There is no point to vaccinating against every disease out there.  Vaccines have a cost to produce and administer, and – although rare – can have risk(s).  So why vaccinate at all?

Vaccinations are recommended for diseases that are particularly severe, debilitating or have no effective treatment or cure.  Risk for exposure can also play a factor in whether or not vaccines are recommended.

Using rabies virus as an example:  Rabies is fatal 99.9% of the time – the extremely rare survivors had to be placed in a medically-induced coma while receiving anti-viral drugs, and they were lucky.  Generally all states have laws requiring pet(s) to be vaccinated against rabies, because household pets are considered a first-line barrier between pet owners and potentially rabid wildlife – protecting both the pet(s) and their owners!  For this reason, not all people are routinely vaccinated against rabies virus, but those that handle animals more – such as veterinarians, veterinary technicians and animal control workers – often are.

Vaccines will also be used to control – or, in the case of smallpox, eradicate – a disease in a population.  For a disease to spread, it needs to continue finding new hosts are not yet immune to it.  Therefore, when a community is vaccinated against that disease, it makes it harder to spread.  The reverse is also true – when a community is no longer vaccinated against that disease, there is a higher risk of outbreaks occurring. This is a concept called “herd immunity.”  As noted in another article, not all members of a community can be vaccinated – some are too ill or their individual risk is too high – but by vaccinating those that are healthy and can be vaccinated, the community as a whole can be better protected.

Vaccines may also have additional uses in the future.  For example, studies are being done to see if vaccines can be used to train the immune system to treat certain types of cancer!