There is a new explanation of why we are seeing more cases of pertussis (whooping cough) in spite of high immunization rates among children:  the vaccine does not appear to be very effective against a new strain that was initially isolated in Japan, Finland, and France, and has now been identified in the U.S.  The AP’s Michael Stobbe puts things in perspective:

Whooping cough is a highly contagious disease that can strike people of any age but is most dangerous to children. It was once common, but cases in the U.S. dropped after a vaccine was introduced in the 1940s.

An increase in illnesses in recent years has been partially blamed on a version of the vaccine used since the 1990s, which doesn’t last as long. Last year, the CDC received reports of 41,880 cases, according to a preliminary count. That included 18 deaths.

The new study suggests that the new whooping cough strain may be why more people have been getting sick. Experts don’t think it’s more deadly, but the shots may not work as well against it.

In a small, soon-to-be published study, French researchers found the vaccine seemed to lower the risk of severe disease from the new strain in infants. But it didn’t prevent illness completely, said Nicole Guiso of the Pasteur Institute, one of the researchers.


Time to get back to the drawing board to develop a new pertussis vaccine.  In the meantime, because the current vaccine gives some protection against this pertussis variant (and better protection against the more typical strains), continued immunization of children and adults should still be a top public health priority.

Read report in the New England Journal of Medicine here.