Registration for the UK Flu Survey began in mid-July. We now have over 5500 registered users from all over the UK. The locations of recent participants are shown in the map on the right. Those whose symptoms are consistent with Influenza are shown in red and those without respiratory symptoms are shown in green. Because users only record the first half of their postcode, points on the map do not indicate user's households. Click here to see an interactive map of the UK results so far (may be slow to load). Click here to plot your own results

Holidays and contact patterns

Since July 2009, we've asked flusurvey users to report their social contacts - this should help us link social mixing behaviour to risk of infection. We've seen in the pattern of estimated swine flu cases that school holidays have had a big impact on transmission, and we can look to see whether this can be explained by changes in contact patterns.

Some flusurvey users have been especially keen, and have recorded their social contacts almost every week. Below are shown how these change over time for a handful of these people (each colour being a different person).

There are clearly differences between people, and the variation makes it hard to see any trends over time. However, when we combine the reports from all users who have completed the contact survey on 12 or more occasions, much clearer patterns emerge:

The red line shows the "middle" person for each week, while the green and blue lines show where the upper and lower 25% fit in. We can see very clear changes at the end of the summer holiday, during school half term, and during the Christmas holiday period - at these times flusurvey users are away from work so make fewer social contacts.

All this ties in extremely nicely with the epidemic data, and, encouragingly, shows the usefulness of our simple contact surveys. We are interested in seeing how patterns will change now that people are back to work (and now that the snow has melted), so we'll keep and eye on this in the weeks to come.

Vaccination

A swine flu vaccine has been available since November, with health care workers and people in various high risk groups (e.g. pregnant women and those with underlying health conditions) initially given priority. The campaign requires GPs to identify patients for vaccination, and to arrange for them to attend their surgery - quite an organisational effort.

So, has it worked? We've been asking flusurvey participants to tell us whether or not they've been vaccinated, and why (or why not - it's just as important to know why people choose not to be vaccinated).

We've looked at people who, according to the backgroundquestionnaire, are in a "high risk" group (i.e. have some underlyinghealth condition) and at health care workers. Uptake isreasonably good in both these groups (around 50%), but is unsurprisingly low in the rest of thepopulation.

For the vaccine to make a difference, it needed to be given outquickly. Above, we see that vaccination steadily increased throughNovember and early December - certainly not as quickly as we would have liked. 

Lastly, we asked people why they chose to have or to avoid a vaccine. Sensibly, people choose to be vaccinated to protect themselves and those around them, while those in high risk groups also opt for the vaccine because of their health condition, although (not surprisingly) our definition of a high risk group, made before the pandemic kicked off, didn't always tally with the observed patterns.

Some people report concerns about vaccine side-effects (though initial information indicates that the vaccine is a pretty safe one), but in general people choose not to be vaccinated because they are not in swine flu high-risk groups.

Because of the timing of the vaccination campaign, our results show that it didn't happen quickly enough to make much difference to the epidemic as a whole. However, because vaccination was targeted at those who would get the most benefit, it probably protected vulnerable people during the later part of the epidemic.

It's clear that there are important lessons to be learnt from all of this about how to rapidly vaccinate a population - flusurvey data will continue to be used to help the health authorities understand what worked (and what didn't) and why.  

More flusurvey results 

The answer is that we can't know for sure - symptoms vary too much from person to person. The tool that we use to determine whether someone has flu-like-symptoms has been developed over several years by our collaborators in Holland, Belgium, Portugal and Italy. It correlates closely with physician-diagnosed seasonal flu (in technical terms it is quite specific to flu). It is possible that some people who recieve a "respiratory symptoms" diagnosis actually have swine flu (technically, the sensitivity of the diagnosis may not be ideal). People with swine flu may display a different range of symptoms to those that have normal seasonal flu, which is what our diagnosis is based on. As we collect more data, we may revise our definitions.

(If you feel ill and are worried that you might have contracted swine flu, then you should stay at home and contact the health services: click here for health service contact details).