> All UK chickens are vaccinated against Salmonella
I think it's most, but not all, chickens. Vaccination is part of the red lion quality brand mark, and approx 80% of birds are part of that; and many farmers not part of it vaccinate too.
Vaccination isn't mandatory. There are some vigorous testing requirements as part of the National Control Programme for salmonella.
Maybe I'm wrong though, has this changed recently?
https://www.gov.uk/government/uploads/system/uploads/attachm...
> 1.1.3 The Advisory Committee on Microbiological Safety of Food (an expert independent group which advises the Food Standards Agency) considered Salmonella in eggs and reported on its findings in May 20011 and considered that the widespread vaccination of egg laying flocks against S. Enteritidis combined with improved flock hygiene measures had had a significant effect on the prevalence of Salmonella contamination of eggs and on salmonellosis in humans. In the UK a voluntary industry operated scheme (British Egg Industry Council) Lion Quality requires its members to vaccinate their layer flocks and to operate to specified hygiene standards. About 85% of egg production belongs to the Lion Quality scheme. In addition many producers who are not members of the scheme also vaccinate their flocks on a voluntary basis.