When and if a major disaster comes our way we could all be homeless.

Survivors weakened by limited food, water, stress, lousy nutrition, poor sanitation and possibly crowded together will be ripe for far more than just H1N1 infection. Homeless people, even in these relatively normal times, are better than 30 times as likely to get pneumococcal pneumonia as the normal well housed and well fed population.

http://scienceblogs.com/mikethemadbiologist/2009/10/homelessness_and_streptococcus.php

Consider getting immunized for S. pneumoniae

I blame that on their crowded living conditions. Seriously.

Anyhow, it is worth looking into getting immunized even if you never expect to be living in crowded and unsanitary conditions like the homeless do.

If you really are thinking disasters/shelter living, you should do what most of the groups want their staff to do

Follow the Healthcare Workers Vaccination schedule

DPT, Varicella, Zoster, MMR, Flu, Possibly Pneumococcal, HepA, Hep B and Meningoccal (maybe)

See table 2 below

http://www.cdc.gov/mmwr/PDF/wk/mm5753-Immunization.pdf

IMO one of the best things about such vaccinations is that, unlike other protective measures that depend on chemicals, like hand sanitizer, or protective equipment, like masks, once immunized you don't need to do or carry anything special. Worse case, you might lose all your gear but your still protected. Also, given the years, often a lifetime, of protection vaccination is highly cost effective.

If your short on money, who isn't at least concerned about it, check with state and local health departments. They often get shipments that get used up quickly. If you know about it and show up at the right time you can often get it for free or at reduced price.