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The native children of Alaska have always been vulnerable to pneumococcal diseases such as pneumonia and meningitis, despite the apparent success of a heptavalent childhood vaccine introduced in 2001. The vaccine all but wiped out invasive disease caused by seven specific serotypes, but other serotypes have emerged to take their place, say researchersresearchers.
Ongoing surveillance shows that rates of invasive disease among native Alaskan children under 2 years increased by 82% between the two surveillance periods 2001-3 and 2004-6. Most cases were of the pneumococcal serotypes not covered by the vaccine. Serotype 19A was the most common. Rates of disease among non-native Alaskan children remained low.
Experts worried about the prospect of serotype replacement even before the original seven valent vaccine was licensed, says an editorial (pp 1825-6). The resurgence of these serious infections in native Alaskan children could signal similar problems for less vulnerable populations elsewhere and ultimately threaten the otherwise “spectacular” success of the national vaccination programme.
New 13 valent vaccines are already in the pipeline, says the editorial. But they may have to be modified every five to 10 years until scientists develop a vaccine that protects children from all known serotypes of Streptococcus pneumoniae.