Viruses Are Not Easy to Get Rid Of

Liberia has created a night-time curfew in Monrovia and has quarantined a slum in that city in an effort to stem the spread of the ebola virus. At the same time, Kenya Airways has stopped flying to Sierra Leone and Liberia for the same reason--essentially quarantining those two countries. Ebola is scary because there is currently no immunization for it, and no certain treatment for it if you contract the disease. We have had immunizations for polio for half a century, however, and we still haven't quite rid ourselves of that disease. Why? Largely because there are populations where conflict upsets the process of vaccinating children. Pakistan is one of the last holdouts of polio, but a story in Nature today notes that the Congo had a recent brush with polio, as well.

The cause of an unusually severe outbreak of poliomyelitis that hit Congo in 2010 has been identified: a strain of poliovirus that sometimes resists the immune responses mounted by vaccinated people.

Fortunately, people who have recently received the live, oral polio vaccine, which provides the strongest immunity, are protected against the strain. Its spread in Congo was stopped by orally re-vaccinating the entire population of the surrounding areas.

However, a new study, published on 18 August in the Proceedings of the National Academy of Sciences1, suggests that a portion of those who receive the weaker, dead vaccine would have been vulnerable. This vaccine is now common in developed countries. What's more, the researchers who characterized the strain warn that something similar may appear again during the final stages of the global effort to eradicate polio.

Olen Kew, a virologist at the US Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, is less concerned. “The bottom line is that oral polio vaccine works wherever it is used properly — at high rates of coverage,” he says. “The Republic of Congo had a period of very low coverage because of civil unrest, and immunity gaps widened.”

This is the main point for all those parents who have the misguided view that vaccinations are worse for their children than the diseases against which the vaccinations protect their children: Get real!