropriations act, 2021. the bill was criticized for not specifically supporting covid rapid self-tests. meanwhile, the fda authorized the abbott binaxnow rat "for prescription use at home." subsequent approval was given for the first covid-19 at-home rat available without a prescription, by ellume. in the uk in december 2020, the medicines and healthcare products regulatory agency approved the innova rapid test for self-testing of asymptomatic people. the united kingdom's chief clinical medic, dr susan hopkins, noted that rapid tests provided a means to find "people that...we couldn't otherwise find". noting the ability to identify cases more rapidly, and considering the ensuing escalation in cases in europe, the european commission (ec) met in december 2020 and developed a common european framework for "use, validation and mutual recognition of rapid tests", committing 100 million euros for the purchase of tests from roche and abbott. stella kyriakides, commissioner for health and food safety, said "rapid antigen tests offer us speed, reliability and quick responses to isolate covid cases. this is crucial to slow down the spread of the pandemic." 2021 by january 2021, the council of the european union advocated greater use of rapid tests, noting that "should research prove that rapid antigen tests can be conducted by the testee themselves.... self-testing with or without professional guidance could also be considered." in the us, newly inaugurated us president joe biden released a national strategy for covid-19 that pledged to "fund rapid test acquisition and distribution for priority populations, work to spur development and manufacturing of at-home tests and work to ensure that tests are widely available." in march 2021, the us fda authorized the abbott binaxnow rat and the quidel quickvue rat for use at home without a prescription. innova voluntarily launched a class i recall in the us of more than 77,000 of its rats in april 2021. two months later, the fda warned americans to stop using the test because it had "significant concerns that the performance of the test has not been adequately established." a week after the fda's warning about the innova test, uk's medicines and healthcare products regulatory agency (mhra) cleared the rapid diagnostic's use and extended its authorization. in october 2021, who updated its interim guidance on ag-rdts. among other changes, the 2021 who interim guidance included updated information on test performance, uses selection, and storage. also in october 2021, ellume recalled more than 2.2 million of its home tests because of "higher-than-acceptable false positive test results for sars-cov-2". in december 2021, us president biden announced that the government planned to purchase and distribute for free 500 million at-home covid-19 rats. in response, dr leana wen was quoted as saying that the number of tests "does not come even close to what's needed." 2022 us president biden announced in january 2022 the purchase of 500 million additional rats for free distribution. in march 2022, who issued interim guidance on self-testing with ag-rdts. who made a strong recommendation that covid-19 ag-rdt self-testing "should be offered in addition to professionally administered testing services." an april 2022 warning from the us fda concerned two counterfeit at-home covid-19 rats. economic aspects costs and cost-effectiveness in late 2020, it was noted that in the us rats cost us$5-$23, in contrast with pcr tests which cost at least $75. in a danish study published in 2021, rats cost about $5.70 per test, as opposed to pcrs at $10.80 per test. a 2021 study from germany found that monitoring health care workers exposed to covid-19 with rats saves money compared with sending them into quarantine. a 2021 study concluded that if the us is willing to pay $100000 per year of life lost averted, then weekly or monthly testing of the population using rats is likely to be cost-effective. another 2021 study estimated incremental cost-effectiveness ratios of "$7890 per infection averted and $1 430 000 per death averted" if weekly screening with home-based rats were performed in the entire us population over a 60-day period. global market value estimates of value of the worldwide market for rats vary. one estimate was that the market size was $28 billion in 2021 with a compound annual growth rate (cagr) of -21.7%, leading to a size of $14 billion in 2028. a second estimate suggested that the market value was $4.6 billion in 2021, with a cagr of -26.3%, leading to a value of $743 million in 2027. a third estimate found a value of $5.3 billion in 2020, which was "anticipated to grow with a healthy growth rate of more than 6.7% over the forecast period 2021-2027."