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When is a vaccine not effective?

Ahhhh… when you don’t get the vaccine?

Right, but also when there are multiple strains of an infectious microbe and the vaccine can’t protect you from them all. This is one challenge to producing effective vaccines and it actually happens every winter.

Did you know the flu vaccine won’t protect you from all the different flu strains that could emerge this winter?

Another example is the vaccine Prevnar which protects children and adults from middle ear infections and pneumonia caused by Streptococcus pneumoniae.

It’s a great vaccine, but this bacterium has more than 90 strains and the vaccine only protects against 7 of them. The result is strains which rarely caused disease are becoming prominent.

A recent AMA study reported when Alaskan children took Prevnar the rate of pneumoniae fell from 4 to 1.3 per thousand but within two years the rate doubled.

This is discouraging because here we make an effective vaccine yet our efforts are thwarted by strains not covered by the vaccine.

Luckily this is not the case for all vaccines. The ones we had as kids like polio, diphtheria and mumps work very well.

A vaccine being pushed by the federal government to protect kids against meningitis is also very stable.

But again, some vaccines just like the flu vaccine are limited by either a pathogen’s ability to mutate or by the mere fact that it has many strains. They include the AIDS virus and HPV which can lead to cervical cancer.

So Dave we microbiologists have lots of work ahead as we try to protect people from these wily pathogens.

I’m up for that – sounds like job security!