(RxWiki News) Each year's flu vaccine is a different gamble: a combination of the three influenza strains that scientists believe are most likely to circulate that year. But the odds could improve.
A recent industry-funded study found that an intranasal influenza vaccine containing four flu strains tested in a clinical trial was as safe and effective as the three-strain vaccines.
"Get your flu vaccine every year."
Stan Block, MD, a pediatrics professor at the University of Kentucky College of Medicine and the University of Louisville School of Medicine, led the trial along with Robert Belshe, MD, a professor of infectious diseases at Saint Louis University School of Medicine and director of the Center for Vaccine Development at Saint Louis University.
Currently, flu vaccines include two influenza A strains and one influenza B strain.
Until recently, manufacturers have not been able to include both strains of the influenza B in the vaccine, forcing researchers to basically guess which one would show up that year.
Receiving a vaccine with one strain for influenza B will not protect people against the other influenza B strain. The two influenza B strains exist because a single influenza B virus split into two lineages in the 1980s and have evolved into different strains.
"It has not been possible to predict which strain has circulated," Dr. Belshe said. "In the last 10 years, we predicted right five times. So you can flip a coin and do as well.”
Now, however, a four-strain vaccine has been made and researchers needed to determine whether it offered the same level of protection for the various strains as the three-strain vaccine.
For the study, approximately 2,300 children between the ages of 2 and 17 were randomly split up to receive one of three vaccines. Sixty percent of the participants received the new four-strain vaccine.
Twenty percent received a three-strain vaccine with one of the influenza B strains, and the other 20 percent received a different three-strain vaccine with the other influenza B strain.
Children aged 2 to 8 years old received one dose of the vaccine with a booster dose one month later. Those aged 9 to 17 received only a single dose of the vaccine.
The researchers tested the participants' immune responses with blood samples one month after the last dose and compared adverse events in all the groups to determine the safety of the new vaccine.
The researchers found that the new vaccine was "noninferior" to the two currently used vaccines, which means it was just as effective at causing the body to produce antibodies that would be able to fight the flu immediately if the child was infected with the virus.
The side effects seen among children who had all three vaccines were similar, primarily consisting of stuffy noses common with the FluMist nasal vaccine and low grade fevers, which often occur with other vaccines as well.
The four-strain vaccine appeared just as safe as the three-strain vaccine, though fevers were more common with the four-strain vaccine.
The US Food and Drug Administration approved the four-strain vaccine, called a quadrivalent influenza vaccine, on February 28 for people between the ages of 2 and 49.
“The bottom line is adding another strain to make a quadrivalent vaccine improves our ability to protect against flu and doesn’t reduce the body’s immune response to the other strains,” Dr. Belshe said.
“It should bring us better protection because there’s less guesswork than in the standard trivalent vaccine," he said.
The vaccine may be available during the 2013-2014 flu season depending on when it is reviewed by the Advisory Committee on Immunization Practices, the body of the Centers for Disease Control and Prevention that makes vaccination recommendations.
Belshe said the researchers are also working on developing an injection version of the quadrivalent vaccine.
The cost of the new vaccine has not been made available. However, the trivalent (three-strain) vaccines have previously been made available at drug stores and doctors offices for approximately $20 to $30.
The study was published online April 3 in the Pediatric Infectious Disease Journal. The research was funded by MedImmune, which manufacturers this quadrivalent flu vaccine.
Dr. Belshe has received research grants and speaking and consulting fees from MedImmune, who sponsored this study.