Public Accountability Unit
T 020 8327 6920
133-155 Waterloo Road
London SE1 8UG
Our ref: 09/03/tr/3000
07 April 2021
Dear Meric Kesic, Re: Vaccination data among health care workers
Thank you for your request received on 09 March 2021 addressed to Public Health
England (PHE). In accordance with Section 1(1)(a) of the Freedom of Information
Act 2000 (the Act), I can confirm that PHE does hold some of the information you
have specified. I have responded to your requests in the order raised:-
1) What information have you got on the pcr tests ability to know the
difference between covid19 and any other coronavirus?
A range of different PCR assays are being used by Public Health England for the
detection of the Covid-19 virus. The specificity of each test is carefully evaluated
including the ability to detect the Covid-19 virus (including variants) and to
distinguish these from other coronaviruses. The specificities of the assays used are
available from the individual manufacturers who are responsible for their production.
Evaluations are also available in the peer reviewed scientific literature including that
originally produced by an international scientific consortia which included staff from
PHE and is available from the reference given below:
Corman VM, Landt O, Kaiser M, Molenkamp R, Meijer A, Chu DK, Bleicker T,
Brünink S, Schneider J, Schmidt ML, Mulders DG, Haagmans BL, van der Veer B,
van den Brink S, Wijsman L, Goderski G, Romette JL, Ellis J, Zambon M, Peiris M,
Goossens H, Reusken C, Koopmans MP, Drosten C. Detection of 2019 novel
coronavirus (2019-nCoV) by real-time RT-PCR. Euro Surveill. 2020
Jan;25(3):2000045. doi: 10.2807/1560-7917.ES.2020.25.3.2000045. Erratum in:
Euro Surveill. 2020 Apr;25(14): Erratum in: Euro Surveill. 2020 Jul;25(30): PMID:
31992387; PMCID: PMC6988269.
2) What information have you got on why you test for coronavirus (flu and
common cold) and not covid19?
Public Health England performs a very wide range of tests for human pathogens
including viruses transmitted via the respiratory tract (influenza, covid-19 and other
coronaviruses). Data is published through periodic surveillance updates on the PHE
website and in specific studies. Two examples of specific studies are given in the
Beale S, Lewer D, Aldridge RW, Johnson AM, Zambon M, Hayward A, Fragaszy E.
Household transmission of seasonal coronavirus infections: Results from the Flu
Watch cohort study. Wellcome Open Res. 2020 Jun 19;5:145. doi:
10.12688/wellcomeopenres.16055.1. PMID: 33553677; PMCID: PMC7848853.
Aldridge RW, Lewer D, Beale S, Johnson AM, Zambon M, Hayward AC, Fragaszy
EB; Flu Watch Group. Seasonality and immunity to laboratory-confirmed seasonal
coronaviruses (HCoV-NL63, HCoV-OC43, and HCoV-229E): results from the Flu
Watch cohort study. Wellcome Open Res. 2020 Dec 10;5:52. doi:
10.12688/wellcomeopenres.15812.2. PMID: 33447664; PMCID: PMC7786426.
3) What information have you got about the false positive rates for the pcr
No diagnostic test is 100% accurate, false positives and false negatives can occur
depending on a number of factors not directly related to the test performance. Once
in use, the performance of the test is continually monitored and reviewed for
technical quality and performance. PHE is very aware of the risk of false positives
where prevalence is low in the population being tested and is working with all Pillar 1
and Pillar 2 labs to put in place measures to reduce that risk including ensuring that
appropriate CT values are being used and that where appropriate samples are re-
tested to ensure results are as accurate as possible. Further information can be
found through the following link - https://www.gov.uk/government/publications/sars-
Daily reported case numbers exclude results that have been identified as false.
In June 2020 the Scientific Advisory Group for Emergencies published a briefing
paper on the impact of false positives and false negatives in the United Kingdom’s
COVID-19 reverse transcription polymerase chain reaction (RT-PCR) testing
The briefing paper states that the United Kingdom operational false positive rate is
unknown, and an attempt has been made to estimate the likely false-positive rate of
national COVID-19 testing programmes by examining data from published external
quality assessments (EQAs) for RT-PCR assays for other ribonucleic acid viruses
carried out between 2004-2019. Results of 43 EQAs were examined, giving a
median false positive rate of 2.3%. The paper can be accessed here: https://www.gov.uk/government/publications/gos-impact-of-false-positives-
4) What information have you got about the cycle rate of the pcr
The Cycle Threshold varies between the various platforms used within each testing
laboratory, and is not therefore uniform. There is correlation between some Platform
types, where all parts of the process are similar. Every PHE laboratory has
determined the limit of detection for SARS-CoV-2 across all assays used for patient
testing. Additionally, every PHE laboratory has in place a strategy for the
confirmation of positive results when the screening result was above the threshold
identified in the screening assays.
PHE does not hold this information for non-PHE laboratories. Many laboratories
contribute to the government’s testing programme and PHE does not maintain
central records of testing undertaken in each lab.
Under Section 16 of the FOI Act, public authorities have a duty to provide advice and
assistance. Accordingly, you may wish to contact the Department of Health and
Social Care, which may be able to advise further. The contact details can be found
If you have any queries regarding the information that has been supplied to you,
please refer your query to me in writing in the first instance. If you remain dissatisfied
and would like to request an internal review, then please contact us at the address
above or by emailing firstname.lastname@example.org.
Please note that you have the right to an independent review by the Information
Commissioner’s Office if a complaint cannot be resolved through the PHE
complaints procedure. The Information Commissioner’s Office can be contacted by
calling the ICO’s helpline on 0303 123 1113, visiting the ICO’s website at www.ico.org.uk
or writing to the ICO at Wycliffe House, Water Lane, Wilmslow,
Cheshire, SK9 5AF.