Researchers in other countries have found evidence that circulating strains of Bordetella pertussis have adapted to the acellular vaccine, and researchers today reported similar findings for the first time in US kids, based on genetic analysis of isolates from hospitalized children.
Infectious disease experts have been eyeing waning immunity from acellular pertussis vaccines as a contributor to increasing numbers of cases of pertussis (whooping cough) in several countries, and evidence is mounting that another factor fueling the outbreaks could be that the bacteria are adapting to the vaccine.
The US researchers, including a scientist from the US Centers for Disease Control and Prevention (CDC), described their findings in a letter in the New England Journal of Medicine.
So far, lab studies in Japan, France, and Finland have identified variants of B pertussis that are negative for pertactin, a virulence factor and an outer membrane protein that promotes adhesion to tracheal epithelial cells. Pertactin purified from B pertussis is a key component of the acellular pertussis vaccine.
Many countries switched from the whole-cell pertussis vaccine to the acellular version in the late 1990s because of a fairly high rate of minor side effects in the whole-cell vaccine.
However, in the face of rising pertussis levels, surveillance studies in the United States and other countries are finding a gap in protection in children who received doses of acellular vaccine. The CDC has said that pertussis cases are at their highest point since 1955.