Adenovirus is a virus that presents itself like flu or colds. It also can lead to very serious lung infections as the immune system is suppressed. There is no vaccine available to the general public. The US Army has a vaccine available to immunize its solders.
From the CDC: Adenoviruses are common causes of respiratory illness, but most infections are not severe. They can cause cold-like symptoms, sore throat, bronchitis, pneumonia, diarrhea, and pink eye (conjunctivitis). You can get an adenovirus infection at any age, but infants and people with weakened immune systems are more likely than others to develop severe illness from adenoviruses.
The problem for older adults with weakened immune systems is that could lead to pneumonia. I know of two people locally that have been hospitalize after starting with what just seemed like a cold. Adenovirus appears to be prevalent throughout the southeast. This particular version of adenovirus presents itself like symptoms of the flu or a severe cold.
To help keep your immune system up during the flu and cold season, I would suggest you read my several posts on viruses and the common cold. https://pandemicsurvivor.com/2014/10/24/treating-and-preventing-viral-infections/ and https://pandemicsurvivor.com/2012/03/30/vitamin-d-the-common-cold-and-rhinitis/ and https://pandemicsurvivor.com/2014/10/27/how-mom-and-dad-dealt-with-flu-and-colds/
In these posts, you will find that large amounts of vitamins A, D, and C in combination with zinc is the best solution. –Pandemic Survivor