WASHINGTON (AP) _ A vaccine designed to prevent bacterial pneumonia also reduced the number of virus-related cases of the disease, according to research that indicates the two types of infection may interact.
In tests in more than 37,000 children in South Africa, the pneumococcal vaccine also prevented 31 percent of pneumonia associated with any of seven respiratory viruses, researchers said.
Their results were reported in this week's online edition of the journal Nature Medicine.
The discovery that the bacterial vaccine also blocks some viral illness indicates that ``bacteria and viruses can interact together to cause disease in humans,'' said Keith P. Klugman, a professor of infectious disease at Emory University in Atlanta who led the team of researchers.
He said the finding also indicates that children with severe pneumonia should have access to antibiotics.
Antibiotics attack bacteria but not viruses, so these drugs are not generally used in viral infections. If an illness results from a combination of bacteria and viruses, antibiotics might help by attacking the bacteria.
Pekka Nuorti, a medical epidemiologist with national immunization program at the Centers for Disease Control and Prevention, said some cases of pneumonia that are thought to be caused by a virus actually result from a combination of both infections.
``Therefore they're preventable by the vaccine,'' he said.
Michael Kurilla of the National Institute of Allergy and Infectious Diseases said that physicians long have had the impression that viral infections precede the development of potentially more severe bacterial infections.
``We believe in many cases of influenza, the damage the virus does to the lung sets up the opportunity for the bacteria to get in there,'' Kurilla said.
He said the new study suggests the opposite: the bacterial infection creating damage that allows for a viral infection to come in on top of it.
``What it may be saying is, these things can go wither way,'' said Kurilla.
The important thing, he said, is that the pneumococcal vaccine worked against the bacteria as well as nearly one-third of viral cases, a factor in considering the cost-benefit value of the vaccine.
Neither Kurilla nor Nuorti was a part of the research team.
In addition to pneumonia, the vaccine protects against other pneumococcal illnesses such as meningitis, blood infections and ear infections.
Klugman's paper notes that childhood vaccination has been shown to reduce pneumococcal illnesses in adults. It also suggests studies to determine whether the vaccine also reduces the incidence of pneumonia and influenza among adults.
The type of pneumococcal vaccine used in the tests has been in short supply in the United States. The government had recommended that doctors postpone the normal third and fourth doses for healthy children until supplies grow.
That recommendation was modified last week, advising doctors to go ahead with the third dose while deferring the fourth.
The vaccine is made by Wyeth Vaccines, which was a sponsor of Klugman's research. The research was also supported by the World Health Organization.