Strep Vaccine Shows Promise in Early Trial

Confers immunity without serious side effects

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HealthDay Reporter

TUESDAY, Aug. 10, 2004 (HealthDayNews) -- Strep throat and the ever-unpopular throat culture to test for strep may one day be a thing of the past.

In a first step toward that goal, researchers report that a vaccine for Group A streptococcus performed well in a small, early trial designed to test for safety and efficacy.

"This vaccine included proteins from six different types of strep, and we found that it stimulated immunity to all the different types of strep," said study co-author Dr. Karen Kotloff, a professor of pediatrics and medicine at the Center for Vaccine Development at the University of Maryland School of Medicine in Baltimore. The results appear in the Aug. 11 issue of the Journal of the American Medical Association.

"This study opens the door to further testing and hopefully, in not too many years, we'll have a good, effective and safe vaccine for strep," Kotloff added.

Group A streptococcus is responsible for millions of infections every year. It's the bacterium responsible for strep throat and the skin infection impetigo. Group A strep can also cause more serious infections, such as pneumonia, meningitis, toxic shock syndrome and necrotizing fasciitis.

"We definitely need a Group A strep vaccine. It is a major disease entity," said Dr. Michael Pichichero, a professor of microbiology and immunology, pediatrics and medicine at the University of Rochester Medical Center in New York. Pichichero wrote an editorial about the study in the same issue of the journal.

The vaccine in the current study is made using pieces of a protein called M protein. M protein is found on the outside of Group A streptococcus bacteria, and it helps the bacteria hide from the human immune system, Kotloff explained. Eventually, the body detects the bacteria and creates antibodies to it. Because the M protein varies somewhat from strain to strain of Group A streptococcus, the researchers included pieces from six different strains.

The concern, however, is that sometimes the body overreacts to the strep bacteria and creates an autoimmune response that can cause rheumatic fever and other disorders. So, any vaccine designed to trigger the body to create antibodies to strep might theoretically also cause some people to have a serious autoimmune reaction.

In clinical trials of a different protein-based vaccine in the 1960s, siblings of children who had rheumatic fever were vaccinated. Some of these children went on to develop rheumatic fever, presumably because of the vaccine, and the trials were halted, Pichichero said.

"We presume this product has eliminated the components that produced cross-reactive antibodies in the past," said Pichichero, but he added that researchers need to proceed with caution.

In the current study, Kotloff and her colleagues tested the vaccine on 28 healthy adults. All received three doses of the vaccine, but in varying strengths: eight received a dose of 50 micrograms; 10 were given 100 micrograms, and 10 were given 200 micrograms.

For those on the lower dose, the second dose was given 28 days after the initial and the third was given 56 days after the first vaccination. At the higher strengths, the second and third doses were administered on days 28 and 112.

The vaccinations were well-tolerated; no one had any serious side effects, and no one developed rheumatic fever, the researchers said.

All of the study volunteers had an increase in immunity to Group A strep. Those who received the highest dose also had the highest levels of immunity.

"We saw nice immune responses in adults," said Kotloff, who added, "There's a good chance that when you get into populations that haven't been exposed, like small children, the same thing will happen."

In the study, the authors wrote that very large studies of 10,000 to 60,000 people would need to be done before any vaccine could be approved for mass use.

Pichichero added that along with this vaccine, other vaccines for Group A strep are also being tested.

Another study in the same issue of the journal, however, examines a troubling possibility -- that eliminating one bacteria might allow another to flourish.

Israeli researchers compared the presence of a different type of streptococcus bacteria, Streptococcus pneumoniae, to the presence of another bacteria, Staphylococcus aureus, in children. S. aureus is one of the bacteria that are developing resistance to many antibiotics, the study reported.

The researchers found children who didn't carry S. pneumoniae were almost twice as likely to be carrying S. aureus. The authors said these findings should prompt further investigation, particularly as the use of a vaccine for S. pneumoniae (pneumococcal vaccine) becomes more widespread.

"When a new effective vaccine is studied, in addition to the direct effect of the vaccine on the rate of the specific bacteria, the indirect effect on other bacteria living in the same area should be studied," said Dr. Gili Regev-Yochay, an infectious disease specialist at Sheba Medical Center in Ramat-Gan and a study co-author.

More information

To learn more about Group A strep, visit the U.S. Centers for Disease Control and Prevention.

SOURCES: Karen Kotloff, M.D., professor, pediatrics and medicine, Center for Vaccine Development, University of Maryland School of Medicine, Baltimore; Michael Pichichero, M.D., professor, microbiology and immunology, pediatrics and medicine, University of Rochester Medical Center, Rochester, N.Y.; Gili Regev-Yochay, M.D., infectious disease specialist, Sheba Medical Center, Ramat-Gan, Israel; Aug. 11, 2004, Journal of the American Medical Association

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