COVID-19: Changing testing requirements and reducing the self-­isolation period

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As of 21 January 2022, the world has been living with the COVID-19 pandemic for nearly two years. The introduction of vaccinations beginning in the UK on 8 December 2020 and the use of lateral flow tests (LFTs), polymerase chain reaction (PCR) tests and self­-isolation following a positive test result have gone some way to help in the global fight against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19. In this article, we will consider the most recent updates to the rules and guidance on self-­isolation and testing surrounding SARS-CoV-2 in the UK and the science behind these changes.

Since the introduction of testing for SARS-CoV-2 on 18 May 2020, within the UK there has been a requirement to self-­isolate on receipt of a positive test result [1]. Compliance with this requirement has been consistently high; approximately three-quarters of all positive individuals fully complied with the mandated 10 days of self­-isolation during selected periods of study in July, September, November and December 2021 [2], and there is little doubt that self­-isolation has helped to control cases of COVID-19 in the community.
However, there have long been concerns within the UK that essential public services and supply chains could be affected if enough individuals in the population were to become infected [3]. Unfortunately, these concerns were realised with the arrival to the UK of the latest, highly infectious SARS-CoV-2 variant (Omicron) in November 2021 [4]. Vast numbers of individuals were infected with the virus and were therefore required to self­-isolate [5]. This led to widespread social and economic disruption, which prompted the publication of new guidance on self­-isolation from the UK Health Security Agency (UKHSA) from 22 December 2021 [6]. The aim of this guidance was to reduce disruption by decreasing the self­-isolation period of 10 days to 7 days regardless of an individual’s vaccination status, providing that they tested negative on two LFTs taken 24 hours apart on Days 6 and 7 of the isolation period [6]. (A lack of symptoms and two consecutive negative tests as described imply that the SARS-CoV-2 viral proteins are no longer being shed by the individual [7]). Individuals ending their period of self­-isolation before 10 days were advised to work from home, socially distance in poorly ventilated or crowded areas, and limit contact with those particularly vulnerable to severe disease as a result of SARS-CoV-2 infection for up to 10 full days from the start of their self­-isolation period [6].

In December 2021, the USA took reductions to the self­-isolation period one step further, with the Centers for Disease Control and Prevention (CDC) recommending a 5-day isolation period, providing that individuals with COVID-19 show resolving or no symptoms [8]. According to the CDC, this change was based on data showing that most transmissions of the Omicron variant of SARS CoV-2 occur 1–2 days pre- and 2–3 days post-symptom onset [8,9]. As of 17 January 2022, the self­-isolation period was also reduced to 5 days in England, providing that the individual tested negative on two LFTs taken 24 hours apart on Days 5 and 6 of the isolation period [10].

Additionally, as of 11 January 2022, the UKHSA eased testing rules, meaning that asymptomatic individuals are no longer required to confirm a positive LFT result with a positive result from a PCR test, although they are still required to self­-isolate in line with the guidance outlined above [11]. PCR tests detect viral genetic material, whereas LFTs detect viral proteins, which are present when an individual is infectious [7]. PCR tests are more effective than LFTs at detecting SARS-CoV-2 because they replicate the viral genetic material, which subsequently enables minute amounts to be detected; however, LFTs do not use this process, so they may miss cases with low viral levels [7]. However, the high positive predictive value of an LFT when there is a very high virus prevalence means that LFTs are sufficient for testing purposes [11]. This means that a positive LFT is much more likely to accurately indicate that an individual is infected with SARS-CoV-2 now than it did in the summer of 2021 – the effectiveness of the tests has not changed, but as there are more cases in the population to be detected, the number of ‘true positives’ will be higher [11,12]. Thus, the PCR test currently adds little extra value compared with LFTs and compared with when prevalence rates were much lower than current levels [12]. The use of LFTs alone will also help to mitigate the concern surrounding individuals with a positive LFT who don’t self-isolate while waiting for their PCR test result to be returned and who could therefore be potentially transmitting the virus in this time [11].

Therefore, from the above, it is apparent that the rules around COVID-19 testing and self­-isolation will require constant adaptation as the pandemic continues and more data are collected. As we continue to live in a world where COVID-19 is still very much a part of our existence, we are constantly having to find ways to balance public health and safety with the psychosocial, economic and educational needs of the community. Hopefully, the accumulation of data over time will help to inform the best strategy to achieve this and pave the way to a healthier future.

Disclaimer: This article is not a substitute for medical advice. The rules and guidance on self­-isolation and testing surrounding SARS-CoV-2 in the UK is constantly changing. Please check trusted resources such as GOV.UK for the latest updates.

1. GOV.UK. Everyone in the United Kingdom with symptoms now eligible for coronavirus tests. Available at: Accessed January 2022.
2. Office for National Statistics. Coronavirus and self­-isolation after testing positive in England: 29 November to 4 December 2021. Available at: Accessed January 2022.
3. Mahase E. Covid-19: Is it safe to reduce the self­-isolation period? BMJ 2021; 375: n3164.
4. BBC News. Covid: New variant classed ‘of concern’ and named Omicron. Available at: Accessed January 2022.
5. GOV.UK. Government takes action to mitigate workforce disruption. Available at: Accessed January 2022.
6. Limb M. Covid-19: Self­-isolation after infection cut to seven days in England. BMJ 2021; 375: n3137.
7. NewScientist. How reliable are covid-19 lateral flow tests for detecting omicron? Available at: Accessed January 2022.
8. Tanne JH. Covid-19: CDC shortens isolation period as US cases hit record high. BMJ 2021; 375: n3161.
9. Centers for Disease Control and Prevention. CDC updates and shortens recommended isolation and quarantine period for general population. Available at: Accessed January 2022.
10. BBC News. Covid self­-isolation in England being cut to five full days. Available at: Accessed January 2022.
11. BBC News. Covid: PCR not needed after positive lateral flow under new plans. Available at: Accessed January 2022.
12. BBC News. Why are lateral flows better now? Available at: Accessed January 2022.

Author: Beth Wynne-Evans, Part 1 FRCPath, MBBS, PGCE, BSc
Medical Advisor and Senior Medical Writer | Porterhouse Medical