Darllenwch y dudalen hon yn Cymraeg

After what has been a difficult year, the vaccination roll-out will no doubt be a ray of hope for many. This brings with it a huge amount of interest in the progress of the roll-out, with many people wanting to know when they or their loved ones might receive their vaccination (if they haven’t already). In this blog, written jointly by epidemiologists in Public Health Wales and statisticians in the Welsh Government, we want to set out what you can expect to see from vaccination data over the coming weeks and months.

Statistics on people vaccinated

Public Health Wales has a long-standing role in vaccination surveillance, with responsibility for monitoring uptake of all routine adult and childhood vaccination programmes. The well-established surveillance methods used for these programmes have been extended to surveillance of the COVID-19 programme.

Back in December Public Health Wales began publishing weekly data on the number of people receiving a COVID-19 vaccination. Since then, both the frequency and depth of vaccination data has expanded, with all of it available through the COVID-19 surveillance dashboard. Early in January Public Health Wales made the move to publishing daily vaccination data and this now includes daily information on a number of the priority vaccination groups, such as the over 80s and care home residents. On a weekly basis, the coverage figures are also published down to health board level.

This is still just the start. Over time more data will be added for the other vaccination prioritisation categories recommended by the Joint Committee on Vaccination and Immunisation (JCVI).

• During February, the surveillance reports will be expanded to cover all of the 9 priority groups recommended by the JCVI.
• On a monthly basis, from February, surveillance reports will include information on equity of coverage between ethnic groups and level of socioeconomic deprivation. Over time this will be expanded to look at coverage at a geographical level too.
• Public Health Wales are also conducting surveillance studies of vaccination effectiveness, which involves linking a number of national surveillance datasets. One of these studies is a national cohort study, developed in collaboration with Swansea University.

Calculating vaccine uptake

In Wales, COVID-19 vaccination data comes from the Welsh Immunisation System (WIS), a new system developed and rolled out by the NHS Wales Informatics Service (NWIS) specifically to manage the delivery of COVID-19 vaccinations. The system schedules appointments and keeps track of when vaccinations have taken place, as well as providing us with a rich source of data. WIS provides all the data needed to calculate vaccine uptake.

As well as telling us how many people have received a vaccination, WIS also includes data on the overall size and characteristics of the population so that we can work out the percentage of people who have had a vaccination. This is known as the population coverage of vaccination. This coverage figure is based on the number of people resident in Wales and registered with a GP. People are included in the per cent coverage calculation even if they can’t have a vaccine or have chosen not to have it.

There are a number of ways of calculating the percent of people vaccinated, but this approach used by PHW is the standard public health method for measuring vaccination surveillance and is international good practice. However it does have some limitations. GP registers might not accurately capture the number of people in some groups, for example younger men who can be slower to update their GP records if they move. Records for other groups, such as health care workers, need to be carefully scrutinised by health boards to make sure they capture robust information.

Each part of the UK is developing its vaccination statistics at speed and sometimes our methods can differ. We’ll keep working with our colleagues across the 4 nations to help users compare and explain the different sets of data.

Other statistics on the vaccination programme

Whilst Public Health Wales has focused its analysis on people being vaccinated, statisticians in the Welsh Government have focused on providing regular data on the more operational aspects of the vaccination roll-out. We now publish a weekly report on vaccines that couldn’t be used, sometimes referred to as “wastage”. People often ask how many vaccine doses Wales has been allocated, so we want to expand this weekly publication to include data on vaccine supplies too. As this data has the potential to be commercially sensitive, we are working with colleagues across the UK to find ways of sharing this information in a safe way.

There are more areas that we’d like to explore in future, such as:

• Where was a vaccine administered, for example at a GP surgery, vaccination centre or pharmacy?
• How many people refused or did not attend a vaccine appointment?

In some cases, this data is not easily available from WIS. We’re continuing to explore what sources are available to help answer these questions and more.

A word on data quality

Vaccinations is another example of using “management information” to produce statistics. This is something we’ve become very used to over the course of the pandemic, with management information on testing, people in hospital, contact tracing and more all featuring heavily in public debate. The previous Chief Statistician wrote about the importance of recognising that the quality of management information might be different to what we’d expect from more regular official statistics. He wrote:

Our job as government statisticians is to do as much as we can to explain clearly and openly the limitations of those data, and to be transparent to users when we identify issues.

These are principles we’re applying to the world of vaccination data too.

As with all administrative systems, the main purpose of WIS isn’t to report statistics. However, epidemiologists in Public Health Wales have worked with specialist teams in NWIS to ensure that the system is capable of providing essential data for vaccination surveillance. WIS is being developed and improved as the vaccination programme is expanded and the Public Health Wales surveillance team is working with NWIS, health boards and other NHS organisations, to understand the data within WIS, quality assuring and improving where appropriate. This is why the range of data that’s published on vaccinations is gradually expanding, as we become more confident in the information that’s available.

Whilst WIS is a rich source of data, it might not give us the answer to all questions on vaccination. We’ll also be looking at how we can use other sources such as data linkage, working with ONS on what we can learn from the COVID-19 infection survey, and using surveys to collect further information on attitudes to vaccination. For example, the fortnightly Public Health Wales survey How are we doing in Wales? has already provided some important insight on this topic.

Public interest in vaccination data is already very high and growing day by day. As we’ve seen with testing and hospital data during the pandemic, we know the most pressing topics will evolve over time and new areas will emerge. We are always keen to hear how you use our data and what you need to know about, so please get in touch.

Stephanie Howarth, Chief Statistician, Welsh Government
Simon Cottrell, Senior Principal Epidemiologist, Public Health Wales

Email: stats.info.desk@gov.wales