Impact of vaccines on drug resistant microbes

Voices for Vaccines recently highlighted an opinion piece by Peter I. Hartsock, submitted to the Washington Post in which Hartsock argued that vaccines are an invaluable tool in our attempts to control organisms resistant to treatment.

A particularly important benefit of vaccination is its critical effect on the evolution of disease. A growing number of deadly maladies are becoming resistant to drugs. Every infection prevented through vaccines means less need for medical treatments for that type of infection. This, in turn, helps reduce the speed at which diseases “adapt” to and render medications ineffective.

Vaccine critical voices from the forums at Mothering.com (MDC) have questioned whether this statement is just dancing around the issues since, one person claimed, “but VACCINES are causing the same phenomenon!”*

Are non-vaccine strains, and strains that mutate to evade vaccines a problem significant enough to denounce the major successes vaccines have had?

I’m going to try to discuss these one at a time over several blog posts, since it’s a fascinating topic to me. I’ll start with the PCV vaccine.

The person I quoted above included a link to a 2007 news report about the emergence of drug resistant Streptococcus pneumoniae strain 19A, a strain that was not included among the original 7 strains of the PCV (PCV7) vaccine in 2000. This strain was being actively monitored by the time the 2007 news report surfaced, and within 2 years the PCV7 vaccine was replaced with PCV13, which covered strain 19A and 5 other strains that had not be included in PCV7.

By 2013, a study in Israel showed a total decrease of 77% of cases of ear infections caused by S. pneumoniae, and 60% decrease in ear infections of all types, without noting any increase in ear infections caused by non-vaccine strains of S. pneumoniae. This is important because the vaccine protects against only 13 predominant forms of 90 total known strains. The concern has been that other strains will fill the niche when those 13 vaccine strains are eliminated. So far, this hasn’t been an issue.

A study conducted in 2011 in the US specifically monitored the impact of vaccines on antimicrobial resistant strains of S. pneumoniae. Infections with microbial resistant strains were reduced by 64% for children under 5 and 45% for adults over 65 following the introduction of PCV7 and the recent (at that time very recent) transition to PCV13.

Since S. pneumoniae is a bacterium that has been a common cause of minor infections as well as serious, invasive illness, it has played a major role in clinical antibiotic use in the developed world. The reduction of these infections by antibiotics, as I’ve highlighted, have reduced the need for antibiotics and thus offer hope to reduce the further development of antibiotic resistance. Other vaccines that prevent primary bacterial infections are Hib and meningococcal vaccines.

Vaccines don’t just play a role in reducing these primary infections, but they also eliminate secondary bacterial infections following preventable viral infections such as chickenpox, measles and influenza.

While there are some potential concerns about tricky organisms mutating to evade vaccines, specifically influenza, and possibly pertussis, these concerns are minimal compared to the dramatic successes of vaccines in preventing infections and thus reducing drug resistance.

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