The trivalent vaccine is the most commonly used vaccine and targets three flu virus strains; two flu A strains – H3N2 and H1N1 – as well as one flu B strain. There is also a quadrivalent flu shot that covers the same two flu A strains and the flu B strain found in the trivalent vaccine, but adds a second flu B strain as well.
“The current flu shot is not a loser and should not be benched as ineffective,” says Jorge Parada, MD, MPH, FACP, FIDSA, FSHEA, hospital epidemiologist and medical director of the Infection Prevention and Control program at Loyola University Health System. “While there was a mismatch due to a mutation in the H3N2 strain, there are actually two H3N2 strains in circulation, complicating the interpretation of the accuracy of the vaccine.”
The Centers for Disease Control (CDC) reports that flu activity is “high” or “widespread” in 43 states and call it an epidemic this season. Most of the cases are caused by the H3N2 strain. “Nearly one-third of circulating H3N2 virus match the strain found in the current vaccine, meaning the vaccine is doing its job,” says Parada. “One hundred percent of the H1N1 circulating strain matches that in the current vaccine, earning a touchdown or a bull’s eye for those keeping score.” However, to date, only a small portion of the flu cases reported to date have been identified as H1N1.
Two flu B strains are currently in circulation. “The dominant one accounts for 70 percent of flu B out there and it matches the strain in the trivalent vaccine making it very effective. The remaining flu B strain in circulation is a match to the second flu B strain found in the quadrivalent vaccine, making it a one hundred percent match for flu B this season,” says Parada. “The B strain regularly appears in January and February and the current flu vaccine will help build immunity,” he says. The CDC reports that February is still a very active month for the flu.
The real losers this flu season? Those who are not vaccinated. “The flu vaccine is readily available and affordable, even free in some areas. if you haven’t gotten your flu shot yet, get it now because the season lasts till late springtime," says Parada, professor of medicine at Loyola University Chicago Stritch School of Medicine. “Not being vaccinated greatly increases your chances of becoming ill not once but multiple times because every flu season there are multiple strains of flu circulating. Plus, every time you catch the flu you increase the chance that you may pass it along to a family member, friend or colleague, amplifying the problem.”
He advises everyone to wash hands thoroughly with soap and water or hand sanitizer to minimize risk plus stay away from ill individuals. Dr. Parada and Loyola have seen a large spike in flu cases at Loyola medical center and its many clinics. “Just in the last week Loyola had more than double the number of lab-confirmed cases of flu than we had during the peak week of last season – and it isn’t over yet,” he said.
For the sixth year in a row, Loyola has required that all employees, students, volunteers and even vendors receive the seasonal flu vaccination. “Firemen must wear fireproof gear and hospital staff need vaccinations to protect themselves and others from infectious diseases,” says Parada, who oversees the campaign at Loyola. Loyola is an academic medical center and is equipped to treat complex health problems.
“The biggest danger of the flu is that it worsens other medical conditions. It can exacerbate congestive heart failure and many other chronic illnesses,” says Parada. “Also, the flu can decrease the body’s ability to fight other infections that one might get while you have the flu, like pneumonia.” Pneumonia is a leading cause of death among the very old, very young and the chronically ill.
Dr. Parada urges everyone to get the flu vaccine if they are able. “To those who think there is no point because it is a mismatch, I answer that it is only a partial mismatch and it still offers protection for the many of the multiple flu strains circulating out there. To those who point to the mismatch as the cause for this year’s bad flu season, I answer then that only reinforces how important it is to get vaccinated, “says the infection control specialist with more than 25 years of experience. “First, imagine how much worse the flu would be if it was a complete mismatch. Second, most years there is no mismatch and high levels of vaccination can help reduce the impact of the flu on everyone.”
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