Covid vaccines - thread banned users in First Post

People who are fully vaccinated and people who are unvaccinated may behave differently, particularly with regard to social interactions and therefore may have differing levels of exposure to COVID-19.

. The number of confirmed cases is likely to be an underestimate of the total number who have, or have had, COVID-19. A person can have multiple tests but will only ever be counted once. The drop in the number of confirmed cases at weekends likely reflects that laboratories are doing fewer tests at the weekend. On 05 January 2022, the Scottish Government announced that asymptomatic people who return a positive lateral flow test (LFT) would no longer have to confirm their positive result with a PCR test.

More recently, however, the monthly proportion of reinfections has risen to 6.4% in December 2021 and 9.8% in January 2022, coinciding with a rapid increase of the Omicron variant in Scotland. Evidence suggests that the Omicron variant is associated with increased risk of reinfection3. 

On 05 January 2022, the Scottish Government announced that people who do not have symptoms would no longer be asked to take a polymerase chain reaction (PCR) test to confirm a positive Lateral Flow Device (LFD) result. Instead, anyone with a positive LFD, who does not have symptoms, should report the result online as soon as the test is done. In order to ensure that we continue to provide the most accurate information, changes have been made to the national COVID-19 case definition to reflect this revised testing strategy. 

Scotland’s approach to contact tracing has continued to adapt throughout the pandemic to reflect changing circumstances, variability in cases, and increasing proportion of the population fully vaccinated since the roll out of the vaccination programme. The most recent Strategic Framework issued by the Scottish Government in November 2021 sets out how Scotland will continue to adapt now that we are in the phase described as “beyond level zero”

There is a large risk of misinterpretation of the data presented in this section due to the complexities of vaccination data. A blog post by the UK Health Security Agency (UKHSA), formerly Public Health England (PHE), provides a comprehensive explanation of the biases and potential areas for misinterpretation of such data. They state that a simple comparison of COVID-19 case rates in those who are vaccinated and unvaccinated should not be used to assess how effective a vaccine is in preventing serious health outcomes, because there are a number of differences between the groups, other than the vaccine itself, and these biases mean that you cannot use the rates to determine how well the vaccines work.

Data and rates presented in this section are not a measure of vaccine effectiveness Vaccine effectiveness is a scientific method used to measure how well a vaccine protects people against outcomes such as infection, symptoms, hospitalisation and death in the ‘realworld’. Unlike case rates, vaccine effectiveness analysis accounts for potential biases in the data and risk factors such as age, sex, prior infection, co-morbidities, socio-economic status, and time since vaccination. This method is the most robust way to measure if a vaccine is working. The data and rates presented in this section do not account for biases and risk factors and should not be used to measure vaccine effectiveness. We include links to vaccine effectiveness studies below.

There are likely to be systematic differences and biases between the vaccinated and unvaccinated groups, such as behaviour, vulnerability and previous infection that are unaccounted for when comparing rates. As most of the population is vaccinated, these differences become more evident and could create bias in case/hospitalisation/death rates between vaccinated and unvaccinated population. For example, people who are vaccinated may be more likely to have health seeking behaviour and follow other government guidance such as regular testing and reporting for COVID-19, which makes them more likely to be identified as a case than unvaccinated people, resulting in higher case rates in the vaccinated population.

For example, some of the older individuals who have exceeded the recommended time will have not received their next vaccine dose because of frailty or ill health. They are, therefore, more likely to be hospitalised or die if they get COVID-19.

UKHSA publish a summary of current vaccine effectiveness in their weekly COVID-19 vaccine surveillance report. The latest evidence can be found below which suggests the COVID-19 booster/third dose vaccine lowers your risk of a severe outcome compared to the second dose.

Case rates have declined and subsequently plateaued in the last three weeks from 08 January 2022 to 28 January 2022. Caution should be taken when interpreting recent case trends due to the change in policy from 06 January 2022 where an asymptomatic individual who tests positive via a LFD test is not required to take a confirmatory PCR test. This section of the report only includes PCR confirmed COVID-19 cases and does not include cases confirmed by a LFD test.

In the last week from 22 January 2022 to 28 January 2022, in an age-standardised population, the rate of COVID-19 related acute hospital admissions in individuals that received a booster or third dose of a COVID-19 vaccine was between 3.4 to 4.0 times lower than in individuals who are unvaccinated or have only received one or two doses of a COVID-19 vaccine. 

Analyses from Scotland show that the booster and third dose of the COVID-19 vaccines are associated with 57% reduced risk of symptomatic infection with the Omicron variant compared to those who are more than 25 weeks post-second dose of COVID-19 vaccine.

The number of PCR confirmed COVID-19 cases and case rates have declined in the last week from 21 January 2022 to 28 January 2022. Caution should be taken when interpreting recent case trends due to the change in policy from 06 January 2022 where an asymptomatic individual who tests positive via a LFD test is not required to take a confirmatory PCR test.