Pneumonia Bug Evades Vaccine?

Bugs that cause childhood pneumonia and meningitis have evolved to evade vaccines by swapping bits of their genome with other bacteria, according to a study published Sunday.

The findings, published in Nature Genetics, show how quickly these life-threatening pathogens can disguise themselves with borrowed genetic decoys, and how hard it is for medicine to keep up.

Diseases caused by Streptococcus pneumoniae are thought to kill over a million young children around the world each year.

Vaccines that protect against these so-called pneumoccoccal infections are designed to recognize a material on the outer surface of a bacterium's cell called polysaccharide.

Each of over 90 kinds, or "serotypes", of these bacteria have a different polysaccharide coating.

In 2000, a vaccine that targeted seven serotypes proved highly effective when introduced in the United States. The same formula — which also prevented transmission from children to adults — was adopted in Britain.

Over time, however, the vaccine worked less well, so researchers led by Rory Bowden at the University of Oxford set out to discover why.

Combining cutting-edge genetic analysis with epidemiology, which examines how disease spreads, they found that the deadly pathogens escaped detection by swapping genes with other, slightly different, bacteria.