Influenza — what most of us call "the flu" — is a highly contagious viral infection of the respiratory tract. Flu season runs from October to May. It's best to get a flu vaccine as early in the season as possible. This gives the body a chance to build up immunity to protection from the flu. But getting a flu vaccine later in the season is still better than not getting the vaccine at all. But it's especially important that those in higher-risk groups get vaccinated to avoid health problems as a result of the flu.
MDHHS - Materials for the Current Influenza Season
Vaccines contain very small amounts of specific ingredients, all of which play necessary roles either in making the vaccine, or in ensuring that the vaccine is safe and effective. Thimerosal is a preservative used in multi-dose vials of the flu vaccine to keep them free from contamination, and contains an organic form of mercury called ethyl mercury. Ethyl mercury is not the same as methyl mercury, which may be found in fish and shellfish. Methyl mercury stays in the body and can make people sick, while thimerosal doesn't stay in the body. There is no evidence of harm caused by the low doses of thimerosal in vaccines.
Single-dose drug can shorten flu symptoms by about a day, studies suggest
Influenza flu is a very common and highly infectious disease caused by a virus. It can be very dangerous, leading to serious complications and death, especially for people in risk groups. In rare cases flu can kill people who are otherwise healthy. In the UK an average of people a year die from complications of flu, but in some years this can rise to over 10, people. Flu leads to hundreds of thousands of GP visits and tens of thousands of hospital stays a year.