A country vaccinates all of its poultry against Salmonella. The number of cases of Salmonella food poisoning falls, but it does not fall to zero. What is the best explanation?
The vaccine only protects poultry that are older than a few weeks
Salmonella can still be present on other foods and on dirty hands
Vaccinated poultry still release toxins into the meat that is eaten
People who eat vaccinated poultry become immune to the bacterium
252 exam-style questions on AQA GCSE Biology 3.1 Communicable diseases, covering 3.1.1 Communicable (infectious) diseases, 3.1.2 Viral diseases, 3.1.3 Bacterial diseases, 3.1.4 Fungal diseases, 3.1.5 Protist diseases, 3.1.6 Human defence systems, 3.1.7 Vaccination, 3.1.8 Antibiotics and painkillers, and 3.1.9 Discovery and development of drugs. Each one has a worked solution and a mark scheme showing where the marks go.