MONTREAL — U.S. plans for an influenza virus pandemic should include a strong recommendation for bacterial pneumonia vaccination, as this measure has been shown to reduce influenza mortality by up to 50%, said Dr. Keith Klugman.
“In the U.S. pandemic plan, there is little mention of bacterial vaccines. I believe their role is significant and has not been considered up until now,” he said at an international conference on community-acquired pneumonia.
Although the influenza virus alone can be fatal, the risk of death is greater with secondary pneumococcal infection, said Dr. Klugman, professor of infectious diseases and the William H. Foege Chair of Global Health at Emory University, Atlanta.
“The combination of bacterial superinfection and influenza is highly fatal. It's a huge problem, and it's not a small part of influenza mortality and morbidity,” he said in an interview.
Evidence that pneumococcal infection played a major role in the 1918 influenza pandemic “is substantial, but seems to have been forgotten,” Dr. Klugman recently wrote in a letter to the editor (Science 2007;316:49–50), citing historical evidence of culturable pneumococci in the blood of at least half of the survivors and victims of influenza (Br. Med. J. 1919;1:3–5; JAMA 1918;71:1735).
A randomized, controlled trial by Dr. Klugman and his colleagues has shown that, in children, vaccination against the pneumococcal bacteria results in a 31% decrease in pneumonias associated with respiratory viruses (Nat. Med. 2004;10:811–3). “Because of the vaccine, they are not getting the superinfection that brings them to the hospital,” he said at the meeting, sponsored by the International Society of Chemotherapy. “People have known for years that there can be bacterial superinfections with influenza, but they just didn't realize how common they were.”
The 23-valent pneumococcal polysaccharide vaccine (PPV 23) is recommended in adults older than 65 years, but giving the 7-valent pneumococcal conjugate vaccine (PCV 7) to children is more protective against bacterial pneumonia in adults, Dr. Klugman said.
Data from the Centers for Disease Control and Prevention show that adult infections with the 7 pneumococcal strains covered in the children's vaccine have decreased, while infections from the other 16 strains covered by the adult vaccine have increased. “The burden of disease in adults has been impacted more by giving the conjugate vaccine to children than by giving the 23-valent vaccine to adults,” he said.
This has led some investigators to ask whether adults might benefit by being immunized using the children's conjugate vaccine. (See box.)
A new study (Lancet 2007;369:1179–86) has shown that vaccinating children protects adults against all (not just bacteremic) pneumococcal pneumonia, he said.
Should Adults Get the Kids' Vaccine?
Is there a role for giving the children's conjugate vaccine to adults?
In a recent study (Vaccine 2007;25:4029–37), immunogenicity in elderly patients (aged 70–79 years) given the children's dose of conjugate vaccine was “nothing to get overly excited about,” Dr. Klugman said.
A study presented at the 2006 International Symposium on Pneumococci and Pneumococcal Diseases by Dr. Andrés de Roux of the Universitat Autònoma de Barcelona and colleagues suggested that the administration of the children's conjugate vaccine to elderly patients within 1 year of giving them the polysaccharide vaccine could actually suppress immunity. “It seems the adult vaccine interferes with the response to the conjugate, which … means we can't simply give the conjugate to people who have previously had the [PPV 23]. … It seems that certainly the conjugate needs to be given before the 23-valent,” Dr. Klugman said.
A new conjugate vaccine that covers more strains than the current one will eventually replace the PPV 23 for adults, he predicted.