There are two types of vaccine: a live attenuated vaccine (nasal spray) and an inactivated vaccine (shot). You cannot get the flu from getting the flu shot because it has inactivated virus (killed virus with heat or chemicals). The immunity from the vaccines is limited, and vaccinations must be repeated yearly. It is recommended that all people older than 6 months receive an annual vaccination. Developed new in 2013-2014 was a vaccine for people with egg allergy : recombinant hemagglutinin influenza vaccine (RIV). Although the CDC encourages that any adult who wants to decrease the chance of getting the flu get the influenza vaccine, certain high-risk groups are recommended to always get the annual flu vaccine . Adults over 50 years of age are considered to be at high risk and should receive the yearly influenza vaccination.
As described above, melatonin is extremely safe. It is a hormone that your body makes naturally. Its use in a supplement form is also believed to be quite safe. It is not habit-forming and you will not become "addicted" or dependent upon it. Therefore, if you find it to be helpful in improving your sleep, you may use it on a nightly basis without fear of adverse consequences. There is some caution advised in children and pregnant women due to its potential effects on other hormones. Side effects are not usually problematic, but these will resolve with discontinuation of the medication.