US citizens began receiving the newly developed swine flu vaccine this week in the form of a nasal(鼻の)spray. The injection is expected to be ready next week. About 2.2 million doses of the nasal spray are already available and being given to healthcare workers and healthy children above the age of 2. Pregnant woman, people with asthma, and those with chronic medical conditions are being advised to avoid the nasal spray and wait for the injection. The US hopes to inoculate as many as 250 million people against the illness by the end of the year. This past June, the UN World Health Organization declared that the H1N1 virus was causing an influenza pandemic.